Phase Behavior of Cholesterol-Containing Binary Membrane of an Ether-Linked Phospholipid, Dihexadecylphosphatidylcholine

The thermotropic phase behavior of the cholesterol (Chol)-containing binary membrane of dihexadecylphosphatidylcholine (DHPC) was investigated as a function of the mole fraction of Chol Xch by DSC and fluoresce spectroscopy using 6-propionyl-2-(N,N-dimethylamino)naphthalene (Prodan). The main-transition enthalpy Hm was almost constant at Xch < ca. 0.05, but it decreased almost linearly with increasing Xch above 0.05 until it reached 0 at Xch = ca. 0.50, suggesting that the interaction between DHPC and Chol is relatively weaker than that between dipalmitoylphosphatidylcholine (DPPC) and Chol. The Prodan fluorescence spectra changed depending on the phase state, which was characterized by the wavelength at the emission maximum. Particularly, the two-phase state of the interdigitated (LβI) and non-interdigitated gel (Lβ) was sensitively detected as the superposition of the two elementary spectra corresponding to each phase state, allowing us to explain the Xch dependent non-linear behavior of the Chol-induced Lβ phase by introducing a proportionality factor ξ(Xch) and by assuming a simple probabilistic process. By comparing the phase diagram constructed for the DHPC Chol binary membrane with that for the DPPC Chol binary bilayer, a difference was observed in the minimum Xch value for the entire formation of the liquid ordered (Lo) phase. This difference could be explained in terms of the hydrophobic mismatch at the bilayer midplane by taking into account the difference in the capability of hydrogen bonding with the 3β-OH group of Chol due to the presence or absence of the carbonyl oxygens at the glycerol backbone.

エーテル結合型リン脂質ジヘキサデシルホスファチジルコリン-コレステロール混合二分子膜の熱的相挙動を示差走査熱量測定と蛍光プローブ測定から調査した．コレステロール添加は指組み構造ゲル相の形成を抑制した．エステル結合型脂質ジパルミトイルホスファチジルコリン-コレステロール混合二分子膜系の相図との比較から，脂質頭部のカルボニル炭素の有無が二分子膜中における両分子の混和性に大きな影響を与えることが明確となった．


Ligand partitioning into lipid bilayer membranes under high pressure: implication of variation in phase-transition temperatures

The variation in phase-transition temperatures of dipalmitoylphosphatidylcholine (DPPC) bilayer membrane by adding two membrane-active ligands, a long-chain fatty acid (palmitic acid (PA)) and an inhalation anesthetic (halothane (HAL)), was investigated by light-transmittance measurements and fluorometry. By assuming the thermodynamic colligative property for the bilayer membrane at low ligand concentrations, the partitioning behavior of these ligands into the DPPC bilayer membrane was considered. It was proved from the differential partition coefficients between two phases that PA has strong affinity with the gel (lamellar gel) phase in a micro-molal concentration range and makes the bilayer membrane more ordered while HAL has strong affinity with the liquid crystalline phase in a milli-molal concentration range and does the bilayer membrane more disordered. The transfer volumes of both ligands from the aqueous solution to each phase of the DPPC bilayer membrane showed that the preferential partitioning of the PA molecule into the gel (lamellar gel) produces about 20% decrease in transfer volume as compared with the liquid crystalline phase, whereas that of the HAL molecule into the liquid crystalline phase does about twice increase in transfer volume as compared with the gel (ripple gel) phase. Furthermore, changes in thermotropic and barotropic phase behavior of the DPPC bilayer membrane by adding the ligand was discussed from the viewpoint of the ligand partitioning. Reflecting the contrastive partitioning of PA and HAL into the pressure-induced interdigitated gel phase among the gel phases, it was revealed that PA suppresses the formation of the interdigitated gel phase under high pressure while HAL promotes it. These results clearly indicate that each phase of the DPPC bilayer membrane has a potential to recognize various ligand molecules.

ジパルミトイルホスファチジルコリン(DPPC)二分子膜の相転移温度への2種類の膜活性リガンド(麻酔薬ハロセン，脂肪酸パルミチン酸)の効果を調べた．DPPC二分子膜の前転移および主転移は，ハロセン添加により降下，パルミチン酸添加により逆に上昇し，加圧は相転移を温度を共に上昇させた．熱力学的解析からハロセンは液晶相，パルミチン酸はラメラゲル相に親和性を有し，ハロセン添加により液晶相が膨張し，パルミチン酸添加によりゲル相が収縮することがわかった．また，ハロセンは高圧力下における指組みゲル相形成を促進し，パルミチン酸は逆に抑制した．指組みゲル相を含む相転移挙動へのリガンド効果についての議論が熱力学観点からなされた．


Thermotropic and barotropic phase transitions on diacylphosphatidylethanolamine bilayer membranes

The bilayer phase transitions of four diacylphosphatidylethanolamines (PEs) with identical two saturated acyl chains (Cn = 12, 14, 16 and 18) and two PEs with identical two unsaturated acyl chains containing a different kind of double bonds were observed by differential scanning calorimetry under atmospheric pressure and light-transmittance measurements under high pressure. The temperature-pressure phase diagrams for these PE bilayer membranes were constructed from the obtained phase-transition data. The saturated PE bilayer membranes underwent two different phase transitions related to the liquid crystalline (Lα) phase, the transition from the hydrated crystalline (Lc) phase and the chain melting (main) transition, depending on the thermal history. Pressure induced the change in the gel-phase stability of the bilayer membranes of PEs with longer chains at a low pressure. Comparing the thermodynamic quantities of the saturated PE bilayer membranes with those of diacylphosphatidylcholines (PC) bilayer membranes, the PE bilayer membranes showed higher phase-transition temperatures and formed more stable Lc phase, which originates from the strong interaction between polar head groups of PE molecules. On the other hand, the unsaturated PE bilayer membranes underwent the transition from the Lα phase to the inverted hexagonal (HII) phase at a high temperature and this transition showed small thermodynamic quantities but high-pressure responsivity. It turned out that the kind of double bonds markedly affects both bilayer-bilayer and bilayer-nonbilayer transitions and the Lα/HII transition is a volume driven transition for the reconstruction of molecular packing. Further, the phase-transition behavior was explained by chemical potential profiles of bilayer phases.

4種類の飽和ホスファチジルエタノールアミン(PE)および2種類の不飽和PEが形成する二分子膜の温度および圧力誘起相転移を調査した．飽和PE二分子膜は熱履歴に依存して水和結晶相/液晶相転移およびゲル相/液晶相(主)転移を示し，長鎖飽和PE二分子膜においては高圧力下でゲル相の安定性が変化した．熱力学量から，飽和PE二分子膜は同鎖長のホスファチジルコリン(PC)二分子膜よりも顕著に安定な水和結晶相を形成することがわかった．他方，不飽和PE二分子膜は，液晶相から逆ヘキサゴナル相への二分子膜/非二分子膜転移を誘起した．熱力学的な考察から，この転移は体積駆動の転移であることを示した．

Biochimica et Biophysica Acta (BBA) - Biomembranes


How Does Acyl-chain Length Affect Thermotropic Phase Behavior of Saturated Diacylphosphatidylcholine-chloresterol Binary Bilayers?

Thermotropic phase behavior of diacylphosphatidylcholine (CnPC) cholesterol binary bilayers (n = 14 16) was examined by fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and differential scanning calorimetry. The former technique can detect structural changes of the bilayer in response to the changes in polarity around Prodan molecules partitioned in a relatively hydrophilic region of the bilayer, while the latter is sensitive to the conformational changes of the acyl chains. On the basis of the data from both techniques, we propose possible temperature T cholesterol composition Xch phase diagrams for these binary bilayers. A notable feature of our phase diagrams, including our previous results for C17PC and C18PC, is that there is a peritectic-like point around Xch = 0.15, which can be interpreted as indicating the formation of a 1:6-complex of cholesterol and CnPCs within the binary bilayer irrespective of the acyl chain length. We could give a reasonable explanation for such complex formation using the modified superlattice view. Our results also showed that the Xch value of the abolition of the main transition is almost constant for n = 14 17 (ca. 0.33), while it increases to ca.0.50 for n = 18. By contrast, a biphasic n-dependence of Xch was observed for the abolition of the pretransition, suggesting that there are at least two antagonistic n-dependent factors. We speculate that this could be explained by the enhancement of the van der Waals interaction with increases in n and the weakening of the repulsion between the neighboring headgroups with decreases in n.


Volumetric characterization of ester- and ether-linked lipid bilayers by pressure perturbation calorimetry and densitometry

We investigated the thermotropic volume behavior of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and dihexadecylphosphatidylcholine (DHPC) membranes using pressure perturbation calorimetry (PPC) and densitometry. The ln φ(2) vs temperature curves (φ(2): apparent molar volume of phospholipid) obtained from the PPC data using an analysis method that we developed agreed with the results from the density measurements for these lipids within the relative difference of about 0.62%. From those curves, the volume changes with the main transition were estimated at 18.0±0.49, 23.5±2.33 and 23.0±0.33 cm(3) mol(-1) for DMPC, DPPC and DHPC, respectively. For DPPC and DMPC, the average volume per methylene group of the hydrocarbon chains v(CH2) calculated by referring to the procedure by Nagle and Wilkinson was consistent with the previous result, which indicates that the DPPC bilayer in the gel state has denser hydrophobic bilayer core than the DMPC bilayer. For DHPC, the volume of the headgroup region v(H) was calculated to be 244 Å(3) by assuming that v(CH2) of DHPC equals that of DPPC above 45°C. This value was comparable to that of DPPC when the volume of the carbonyl groups was considered, which may signify that there is no significant conformational difference in the polar headgroups of both phospholipids. However, it was suggested from the consideration on v(H) of DHPC at 20°C that expansion of the headgroup region should occur as the interdigitated structure is formed, which means some conformational change of the headgroup region is induced by the interdigitation.


Morphological Change of Vesicle Particle can Produce a Peculir Stepwise Transition in Dipalmitoylphosphatidylglycerol Bilayer at High NaCl Concentration


Intrinsic interaction mode of an inhalation anesthetic with globular proteins: a comparative study on ligand recognition


Thermotropic and Barotropic Phase Transitions of Dialkyldimethylammonium Bromide Bilayer Membranes: Effect of Chain Length

The bilayer phase transitions of dialkyldimethylammonium bromides (2C(n)Br; n = 12, 14, 16) were observed by differential scanning calorimetry and high-pressure light-transmittance measurements. Under atmospheric pressure, the 2C(12)Br bilayer membrane underwent the stable transition from the lamellar crystal (L(c)) phase to the liquid crystalline (L(α)) phase. The 2C(14)Br bilayer underwent the main transition from the metastable lamellar gel (L(β)) phase to the metastable L(α) phase in addition to the stable L(c)/L(α) transition. For the 2C(16)Br bilayer, moreover, three kinds of phase transitions were observed: the metastable main transition, the metastable transition from the metastable lamellar crystal (L(c(2))) phase to the metastable L(α) phase, and the stable lamellar crystal (L(c(1)))/L(α) transition. The temperatures of all the phase transitions elevated almost linearly with increasing pressure. The temperature (T)-pressure (p) phase diagrams of the 2C(12)Br and 2C(14)Br bilayers were simple, but that of the 2C(16)Br bilayer was complex; that is, the T-p curves for the metastable main transition and the L(c(2))/L(α) transition intersect at ca. 25 MPa, which means the inversion of the relative phase stability between the metastable phases of L(β) and L(c(2)) above and below the pressure. Moreover, the T-p curve of the L(c(2))/L(α) transition was separated into two curves under high pressure, and as a result, the pressure-induced L(c(2P)) phase appeared in between. Thermodynamic quantities for phase transitions of the 2C(n)Br bilayers increased with an increase in alkyl-chain length. The chain-length dependence of the phase-transition temperature for all kinds of transitions observed suggests that the stable L(c(1))/L(α) transition incorporates the metastable L(c(2))/L(α) transition in the bilayers of 2C(n)Br with shorter alkyl chains, and the main-transition of the 2C(12)Br bilayer would occur at a temperature below 0 °C.


Prodan fluorescence detects the bilayer packing of asymmetric phospholipids

The bilayer phase behavior of asymmetric phospholipids, palmitoylstearoylphosphatidylcholine (PSPC) and stearoylpalmitoylphosphatidylcholine (SPPC), with different vesicle sizes (large multilamellar vesicle (LMV) and giant multilamellar vesicle (GMV)) was investigated by fluorescence spectroscopy using a polarity-sensitive fluorescent probe Prodan under high pressure. The results were compared with those of a symmetric phospholipid, diheptadecanoyl PC (C17PC). The difference in phase transitions of the PSPC and SPPC bilayers and in thermodynamic quantities of the transitions was hardly observed between LMV and GMV as the case of the C17PC bilayer. On the other hand, the Prodan fluorescence showed clear differences between LMV and GMV of the asymmetric PC bilayers. From the second derivative of Prodan fluorescence spectra, the three dimensional image plots in which we can clearly see the location of Prodan in the bilayer membrane as blue valleys were constructed for LMV and GMV under high pressure. We revealed from the plots that the bilayer packing is significantly dependent on not only the vesicle size but also the acyl-chain asymmetry of PC molecule in addition to the phase states. It was found that the packing of the gel phases of the asymmetric PC bilayers is weaker than that of the symmetric PC bilayer, and the size of vesicle affects the packing of the interdigitated gel phase the most markedly among three gel phases. This study suggests that the Prodan molecules can detect the effect of vesicle size on the phase states for the asymmetric PC bilayers, and they become a useful indicator for various membrane properties, especially bilayer interdigitation.


Hydrostatic Pressure Reveals Bilayer Phase Behavior of Dioctadecyldimethylammonium Bromide and Chloride

Bilayer phase transitions of dioctadecyldimethylammonium bromide (2C(18)Br) and chloride (2C(18)Cl) were observed by differential scanning calorimetry and high-pressure light-transmittance measurements. The 2C(18)Br bilayer membrane showed different kinds of transitions depending on preparation methods of samples under atmospheric pressure. Under certain conditions, the 2C(18)Br bilayer underwent three kinds of transitions, the metastable transition from the metastable lamellar crystal (L(c(2))) phase to the metastable lamellar gel (L(β)) phase at 35.4 °C, the metastable main transition from the metastable L(β) phase to the metastable liquid crystalline (L(α)) phase at 44.5 °C, and the stable transition from the stable lamellar crystal (L(c(1))) phase to the stable L(α) phase at 52.8 °C. On the contrary, the 2C(18)Cl bilayer underwent two kinds of transitions, the stable transition from the stable L(c) phase to the stable L(β) phase at 19.7 °C and the stable main transition from the stable L(β) phase to the stable L(α) phase at 39.9 °C. The temperatures of the phase transitions of the 2C(18)Br and 2C(18)Cl bilayers were almost linearly elevated by applying pressure. It was found from the temperature (T)-pressure (p) phase diagram of the 2C(18)Br bilayer that the T-p curves for the main transition and the L(c(1))/L(α) transition intersect at ca. 130 MPa because of the larger slope of the former transition curve. On the other hand, the T-p phase diagram of the 2C(18)Cl bilayer took a simple shape. The thermodynamic properties for the main transition of the 2C(18)Br and 2C(18)Cl bilayers were comparable to each other, whereas those for the L(c(1))/L(α) transition of the 2C(18)Br bilayer showed considerably high values, signifying that the L(c(1)) phase of the 2C(18)Br bilayer is extremely stable. These differences observed in both bilayers are attributable to the difference in interaction between a surfactant and its counterion.


Application of pressure perturbation calorimetry to the aqueous system of phospholipid vesicle dispersion


Packing state in bilayer membranes of diacylphosphatidylcholines with varying acyl chain lengths under high pressure


Effect of Vesicle Size on the Prodan Fluorescence in Diheptadecanoylphosphatidylcholine Bilayer Membrane under Atmospheric and High Pressures

The bilayer phase behavior of diheptadecanoylphosphatidylcholine (C17PC) with different vesicle sizes (large multilamellar vesicle (LMV) and giant multilamellar vesicle (GMV)) was investigated by fluorescence spectroscopy using a polarity-sensitive fluorescent probe Prodan under atmospheric and high pressures. The difference in phase transitions and thermodynamic quantities of the transition was hardly observed between LMV and GMV used here. On the contrary, the Prodan fluorescence in the bilayer membranes changed depending on the size of vesicles as well as on the phase states. From the second derivative of fluorescence spectra, the three-dimensional image plots in which we can see the location of Prodan in the bilayer membrane as blue valleys were constructed for LMV and GMV under atmospheric pressure. The following characteristic behavior was found: (1) the Prodan molecules in GMV can be distributed to not only adjacent glycerol backbone region, but also near bulk-water region in the lamellar gel or ripple gel phase; (2) the blue valleys of GMV became deeper than those of LMV because of the greater surface density of the Prodan molecules per unit area of GMV than LMV; (3) the liquid crystalline phase of the bilayer excludes the Prodan molecules to a more hydrophilic region at the membrane surface with an increase in vesicle size; (4) the accurate information as to the phase transitions is gradually lost with increasing vesicle size. Under the high-pressure condition, the difference in Prodan fluorescence between LMV and GMV was essentially the same as the difference under atmospheric pressure except for the existence of the pressure-induced interdigitated gel phase. Further, we found that Prodan fluorescence spectra in the interdigitated gel phase were especially affected by the size of vesicles. This study revealed that the Prodan molecules can move around the headgroup region by responding not only to the phase state but also to the vesicle size, and they become a useful membrane probe, detecting important membrane properties such as the packing stress.


Pressure Study on Symmetric and Asymmetric Phospholipid Bilayers: Effect of Vesicle Size on Prodan Fluorescence

The bilayer phase behavior of symmetric and asymmetric phosphatidylcholines (PCs), 1,2-diheptadecanoyl-PC (C17PC), 1-palmitoyl-2-stearoyl-PC (PSPC), and 1-stearoyl-2-palmitoyl-PC (SPPC), with different vesicle sizes were investigated by a high-pressure fluorescence method using the polarity-sensitive fluorescent probe Prodan. The second derivative of fluorescence spectra for all the PCs of small-sized vesicle showed four minima characteristic of four membrane states on the spectra irrespective of the acyl-chain symmetry, whereas those of large-sized vesicle had one more minimum originating from the most hydrophilic site at the membrane surface. These findings indicate that Prodan molecules can distribute into multiple sites in the bilayer and move around the head-group region depending on the vesicle size. The behavior of the spectra in the SPPC bilayer suggested that the interdigitated gel phase had a less polar "pocket" formed by a space between uneven terminal methyl ends of the sn-1 and sn-2 chains. It turned out that the curvature of vesicles affects the distribution of the Prodan molecules in all phases, more particularly in the interdigitated gel phase.

Annals of the New York Academy of Sciences


Pressure Effect on the Bilayer Phase Transition of Asymmetric Lipids with an Unsaturated Acyl Chain

The bilayer phase transitions of mixed-chain lipids with monounsaturated acyl chain in the sn-2 position, 1-myristoyl-2-oleoyl-sn-glycero-3-phosphocholine (MOPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), and with a polyunsaturated acyl chain in the sn-2 position, 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine (SLPC), 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (SAPC), and 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (SDPC), were observed by differential scanning calorimetry (DSC) under ambient pressure and by light-transmittance measurements under high pressure. The DSC thermogram for each lipid bilayer showed only one transition between the lamellar gel and liquid crystalline phases. The introduction of one or two cis double bonds into the sn-2 acyl chain caused the significant depression of the main-transition temperature and an obvious decrease of enthalpy and volume changes associated with the transition. These features are attributable to loose packing of saturated and unsaturated acyl chains in the bilayer gel phase. The existence of four or six double bonds in the sn-2 chain produced no further decrease in the transition temperature, and in fact six double bonds caused a slight increase in the transition temperature. Thermodynamic properties associated with the bilayer phase transition were discussed.


Inhibition of anti-fluorescent probe monoclonal antibody by long-chain amphiphiles

Inhibitions of amphiphiles with a long chain (alcohols with carbon number of 10, 12, 14, 16 and the corresponding fatty acids) on the antigen-antibody reaction between fluorescent probe (fluorescein (FL)) and anti-fluorescent probe monoclonal antibody (immunoglobulin G (IgG)-49) were investigated by fluorescence spectroscopy. The resulting inhibition modes were compared with those of specific inhibitors, 5- and 6-aminofluoresceins (5- and 6-FLNH(2)). In the presence of all inhibitors, the fluorescence quenching of FL as the result of inhibitor binding to IgG-49 was hindered in an inhibitor concentration-dependent manner. The values of IC(50) and Hill number for the inhibitors were determined from dose-response curves of the quenching inhibition. The IC(50) values of the alcohols were much more dependent on the chain length than those of the fatty acids although all the values were in orders of microM. The Hill numbers of both kinds of inhibitors became larger values than 1, but they had different values for a series of alcohols and fatty acids, respectively. By contrast, the IC(50) values of 5- and 6-FLNH(2) were in orders of nM and the Hill numbers became smaller values than 1. Since the Lineweaver-Burk plots produced an intersection point on the intercept of the X-axis for the long-chain inhibitors with carbon number of 14 while did that on the intercept of the Y-axis for 6-FLNH(2), respectively, we judged the inhibition modes of the former as non-competitive ones and those of the latter as a competitive one. Further, the effect of pressure on the inhibition by C(14)OH, C(13)COOH and 5-FLNH(2) was examined, and the standard volume changes of IgG-49 for the inhibitor binding were calculated from the Johnson-Eyring plots. The volume change for 5-FLNH(2) was smaller than those for C(14)OH and C(13)COOH although they became all negative. This suggests that the volume of IgG-49 shrinks by the addition of these inhibitors, and IgG-49 is not relevant to a model protein for the molecular mechanism of anesthesia.


Chain asymmetry alters thermotropic and barotropic properties of phospholipid bilayer membranes

The alignment of the sn-1 and sn-2 acyl chains at the terminal methyl ends generally produces significant influence on the thermodynamic properties of the bilayer phase transitions. We investigated the bilayer phase behavior of asymmetric phospholipids, myristoylpalmitoylphosphatidylcholine and palmitoylmyristoylphosphatidylcholine, by high-pressure light-transmittance and Prodan-fluorescence techniques and differential scanning calorimetry. Constructed temperature-pressure phase diagrams revealed that no stable Lbeta' phase can exist in the whole pressure range because of the formation of the most stable Lc phase. Nevertheless, the pretransition, the detection of which is severely hampered by the exceptionally prompt formation of the Lc phase, was successfully observed. Moreover, the effect of the total and difference of the sn-1 and sn-2 acyl chain lengths on minimal interdigitation pressure (MIP) was summarized in a MIP vs. chain-length inequivalence parameter plot, where the effect was proved to be classified in three zones depending on the alignment of both terminal methyl ends.


A comparative study on specific and nonspecific interactions in bovine serum albumin: thermal and volume effects of halothane and palmitic acid


Interdigitation and vesicle-to-micelle transformation induced by a local anesthetic tetracaine in phospholipids bilayers

The phase transitions of distearoyl- (DSPC), dipalmitoyl- (DPPC) and dimyristoyl-phosphatidylcholine (DMPC) bilayer membranes were observed by means of differential scanning calorimetry as a function of the concentration of a local anesthetic tetracaine hydrochloride (TC.HCl). The depression of both temperatures of the main- and pre-transition, which is accompanied by a decrease in enthalpy changes for both transitions, was observed initially by the addition of TC.HCl. Bilayer interdigitation, which is accompanied by an increase in enthalpy change for the main transition from the interdigitated gel phase to the liquid crystalline phase, was followed by disappearance of the pretransition. The TC.HCl concentration necessary for the bilayer interdigitation was found to be 10, 21 and 6 mmol kg(-1) for DSPC, DPPC and DMPC bilayers, respectively, which was not consistent with the order of acyl-chain length of lipids. Biphasic interactions for the interdigitation, that is, repulsive interaction between polar head groups and van der Waals attractive interaction between hydrophobic chains of lipids, were discussed. On the other hand, vesicle-to-micelle transformation, which is accompanied by a cooperative decrease in enthalpy change for the main transition, was observed at higher concentration of TC.HCl and was confirmed by the vesicle size determined by the dynamic light scattering. The longer the acyl-chain length of lipids, the higher the TC.HCl concentration necessary for the vesicle-to-micelle transformation.


Effect of a Local Anesthetic Lidocaine Hydrochloride on the Bilayer Structure of Phospholipids

The effect of a local anesthetic, lidocaine hydrochloride (LC x HCl), on the bilayer systems of purified egg phosphatidylcholine (EPC), dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) was studied by means of small-angle X-ray scattering (SAXS), Prodan fluorescence and electrophoretic light scattering. In the liquid crystalline phase of EPC and DOPC bilayers, the contraction of lamellar distance by ca. 0.8-1.0 nm and the decrease of average vesicle size were observed in the presence of LC x HCl. The adsorption of LC x HCl on the vesicle interface brought about the lateral expansion of bilayers and the decrease in the radius of curvature of vesicles. The contraction in the lamellar distance of EPC bilayer caused by high concentration of LC x HCl is attributable to the chain folding in the liquid crystalline state. In the gel phase of DPPC bilayer, the contraction of the lamellar distance in the presence of 0.37 M LC x HCl amounts to 1.6 nm, and the emission maximum of Prodan fluorescence was red-shifted from 440 nm to 518 nm. These phenomena are attributed to the formation of LC x HCl-induced interdigitated gel phase.


Barotropic and thermotropic bilayer phase behavior of positional isomers of unsaturated mixed-chain phosphatidylcholines

The bilayer phase transitions of six kinds of mixed-chain phosphatidylcholines (PCs) with an unsaturated acyl chain in the sn-1 or sn-2 position, 1-oleoyl-2-stearoyl- (OSPC), 1-stearoyl-2-oleoyl- (SOPC), 1-oleoyl-2-palmitoyl- (OPPC), 1-palmitoyl-2-oleoyl- (POPC), 1-oleoyl-2-myristoyl- (OMPC) and 1-myristoyl-2-oleoyl-sn-glycero-3-phosphocholine (MOPC), were observed by means of differential scanning calorimetry (DSC) and high-pressure light transmittance measurements. Bilayer membranes of SOPC, POPC and MOPC with an unsaturated acyl chain in the sn-2 position exhibited only one phase transition, which was identified as the main transition between the lamellar gel (L(beta)) and liquid crystalline (L(alpha)) phases. On the other hand, the bilayer membranes of OSPC, OPPC and OMPC with an unsaturated acyl chain in the sn-1 position exhibited not only the main transition but also a transition from the lamellar crystal (L(c)) to the L(beta) (or L(alpha)) phase. The stability of their gel phases was markedly affected by pressure and chain length of the saturated acyl chain in the sn-2 position. Considering the effective chain lengths of unsaturated mixed-chain PCs, the difference in the effective chain length between the sn-1 and sn-2 acyl chains was proven to be closely related to the temperature difference of the main transition. That is, a mismatch of the effective chain length promotes a temperature difference of the main transition between the positional isomers. Anomalously small volume changes of the L(c)/L(alpha) transition for the OPPC and OMPC bilayers were found despite their large enthalpy changes. This behavior is attributable to the existence of a cis double bond and to significant inequivalence between the sn-1 and sn-2 acyl chains, which brings about a small volume change for chain melting due to loose chain packing, corresponding to a large partial molar volume, even in the L(c) phase. Further, the bilayer behavior of unsaturated mixed-chain PCs containing an unsaturated acyl chain in the sn-1 or sn-2 position was well explained by the chemical-potential diagram of a lipid in each phase.

Biochimica et Biophysica Acta (BBA) - Biomembranes


Interaction modes of long-chain fatty acids in dipalmitoylphosphatidylcholine bilayer membrane: contrast to mode of inhalation anesthetics

The effects of long-chain fatty acids (four saturated and two unsaturated fatty acids, one derivative) on phase transitions of dipalmitoylphosphatidylcholine (DPPC) bilayer membranes were examined in the low concentration region, and the results were compared with those for an inhalation anesthetic. The effects of all fatty acids on the pre- and main-transition temperatures of the DPPC bilayer membrane appeared in the concentration range of microM order while that of the anesthetic appeared in the mM order. The appearance modes of these ligand actions were significantly different from one another. The three differential partition coefficients of the ligands between two phases of the DPPC bilayer membrane were evaluated by applying the thermodynamic equation to the variation of the phase-transition temperatures. The DPPC bilayer membranes showed the different receptivity for the ligands; the saturated fatty acids had an affinity for gel phase whereas unsaturated fatty acids and an anesthetic had an affinity for liquid-crystalline phase to the contrary. In particular, the receptivity for the ligands in the gel phase markedly changed depending on kinds of ligands. The interaction modes between the DPPC and fatty acid molecules in the gel phase were considered from the hexagonal lattice model. The disappearance compositions of the pretransition by the fatty acids coincided with the compositions at which the membrane is all covered by the units in each of which two fatty acids molecules are regularly distributed in the hexagonal lattice in a different way, and the distribution depended on the chain length and existence of a double bond for the fatty acids. The interpretation did not hold for the case of the anesthetic at all, which proved that a number of anesthetic molecules act the surface region of the bilayer membrane nonspecifically. The present study clearly implies that DPPC bilayer membranes have high ability to recognize kinds of ligand molecules and can discriminate among them with specific interaction by the membrane states.


High-pressure study on bilayer phase behavior of oleoylmyristoyl- and myristoyloleoyl-phosphatidylcholines

We investigated the thermotropic and barotropic bilayer phase behavior of 1-myristoyl-2-oleoyl-sn-glycero-3-phosphocholine (MOPC) and 1-oleoyl-2-myristoyl-sn-glycero-3-phosphocholine (OMPC) by means of the differential scanning calorimetry (DSC) and high-pressure light-transmittance technique. Water could be used as a solvent for measurements at high pressures because of the elevation of the transition temperatures above 0 degrees C by pressurization, whereas aqueous 50 wt.% ethylene glycol solution was used mainly for those at low pressures. Only one phase transition was observed in the DSC thermogram of the MOPC bilayer membrane as an endothermic peak, and also observed at high pressures as an abrupt change of the light-transmittance. The transition was assigned as a main transition between the lamellar gel (L(beta)) and liquid-crystalline (L(alpha)) phases on the basis of the values of enthalpy change (DeltaH) and slope of the transition temperature with respect to pressure (dT/dP). The DSC thermogram of the OMPC bilayer membrane similarly showed a single endothermic peak but two kinds of phase transitions were observed at different temperatures in the light-transmittance profile at high pressures. The extrapolation of the lower-temperature transition in the high-pressure range to an ambient pressure coincided with the transition observed in the DSC thermogram. This transition was identified as a transition between the lamellar crystal (L(c)) and L(alpha) (or L(beta)) phases from the DeltaH and dT/dP values. The higher-temperature transition, appearing only at high pressures, was identified as the L(beta)/L(alpha) transition considering the topological resemblance of its temperature-pressure phase diagram as that of the dioleoylphosphatidylcholine bilayer membrane. The phase diagram of the OMPC bilayer membrane demonstrated that the L(beta) phase cannot exist at pressures below ca. 190 MPa while it can exist stably in a finite temperature range at pressures above the pressure.


Lateral phase separation in cholesterol/diheptadecanoylphosphatidylcholine binary bilayer membrane

We investigated the phase behavior of cholesterol/diheptadecanoylphosphatidylcholine (C17:0-PC) binary bilayer membrane as a function of the cholesterol composition (X(ch)) by fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and differential scanning calorimetry (DSC). The fluorescence spectra showed that the wavelength at the maximum intensity (lambda(max)) changed depending on the bilayer state: ca. 440 nm for the lamellar gel (L'(beta) or L(beta)) and the liquid ordered (L(o)) phases and ca. 490 nm for the liquid-crystalline (L(alpha)) phase. The transition temperatures were determined from the temperature dependence of lambda(max) and endothermic peaks of the DSC thermograms. Both measurements showed that the pre- and main transition disappear around X(ch)=0.05 and 0.30, respectively. The constructed temperature-X(ch) phase diagram resembled a typical phase diagram for a eutectic binary mixture containing a peritectic point. The presence of a peritectic point at X(ch)=0.15 suggested that a complex of cholesterol and C17:0-PC is stoichiometrically formed in the gel phase. Consideration based on the hexagonal lattice model revealed that the compositions of 0.05 and 0.15 correspond to the bilayer states where cholesterol molecules are regularly distributed in different ways. The former is nearly equal to the composition for the membrane occupied entirely with Units (1:18), composed of a cholesterol and 18 surrounding C17:0-PC molecules within the next-next nearest neighbor sites. The latter is represented by a Unit (1:6), including a cholesterol and 6 surrounding C17:0-PC molecules. Further, the disappearance of the main transition at X(ch)=0.30 indicates that the pure L(o) phase can exist in X(ch)>0.30. The eutectic behavior observed in the phase diagram was explainable in terms of phase separation between two different types of regions with different types of regular distributions of cholesterol.


エーテル結合型リン脂質における指組み構造形成

エーテル結合型リン脂質における指組み構造形成

High Pressure Bioscience and Biotechnology

高圧バイオサイエンスとバイオテクノロジー


高圧力下におけるジノナデカノイルホスファチジルコリン二分子膜の相挙動

高圧力下におけるジノナデカノイルホスファチジルコリン二分子膜の相挙動

高圧バイオサイエンスとバイオテクノロジー


Thermodynamic Consideration for Nonbilayer Formation of Phospholipid Membranes

リン脂質膜の非二分子膜形成に対する熱力学的考察

高圧バイオサイエンスとバイオテクノロジー


A new interpretation of eutectic behavior for distearoylphosphatidylcholine-cholesterol binary bilayer membrane

We investigated the thermotropic phase behavior of the distearoylphosphatidylcholine (DSPC)-cholesterol binary bilayer membrane as a function of the cholesterol composition (X(ch)) by fluorescence spectroscopy using 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and differential scanning calorimetry (DSC). The fluorescence spectra, each of which has a single maximum, showed that the wavelength at the maximum intensity (lambda(max)) changed depending on the bilayer state: ca. 440 nm for the lamellar gel (L(beta)' or L(beta)) and the liquid ordered (L(o)) phases, ca. 470 nm for the ripple gel (P(beta)') phase and ca. 490 nm for the liquid crystalline (L(alpha)) phase, respectively. The transition temperatures were determined from the temperature dependences of the lambda(max) and endothermic peaks of the DSC thermograms. Both measurements showed that the pretransition disappears around X(ch)=0.035. The constructed temperature-X(ch) phase diagram indicated that the phase behavior of the binary bilayer membrane at X(ch)< or =0.15 is similar to that of general liquid-solid equilibrium for a binary system where both components are completely miscible in the liquid phase and completely immiscible in the solid phase. It was also revealed that the diagram has two characteristic points: a congruent melting point at X(ch)=0.08 and a peritectic-like point at X(ch)=0.15. The hexagonal lattice model was used for the interpretation of the phase behavior of the binary bilayer membrane. These characteristic compositions well correspond to the bilayer states in each of which cholesterol molecules are regularly distributed in the hexagonal lattice in a different way. That is, each composition of 0.035, 0.08 and 0.15 is nearly equal to that for the binary bilayer membrane which is entirely occupied with units, each composed of a cholesterol and 30 surrounding DSPC molecules within the next-next-next nearest neighbor sites (Unit (1:30): L(beta)(1:30)), with units, each of a cholesterol and 12 surrounding DSPC molecules within the next nearest sites (Unit (1:12): L(beta)(1:12)) or with units, each of a cholesterol and 6 surrounding DSPC molecules at the nearest neighbor sites (Unit (1:6): L(beta)(1:6)), respectively. Therefore, the eutectic behavior observed in the phase diagram was fully explainable in terms of a kind of phase separation between two different types of regions with different types of regular distributions of cholesterol. Further, the L(o) phase was found in the higher X(ch)-region (X(ch)>0.15). No endothermic peak over the temperature range from 10 to 80 degrees C at X(ch)=0.50 suggested that the single L(o) phase can exist at X(ch)>0.50.


Thermotropic and barotropic phase transitions of dilauroylphosphatidylcholine bilayer

The bilayer phase transitions of dilauroylphosphatidylcholine (DLPC), containing two linear acyl chains with 12 carbon atoms, were observed by means of differential scanning calorimetry (DSC) under ambient pressure and light transmittance under high pressure. When the heating scan for the DLPC bilayer in 50 wt.% aqueous ethylene glycol (EG) solution began at -30 degrees C after cold storage, the DSC thermogram showed two endothermic peaks at 1.7 and 4.5 degrees C, which correspond to the transition from the lamellar crystalline (Lc) phase to the intermediate liquid crystalline (Lx) phase and the transition from the Lx phase to the liquid crystalline (L) phase, respectively. Extremely large enthalpy change (32.9 kJ mol(-1)) is characteristic of the Lc/Lx phase transition. The DSC thermogram for the heating scan beginning from -10 degrees C showed a single endothermic peak with 9.2 kJ mol(-1) at -0.4 degrees C, which was assigned as the so-called main transition between the metastable ripple gel (P'(beta)) and metastable Lalpha phases. The DLPC bilayer under high pressure underwent three kinds of transitions in EG solution, whereas only one transition was observed in water under high pressure. The middle-temperature transition in EG solution could be assigned to the main transition because of its consistency with the main transition in water. The lower-temperature transition is probably assigned as transition from the Lc phase to the P'(beta) phase. Since the slope (dT/dp) of the Lc/P'(beta) phase boundary is smaller than that for the main transition, the Lc/P'(beta) phase boundary and the main transition curves crossed each other at 40 MPa on the temperature-pressure phase diagram. The higher-temperature transition in EG solution refers to the transition from the Lx phase to the Lalpha phase. The Lx phase disappeared at about 180 MPa, and the direct transition from the P'(beta) phase to the Lalpha phase was observed at high pressures above 180 MPa.


Cholesterol Suppresses Pressure-induced Interdigitation of Dipalmitoylphosphatidylcholine Bilayer Membrane


Effect of hydrostatic pressure on the bilayer phase behavior of symmetric and asymmetric phospholipids with the same total chain length

The bilayer phase transitions of palmitoylstearoyl-phosphatidylcholine (PSPC), diheptadecanoyl-PC (C17PC) and stearoylpalmitoyl-PC (SPPC) which have the same total carbon numbers in the two acyl chains were observed by differential scanning calorimetry and high-pressure optical method. As the temperature increased, these bilayers exhibited four phases of the subgel (Lc), lamellar gel (L beta'), ripple gel (P beta') and liquid crystal (L alpha), in turn. The Lc phase was observed only in the first heating scan after cold storage. The temperatures of the phase transitions were almost linearly elevated by applying pressure. The temperature-pressure phase diagrams and the thermodynamic quantities associated with the phase transitions were compared among the lipid bilayers. For all the bilayers studied, the pressure-induced interdigitated gel (L beta I) phase appeared above the critical interdigitation pressure (CIP) between the L beta' and P beta' phases. The CIPs for the PSPC, C17PC and SPPC bilayers were found to be 50.6, 79.1 and 93.0 MPa, respectively. Contribution of two acyl chains to thermodynamic properties for the phase transitions of asymmetric PSPC and SPPC bilayers was not even. The sn-2 acyl chain lengths of asymmetric PCs governed primarily the bilayer properties. The fluorescence spectra of Prodan in lipid bilayers showed the emission maxima characteristic of bilayer phases, which were dependent on the location of Prodan in the bilayers. Second derivative of fluorescent spectrum exhibited the original emission spectrum of Prodan to be composed of the distribution of Prodan into multiple locations in the lipid bilayer. The F''497/F''430 value, a ratio of second derivative of fluorescence intensity at 497 nm to that at 430 nm, is decisive evidence whether bilayer interdigitation will occur. With respect to the L beta'/L beta I phase transition in the SPPC bilayer, the emission maximum of Prodan exhibited the narrow-range red-shift from 441 to 449 nm, indicating that the L beta I phase in the SPPC bilayer has a less polar "pocket" formed by a space between uneven terminal methyl ends of the sn-1 and sn-2 chains, in which the Prodan molecule remains stably.


Miscibility and interaction between 1-alkanol and short-chain phosphocholine in the adsorbed film and micelles

The miscibility and interaction of 1-hexanol (C6OH) and 1-heptanol (C7OH) with 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) in the adsorbed films and micelles were investigated by measuring the surface tension of aqueous C6OH-DHPC and aqueous C7OH-DHPC solutions. The surface density, the mean molecular area, the composition of the adsorbed film, and the excess Gibbs energy of adsorption g(H,E), were estimated. Further, the critical micelle concentration of the mixtures was determined from the surface tension versus molality curves; the micellar composition was calculated. The miscibility of the 1-alkanols and DHPC molecules in the adsorbed film and micelles was examined using the phase diagram of adsorption (PDA) and that of micellization (PDM). The PDA and the composition dependence of g(H,E) indicated the non-ideal mixing of the 1-alkanols and DHPC molecules due to the attractive interaction between the molecules in the adsorbed film, while the PDM indicated that the 1-alkanol molecules were not incorporated in the micelles within DHPC rich region. The dependence of the mean molecular area of the mixtures on the surface composition suggested that the packing property of the adsorbed film depends on the chain length of 1-alkanol: C6OH expands the DHPC adsorbed film more than C7OH.


Volume study on the exclusion of lithium naphthylsulfonate from lithium decylsulfonate micelles


Thermotropic and barotropic phase transitions in bilayer membranes of ether-linked phospholipids with varying alkyl chain lengths

疎水鎖長の異なる一連のエーテル型リン脂質ジアルキルホスファチジルコリン二分子膜の相転移に関する熱力学諸量と温度-圧力相図を対応するエステル型リン脂質の結果と比較した．主転移に関する熱力学量の詳細な比較から，ゲル相中におけるエーテル型リン脂質の相互作用はエステル型リン脂質よりも弱いことを示した．さらにエーテル型リン脂質の相図はエステル型リン脂質の相図の高温，高圧領域に対応することを明らかにした．

Biochimica et Biophysica Acta (BBA) - Biomembranes


Adsorption-Equilibrium Surface Tension of Surfactant Solutions -Examination by the Drop Volume Method-

Bulletin of the Chemical Society of Japan


Bilayer Phase Transitions of N-methylated Dioleoylphosphatidylethanolamines under High Pressure

The bilayer phase transitions of four kinds of unsaturated phospholipids with different-sized polar head groups, dioleoylphosphatidylethanolamine (DOPE), dioleoylphosphatidyl-N-methylethanolamine (DOMePE), dioleoylphosphatidyl-N,N-dimethylethanolamine (DOMe2PE) and dioleoylphosphatidylcholine (DOPC), were observed by means of differential scanning calorimetry (DSC) and high-pressure light-transmittance. DSC thermogram and light-transmittance curve for each phospholipid vesicle solution exhibited only one phase transition under ambient pressure, respectively. The light-transmittance of DOPC solution at pressure higher than 234 MPa abruptly increased stepwise at two temperatures, which corresponds to the appearance of stable subgel and lamellar gel phases under high pressure in addition to the liquid crystal phase. The constructed temperature (T)-pressure (p) phase diagrams were compared among these phospholipids. The phase-transition temperatures of the phospholipids decreased stepwise by N-methylation of the head group. The slops of the T-p phase boundary (dT/dp) of DOPE, DOMePE and DOMe2PE bilayers (0.127-0.145 K MPa-1) were found to be close to that of the transition from the lamellar crystal (or subgel; Lc) phase to the liquid crystal (Lalpha) phase for DOPC bilayer (0.131 K MPa-1). On the other hand, the dT/dp value of the main transition from the lamellar gel (Lbeta) phase to the Lalpha phase for DOPC bilayer (0.233 K MPa-1) was significantly different from that of the Lc/Lalpha transition, hence both curves intersected with each other at 234 MPa. The thermodynamic quantities associated with the phase transition of DOPE, DOMePE and DOMe2PE bilayers had also similar values to those for the Lc/Lalpha transition of DOPC bilayer. Taking into account of the values of transition temperature, dT/dp and thermodynamic quantities compared with the corresponding results of saturated phospholipids, we identified the phase transitions observed in the DOPE, DOMePE and DOMe2PE bilayers as the transition from the Lc phase to the Lalpha phase although they have been regarded as the main transition in the previous studies. The Lbeta phase is probably unstable for DOPE, DOMePE and DOMe2PE bilayers at all pressures, it exists as a metastable phase at pressures below 234 MPa while as a stable phase at pressures above 234 MPa in DOPC bilayer. The difference in phase stability among the phospholipid bilayers is originated from that in hydration structure of the polar head groups.


Barotropic phase transition between the lamellar liquid crystal phase and the inverted hexagonal phase of dioleoylphosphatidylethanolamine

The phase transition between the lamellar liquid crystal (Lalpha) phase and the inverted hexagonal (H(II)) phase of dioleoylphosphatidylethanolamine (DOPE) in aqueous NaCl solutions was observed by means of differential scanning calorimetry (DSC) under ambient pressure and light-transmittance technique under high pressure. The pressure dependence of the transition temperature (dT/dp) and the thermodynamic quantities for the Lalpha/H(II) transition were compared with those of another phase transition found in the DOPE bilayer membrane, which is the transition from the lamellar crystal (Lc) phase to the Lalpha phase. The dT/dp value of the Lalpha/H(II) transition was about 3.5 times as large as that of the Lc/Lalpha transition while the thermodynamic quantities were significantly smaller than those of the latter to the contrary. Comparing the enthalpy and volume behavior of the Lalpha/H(II) transition with that of the Lc/Lalpha transition, we concluded that the Lalpha/H(II) transition can be regarded as the volume-controlled transition for the reconstruction of molecular packing.


Pressure-Induced Phase Transitions of Lipid Bilayers Observed by Fluorescent Probes Prodan and Laurdan

ジステアロイルホスファチジルコリン二重膜中における2種類の蛍光プローブ色素プロダンとローダンの蛍光スペクトルを温度一定下，圧力の関数として観測した．二重膜の相状態に対応して両プローブの蛍光スペクトル極大波長の変化を見出し，各相状態における両プローブ分子の配向位置を推定した．ゲル相から液晶相への主転移においては，両プローブ共に極大波長に鋭敏な変化が観測されたが，指組み構造相への転移に関してはプロダンの極大波長に変化が見られたが，ローダンの極大波長には変化が見られなかった．ローダン分子はプロダン分子とは異なり，その長いアシル鎖のために二重膜の疎水性中心にアンカーとして固定され，指組み構造形成の際に脂質分子のグリセロール骨格から排除されないことが示唆された．


Observation of the lipid bilayer phase transition using the ion sensor

イオン選択電極法による脂質二分子膜の相転移観測

Some aromatic amine local anesthetics are a kind of amphiphilic ion. Binding of local anesthetics, dibucaine (DC), bupivacaine (BC), and lidocaine (LC) to a dipalmitoylphosphatidylcholine (DPPC) bilayer membrane was studied by potentiometry with ion-selective electrodes sensitive to DC, BC and LC cations, respectively. The DPPC membrane-buffer partition coefficient was directly determined as a function of the anesthetic concentration and the temperature. The DPPC bilayer underwent a thermotropic pretransition from the lamellar gel phase to the ripple gel phase as well as a main transition from the ripple gel phase to the liquid crystal phase. The partition coefficients of anesthetics at pH 5.5 varied with the temperature, namely the bilayer phases. Potentiometry using an ion-selective electrode sensitive to amphiphilic ions is effective for the detection of a bilayer phase transition through partition coefficients.


Effect of deuterium oxide on the thermodynamic quantities associated with phase transitions of phosphatidylcholine bilayer membranes

重水および軽水中における3種類のホスファチジルコリン(ジパルミトイル，ジステアロイル，ジヘキサデシル)二分子膜の相転移を示差走査熱量測定および高圧光透過率測定で追跡した．重水置換の効果は主転移よりも前転移を含むゲル相間転移に大きく現れ，指組み構造形成を不安定化した．両溶媒中における二分子膜の界面自由エネルギーの相違を考察し，重水置換は二分子膜界面において分子占有面積の縮小を引き起こし，より小さな分子占有面積を有する膜状態がその影響を顕著に受けることを明らかにした．


Effect of Pressure on the Prodan Fluorescence in Bilayer Membranes of Phospholipids with Varying Acyl Chain Lengths

4種類のアシル鎖長が異なるホスファチジルコリン(ジラウロイル，ジミリストイル，ジパルミトイル，ジステアロイル)二分子膜中における蛍光プローブ色素プロダンの蛍光スペクトルを圧力の関数として観測した．二分子膜の相状態に対応して蛍光スペクトル極大波長の変化を見出し，各相状態におけるプロダン分子の配向位置を推定した．リップルゲル相におけるプロダンの蛍光強度にはアシル鎖長および圧力依存性を観測した．ゲル相および液晶相の極大波長における蛍光強度比は相転移に伴い鋭敏に変化し，特に指組み構造ゲル相形成の検出に役立つことを示した．


Effect of cholesterol on partition coefficients of local anesthetic into bilayer membranes of dimyristoylphosphatidylcholine

脂質二分子膜への局所麻酔薬の分配に及ぼすコレステロールの影響

リン脂質二分子膜への局所麻酔薬の分配に対するコレステロールの影響を調べるためにコレステロール濃度の異なるジミリストイルホスファチジルコリン-コレステロール混合二分子膜へのジブカイン塩酸塩の取り込みを局所麻酔薬選択性電極法により調べた．コレステロール低組成領域では，ゲル相における分配係数は増加し，液晶相の分配係数は減少する二相性を観測した．他方，コレステロール高組成領域では分配係数は相状態によらず一定値となり，コレステロール濃度の増加に伴って減少した．上記の結果はコレステロールは麻酔薬の分配に対して制御能を有することを示唆する．


Partition coefficients of local anesthetic into lipid bilayer membranes containing unsaturated Acyl chain

不飽和アシル鎖を持つリン脂質二分子膜への局所麻酔薬の分配

リン脂質アシル鎖の飽和および不飽和形式が麻酔薬の生体膜への分配に与える影響を調べる目的で，4種類の不飽和ホスファチジルコリン(1-オレオイル-2-ステアロイル，1-ステアロイル-2-オレオイル，ジオレオイル，ジエライドイル)二分子膜へのジブカイン塩酸塩の取り込みを局所麻酔薬選択性電極法により調べた．算出された分配係数の値はジエライドイル<1-オレオイル-2-ステアロイル≒1-ステアロイル-2-オレオイル<ジオレオイルの順序で大きくなり，脂質膜への結合は脂質分子のアシル鎖構造にも依存することを示した．


Effect of halothane on the viscosity of aqueous bovine serum albumin solutions

牛血清アルブミン水溶液の粘度におよぼすハロセンの影響

溶液粘度の迅速，高精度且つ自動測定を目的として，オストワルド粘度計を使用した自動粘度測定装置を開発し，牛血清アルブミン水溶液の粘度測定を行った．中性pH領域において吸入麻酔薬ハロセン存在下における牛血清アルブミン水溶液の固有粘度は非存在下のものよりも小さな値となり，ハロセン添加により溶液内で牛血清アルブミンの体積が収縮することが示唆された．上記の結果より，非常に親水性の強いタンパク質は麻酔作用のモデルタンパク質としては適当ではないと推察した．


Inhibition modes of amphiphilic ligands with a long chain on the anti-fluorescent probe monoclonal antibody

蛍光プローブ特異的モノクローナル抗体への長鎖両親媒性リガンドの阻害様式

蛍光プローブフルオレセインとその特異的モノクローナル抗体との抗原抗体反応におよぼす長鎖両親媒性リガンド(炭素数10，12，14，16のアルコールおよび対応する脂肪酸)の作用様式を蛍光分光法で調べた．消光阻害の用量応答曲線はアルコール系列および脂肪酸系列でそれぞれ異なり，両リガンドの阻害様式の違いが示唆された．また，上記リガンドの阻害反応に対する圧力効果を調べ，両リガンド存在下ではフルオレセイン特異的モノクローナル抗体の体積は収縮することがわかった．


Thermotropic and barotropic phase transitions of N-methylated dipalmitoylphosphatidylethanolamine bilayers

極性基の大きさの異なる4種類のN-メチル化ジパルミトイルホスファチジルエタノールアミン二分子膜の相転移を高圧光透過法で観測した．ゲル相から液晶相への主転移および結晶相からゲル相への副転移，両転移温度は共に加圧により上昇し，極性基サイズの増大につれて降下した．ジパルミトイルホスファチジルエタノールアミン二分子膜の場合には21.8 MPaにおいて主転移温度曲線と副転移温度曲線が交差し，ゲル相は21.8 MPa以下の圧力では準安定相として存在し，21.8 MPa以上の圧力においてのみ安定相として存在することがわかった．指組み構造ゲル相に代表されるゲル相の多形現象はジパルミトイルホスファチジルコリン二分子膜のみに見出された．

Biochimica et Biophysica Acta (BBA) - Biomembranes


Dissociation Equilibrium between Uncharged and Charged Local Anesthetic Lidocaine in a Surface-Adsorbed Film

表面吸着膜中における非解離型—解離型局所麻酔薬の分配平衡を記述する熱力学関係式を導出し，非解離型局所麻酔薬リドカイン-塩酸混合水溶液の表面張力およびpHデータに適用した．計算結果の両者の表面密度から，両者の共存組成においては非解離型麻酔薬が解離型麻酔薬よりも多く存在し，吸着膜中における両者の分配挙動は3つの組成領域で特徴づけられることを示した．非解離型麻酔薬は解離型麻酔薬よりも細胞膜が提供する疎水性環境へ移行し易いことを結論づけた．


Barotropic Phase Transitions of 1-Palmitoyl-2-stearoylphosphatidylcholine Bilayer Membrane

非対称型リン脂質1-パルミトイル-2-ステアロイルホスファチジルコリン二分子膜の圧力誘起相転移を高圧光透過率測定および示差走査熱量測定により観測した．決定した相転移点に基づいて温度—圧力相図を構築し，3種類の対称型ホスファチジルコリン二分子膜の相図と比較した．1-パルミトイル-2-ステアロイルホスファチジルコリン二分子膜の相挙動は対称型ホスファチジルコリン二分子膜とは大きく異なり，指組み構造形成の臨界圧力は全ての脂質のうちで最も小さくなった．


Biological and physicochemical properties of gemini quaternary ammonium compounds in which the positions of a cross-linking sulfur in the spacer differ

Gemini型第四アンモニウム化合物(gemini QAC)の架橋構造のスルフィド結合の位置に着目した．メチレンスルフィド，エチレンジスルフィド，スルフィドがピリジン環に連結したgemini QACの3種のを合成し，抗菌活性，ヒト赤血球溶血毒性，界面活性能に関するスルフィド結合位置の影響について検討した．ピリジン環に連結したスルフィド結合を有する化合物は，抗菌力，溶血毒性，界面活性能いずれにおいても，他の2種薬剤よりも高いことが分かった．その強い抗菌力と溶血毒性は，スルフィド結合の共鳴効果によるアンモニウムカチオン電子密度の上昇，スルフィドがテトラメチレンスペーサ鎖両末端に存在することによるスペーサ鎖の高い伸縮性に起因した小さい分子占有面積，そして高い薬剤分子疎水性に寄与すると考え，スペーサ鎖の立体構造に影響し，スルフィドの位置がアンモニウムカチオン電子密度に影響を及ぼすと結論した．


Preferential partitioning of uncharged local anesthetics into the surface-adsorbed film

非解離型および解離型局所麻酔薬の競合表面吸着を調べるために3つの塩酸—非解離型局所麻酔薬(メピバカイン，ブピバカイン，ジブカイン)混合水溶液の表面張力とpHを全溶質濃度と麻酔薬組成の関数として測定した．非解離型および解離型麻酔薬の表面吸着膜中への分配量を熱力学的に計算した個々の表面密度で評価した．両者の共存領域では非解離型麻酔薬の優先的吸着が観測され，吸着膜への移行のし易さは麻酔薬分子疎水性に比例し，麻酔ポテンシーと相関した．本研究は生理的pHにおける表面活性分子は非解離型麻酔薬であることを明示した．


Anesthetic receptivity of lipid membranes with different bilayer phases

リン脂質二分子膜 の相状態と麻酔薬感受性

リン脂質二分子膜の相状態が局所麻酔薬の二分子膜中への分配に与える影響を調べるためにエステル結合型リン脂質ジパルミトイルホスファチジルコリンおよびエーテル結合型リン脂質ジヘキサデシルホスファチジルコリン二分子膜中へのジブカイン塩酸塩の取り込みを局所麻酔薬選択性電極法により調査した．決定された両二分子膜各相へのジブカインの分配係数値から，両二分子膜ともリップルゲル相および液晶相での分配係数は，ほぼ同等の値を示したが，ゲル相間ではラメラゲル相 < リップルゲル相 < 指組み構造ゲル相の順序となり差異が見られた．この差異は脂質分子の極性基当たりの占有面積とよい相関を示した．


Recognition for long-chian fatty acids by dipalmitoylphosphatidylcholine bilayer membranes

ジパルミトイルホスファチジルコリン二分子膜の長鎖脂肪酸認識

リン脂質ジパルミトイルホスファチジルコリン二分子膜相転移におよぼす4種類の長鎖脂肪酸(パルミチン酸，パルミトレイン酸，ステアリン酸，オレイン酸)と脂肪酸化合物(オレアミド)の影響を示差走査熱量法で調べた．熱力学的解析から得られた分配係数差と主転移エンタルピーから，飽和脂肪酸は脂質二分子膜ゲル相に強い親和性を有し，不飽和脂肪酸およびオレアミドは液晶相に強い親和性を有することがわかった．脂質二分子膜は高いリガンド感受性を有し，長鎖脂肪酸の鎖長や不飽和結合の有無を認識可能である．


Partition coefficients of the local anesthetic dibucaine into a lipid bilayer membrane determined with a dibucaine cation sensor

局所麻酔薬ジブカインカチオンセンサーを用いる脂質二分子膜へのジブカインの分配測定

レシチンベシクル膜中への局所麻酔薬ジブカインの分配をジブカインカチオン選択性電極を用いて調べ，その分配係数を決定した．分配係数はpH増加に伴い増大する傾向を示した．分配係数のpH依存性の解析から麻酔薬の解離型および非解離型それぞれの分配係数への分割を行い，レシチンベシクル膜中への非解離型麻酔薬の大きな分配を明確にした．生体膜中における麻酔薬分配計測への局所麻酔薬電極の有用性を示した．


Effect of Equimolar Salt to Decyltrimethylammonium Decyl Sulfate on Vesicle Formation and Surface Adsorption

デシル硫酸ナトリウムと臭化デシルトリメチルアンモニウムの1:1混合物水溶液の表面張力を温度および濃度の関数として測定した．表面張力データの解析から得られた会合体形成の熱力学量をデシル硫酸デシルトリメチルアンモニウムのものと比較した．前者の飽和吸着量は後者よりも小さくなり，またベシクル形成濃度は前者の方が大きくなった．これらの挙動は会合体形成における陽イオンと陰イオンの極性基間に働く静電的引力が対イオンの存在によって弱められたものと考えられる．両系の表面吸着量とベシクル形成のエントロピーには小さいが明白な相違が観測された．

Journal of Colloid and Interface Science


Effect of myristic acid on the phase transition temperatures of dipalmitoylphosphatidylcholine bilayer membranes

ジパルミトイルホスファチジルコリン二分子膜の相転移温度におよぼすミリスチン酸の影響

リン脂質ジパルミトイルホスファチジルコリン二分子膜相転移におよぼす長鎖脂肪酸ミリスチン酸の影響を光透過法および示差走査熱量法を用いて調べ，結果を吸入麻酔薬イソフルランのものと比較した．相転移温度変化に熱力学関係式を適用し，脂質二分子膜における両リガンドの3種類の2相間分配係数差を計算した．ミリスチン酸は脂質二分子膜の流動性を下げ，ゲル相を安定化させるが，イソフルランは逆に二分子膜の流動性を上げ，ゲル相を不安定化させることを結論づけた．


局所麻酔薬によるリン脂質二分子膜 の相転移温度降下 -リン脂質極性基の効果-

局所麻酔薬によるリン脂質二分子膜 の相転移温度降下 -リン脂質極性基の効果-

ジパルミトイルホスファチジルコリンとジミリストイルホスファチジルエタノールアミン二分子膜の相転移温度におよぼす3種類の局所麻酔薬塩酸塩(テトラカイン，リドカインおよびプロカイン)の影響を示差走査熱量測定法と光透過法を用いて調べた．麻酔薬添加による相転移温度降下度から計算したホスファチジルエタノールアミン二分子膜に対する分配係数はホスファチジルコリン二分子膜のものより小さくなった．この麻酔薬分配の相違はホスファチジルエタノールアミン二分子膜中における極性基間の強い引力的相互作用に起因している．


非解離型および解離型局所麻酔薬の競合表面吸着

非解離型および解離型局所麻酔薬の競合表面吸着

3種類の非解離型局所麻酔薬(メピバカイン，ブピバカイン，ジブカイン)を塩酸でプロトン付加させ，それら麻酔薬の非解離型および解離型両者の競合表面吸着を非解離型麻酔薬-塩酸混合水溶液の表面張力とpH測定から調べた．混合組成が0.5以上の場合においてのみ両者が水溶液中で共存し，この組成領域では，非解離型麻酔薬の方が解離型麻酔薬より優先的に表面吸着膜へ移行した．また，表面吸着膜への移行のし易さは麻酔薬分子の有する疎水性に比例し，麻酔ポテンシーと相関していることがわかった．


Partition coefficients of charged and uncharged local anesthetics into dipalmitoylphosphatidylcholine bilayer membrane: estimation from pH dependence on the depression of phase transition temperatures

Effects of the local anesthetics, dibucaine, bupivacaine and lidocaine on the phase transition temperatures of dipalmitoylphosphatidylcholine (DPPC) bilayer membrane were studied by the optical method. We focus our attention on pH dependence of the depression of main transition and pretransition temperatures. The temperatures of both transitions of DPPC bilayer membrane were depressed by the addition of anesthetics; the higher the value of pH, the larger the depression of main transition temperature and/or pretransition temperature by anesthetics. By extending the colligative thermodynamic framework to the depression of main transition temperature by an anesthetic, we can estimate the differential partition coefficient, which is defined by the difference in partition coefficients of an anesthetic into the ripple gel and liquid crystal phases. The difference in partition coefficient between the lamellar and ripple gel phases can also be estimated from the depression of pretransition temperature. Since the differential partition coefficients include both contributions of the charged and uncharged anesthetics, we could estimate the partition coefficients of the charged and uncharged anesthetic into the membranes from the pH dependence of differential partition coefficients. The liquid crystalline membrane of DPPC bilayer was more receptive to the uncharged local anesthetics than the charged species. The partition coefficients of the charged and uncharged anesthetics into the liquid crystalline phase of DPPC bilayer membrane were 3540 and 249000 (for dibucaine), 1120 and 83900 (for bupivacaine), 256 and 11700 (for lidocaine), respectively. The transfer free energy of uncharged anesthetics from the aqueous phase to the liquid crystalline membrane was well correlated to the local anesthetic potency.

リン脂質ジパルミトイルホスファチジルコリン二分子膜の相転移温度におよぼす3種類の局所麻酔薬(ジブカイン，ブピバカイン，リドカイン)の影響を光学的手法で追跡した．脂質二分子膜の主転移および前転移温度は麻酔薬添加により降下し，pH増加につれて降下度は大きくなった．束一性の熱力学関係式より各局所麻酔薬の二相間分配係数を計算し，さらに分配係数のpH依存性から解離型および非解離型麻酔薬それぞれの分配係数を見積もった．脂質二分子膜は非解離型麻酔薬に強い感受性を示し，麻酔薬の取り込まれ易さは麻酔ポテンシーによく相関した．


Partitioning of uncharged local anesthetic benzocaine into model biomembranes

The partitioning of uncharged local anesthetic benzocaine (BzC) into molecular aggregates formed by cationic surfactant decylammonium chloride (DeAC) and phospholipid dipalmitoylphosphatidylcholine (DPPC) was studied from the surface tension and light transmittance measurements. The quantities concerning the partitioning of BzC, the compositions of BzC in the surface-adsorbed film and micelle and three kinds of differential partition coefficients corresponding to phase transitions of the DPPC bilayer membrane were evaluated from thermodynamic analysis of the experimental data. The surface-adsorbed film and micelle were more abundant in BzC than the aqueous solution and significantly large differential partition coefficients for the DPPC membranes were observed. The results clearly showed that the BzC molecules greatly partitioned into hydrophobic environments produced by surfactant-monolayer and phospholipid-bilayer membranes. The partitioning behavior of BzC was also compared with that of charged local anesthetic procaine hydrochloride (PC.HCl). It was shown that the PC.HCl molecule did not or hardly partition into such hydrophobic environments. The contrasting results of the partitioning between BzC and PC.HCl are attributable to the drastic decrease of hydrophilicity of BzC due to the lacking of ionic polar head group in comparison with PC.HCl.

陽イオン性界面活性剤塩化デシルアンモニウムとリン脂質ジパルミトイルホスファチジルコリンが形成する分子集合体中への非解離型局所麻酔薬ベンゾカインの分配を表面張力および光透過率測定から調べた．表面吸着膜とミセルは水溶液中に比べてベンゾカインに富み，脂質二分子膜に対する非常に大きな分配係数が得られた．上記ベンゾカインの分配挙動を構造が類似した解離型局所麻酔薬プロカイン塩酸塩のものと比較し，両者の分配差はイオン性極性基の有無による親水性の変化に起因することを示した．


Volumetric Study on the Protein-Anesthetic Binding

Thermodynamic equations describing the volume behavior of protein-ligand mixtures in water were derived. In order to estimate the volume and binding parameters, the equations were combined with a Langmuir-type binding isotherm. Densities of aqueous solutions of mixtures of bovine serum albumin (BSA) and octanol (C8OH) were measured as a function of total BSA molality, m(M)(T), at constant total C8OH molalities, m(X)(T). The data were analyzed by the equations. The partial molar volumes at infinite dilution of BSA and C8OH, V(M)(T,0) and V(X)(T,0), respectively, were estimated. It was seen that V(M)(T,0) decreases by the addition of C8OH to the solution and that V(X)(T,0) decreases gradually with increasing m(M)(T) and approaches asymptotically to a certain value at high m(M)(T). From the concentration dependence of V(M)(T,0) and V(X)(T,0), the values of the association constant K=392 kg mol(-1), the maximum binding number b(max)=1.9, and the volume change DeltaV=-109 cm(3) mol(-1) were obtained for BSA-C8OH interaction in water. The negative value of DeltaV indicates that the hydrophobic interaction reduces the protein volume and elevation of pressure promotes BSA-C8OH binding. These results is inconsistent with the pressure reversal of anesthesia.

水中におけるタンパク質-リガンドの体積挙動を記述する熱力学関係式を導出した．牛血清アルブミンとオクタノールの混合水溶液の密度を測定し，導出した式を用いて解析した．オクタノール結合による牛血清アルブミンの体積変化に対して大きな負の値が得られた．負の体積変化は疎水相互作用がタンパク質の体積を減少させ，加圧は両者の結合を促進することを意味する．この結果は麻酔作用の圧力拮抗現象と矛盾することから牛血清アルブミンは麻酔作用のモデルタンパク質としては相応しくないと結論した．


Solubilization Study of Local Anesthetics into Sodium Dodecyl Sulfate Micelle Using Anesthetic Cation Selective Electrodes

The free concentrations of local anesthetic cations in equilibrium with sodium dodecyl sulfate (SDS) micelle which solubilized the anesthetic were determined by using ion-selective electrodes sensitive to local anesthetics, procaine (PC), lidocaine (LC), and mepivacaine (MC). Solubilizate distribution between water and SDS micelle was analyzed by means of the stepwise mass-action model. Association constant, K(1), was found to depend upon the anesthetic concentration, which decreased exponentially as the concentration of free anesthetic increased. Therefore, K(1) should include the interaction function φ(A) as K(1)=K(int)exp{-φ(A)} where K(int) is an intrinsic association constant. φ(A) is an increasing function of the anesthetic concentration, which means that occupation of a solubilization site by a local anesthetic cation makes sequential solubilization more difficult. The binding affinity of an anesthetic with SDS micelle increased in the following order PC<LC<MC.The critical micelle concentration (CMC) of mixed micelle was determined as a function of the concentration of free anesthetic. The CMC decreased with an increasing amount of anesthetics solubilized. All the anesthetic compositions in the micelle calculated thermodynamically from the CMC data were larger than the corresponding ones in the aqueous phase. Although the local anesthetics used here do not form micelles by themselves, the CMC vs composition curve can be regarded as a part of a micellar phase diagram showing the negative azeotropic behavior, which reflects the attractive interaction between the anionic surfactant micelle and the local anesthetic cation.

ドデシル硫酸ナトリウムミセルに可溶化した3種類の局所麻酔薬(プロカイン，リドカイン，メピバカイン)と水溶液中に平衡に存在するそれぞれの遊離局所麻酔薬カチオン濃度を局所麻酔薬選択性電極を用いて決定した．水中とミセル中の可溶化物質の分布を段階的質量作用モデルを用いて解析した．ミセルとの結合親和性はプロカイン<リドカイン<メピバカインの順序で増大した．さらに臨界ミセル濃度の組成依存性からミセル中の麻酔薬組成を求めた．ミセル形成の相図は負の共沸型となり，陰イオン性界面活性剤ミセルと陽イオン性局所麻酔薬カチオン間の強い引力的相互作用を示した．


Thermodynamic Study on Vesicle Formation and Adsorption of Decyltrimethylammonium Decyl Sulfate

The surface tension of an aqueous solution of decyltrimethylammonium decyl sulfate (DeTADeS) was measured as a function of temperature T at various molalities &mcirc; under atmospheric pressure. DeTADeS has been found to form equilibrium multilamellar vesicles (MLV) spontaneously. The surface density, the entropies of adsorption, and the entropy of vesicle formation are evaluated. The mechanism of formation of equilibrium vesicles is investigated from the standpoint of thermodynamics and from the comparison of the results with those of the micelle-forming systems. From the relatively small change of the surface density Gamma;(H) on T at a given &mcirc;, the adsorbed film is implied to be tightly packed due to the strong electrostatic attraction between the polar headgroups. The energy change associated with adsorption from the vesicular state per mole of surfactant Delta(V)(H)u is positive in the entire temperature range; thus, the curved bilayer in MLV is energetically more favorable than the planar adsorbed film. From the negative values of the entropy of vesicle formation Delta(W)(V)s, it is concluded that vesicle formation is driven by enthalpy whereas micelle formation is mostly entropy driven. Copyright 2001 Academic Press.

デシル硫酸デシルトリメチルアンモニウム水溶液の表面張力を大気圧下，温度および活性剤濃度の関数として測定した．この活性剤は自発的にベシクルを形成することが見出された．会合体形成の熱力学量を計算し，結果をミセルを形成する界面活性剤のものと比較した．表面吸着量の小さな温度依存性は吸着膜の密な充填状態を示唆した．また，ベシクル形成のエネルギーとエントロピーの検討からベシクル形成は通常のミセル形成のようなエントロピー駆動ではなく，エンタルピー駆動であることを結論づけた．


Surface Tension Measurements with High Accuracy: Investigation of Accuracy for Automatic Measurements by the Drop Volume Method

表面張力の高精度測定のために必要と考えられる条件を純水の表面張力測定を通して探索した．純水の表面張力を測定誤差の原因となる様々な要因を設定した条件下で行い，それらの要因が表面張力値におよぼす影響を調べた．誤差要因の検討結果をもとにして，考えられる誤差要因を最小限に押さえた装置を製作した．この装置を用いて純水，界面活性剤水溶液および揮発性有機液体の表面張力を測定し，偏差が少なく且つ再現性ある表面張力の吸着平衡値を得ることができた．


Miscibility of Hydrocarbon and Fluorocarbon Surfactants in Adsorbed Film and Micelle

We investigated the miscibility of nonionic hydrocarbon and fluorocarbon surfactants in the adsorbed film and the micelle by surface tension measurements of the aqueous solution. The combination of tetraethyleneglycol monodecyl ether (C10E4) and tetraethyleneglycol mono-1,1,7-trihydrododecafluoroheptyl ether (FC7E4) was chosen because they have the same hydrophilic groups and about the same surface activity. The extent of nonideal mixing was estimated quantitatively in terms of the excess Gibbs energy in the adsorbed film g(H,E) and that in the micelle g(M,E). The excess area per adsorbed molecule, A(H,E), was also evaluated and discussed. The ionic hydrocarbon and fluorocarbon mixed surfactant systems, lithium dodecyl sulfate (LiDS)/lithium perfluorooctane sulfonate (LiFOS) and lithium tetradecyl sulfate (LiTS)/LiFOS systems are also investigated from the standpoint of excess Gibbs energy and excess area. It is also clearly shown that the regular solution approach does not fit in the systems that contain ionic species. Copyright 2001 Academic Press.

非イオン性の炭化水素系界面活性剤(テトラエチレングリコールモノデシルエーテル)とフッ素系界面活性剤(テトラエチレングリコールモノ-1,1,7-トリハイドロドデカフルオロヘプチルエーテル)の吸着膜とミセル中における混和性を表面張力測定から調べた．熱力学的解析から会合体形成の過剰熱力学量を求め，イオン性の炭化水素系界面活性剤-フッ素系界面活性剤混合系のものと比較し，両系の相違を議論した．さらに正則溶液理論はイオン性界面活性剤を含む系には適用できないことを示した．

Journal of Colloid and Interface Science


Interdigitation of Phospholipid Bilayer Membrane and Vesicle-Micelle Transition Induced by Local Anesthetic

局所麻酔薬が誘起するリン脂質二分子膜の指組構造化とベシクル-ミセル転移

局所麻酔薬テトラカイン塩酸塩存在下におけるジパルミトイルフォスファチジルコリン二分子膜の相挙動を示差走査熱量法で調べた．テトラカイン塩酸塩の添加により，二分子膜の指組構造化が観測された．二分子膜相挙動はテトラカイン塩酸塩濃度に依存し，テトラカイン塩酸塩を可溶化したベシクル領域，可溶化ベシクルと両者の混合ミセルの共存領域，混合ミセルのみの領域の3つの会合体領域に分けられた．さらに混合ミセル形成に関連した2種類の新しい転移を見出した．


Effect of Local Anesthetics on the Bilayer Membranes of Dipalmitoylphosphatidylcholine: Interdigitation of Lipid Bilayer and Vesicle-Micelle Transition

The phase transitions of dipalmitoylphosphatidylcholine (DPPC) bilayer membrane were observed by means of differential scanning calorimetry (DSC) as a function of the concentration of local anesthetics, dibucaine (DC x HCl), tetracaine (TC x HCl), lidocaine (LC x HCl) and procaine hydrochlorides (PC x HCl). LC x HCl and PC x HCl depressed monotonously the temperatures of the main- and pre-transition of DPPC bilayer membrane. The enthalpy changes of both transitions decreased slightly with an increase in anesthetic concentration up to 160 mmol kg(-1). In contrast, the addition of TC x HCl or DC x HCl, having the ability to form a micelle by itself, induced the complex phase behavior of DPPC bilayer membrane including the vesicle-to-micelle transition. The depression of both temperatures of the main- and pre-transition, which is accompanied with a decrease in enthalpy, was observed by the addition of TC x HCl up to 21 mmol kg(-1) or DC x HCl up to 11 mmol kg(-1). The pretransition disappeared when these concentrations of anesthetic were added, and the interdigitated gel phase appeared above these concentrations. The appearance of the interdigitated gel phase, instead of the ripple gel phase, brings about the stabilization of the gel phase by 1.8-2.4 kcal mol(-1). In the concentration range of 70-120 mmol kg(-1) TC x HCl (or 40-60 mmol kg(-1) DC x HCl), the enthalpy of the main transition exhibited a drastic decrease, resulting in the virtual disappearance of the main transition. This process includes the decrease in vesicle size with increasing anesthetic concentration, resulting in the mixed micelle of DPPC and anesthetics. Therefore, in this range of anesthetic concentration, the DPPC vesicle solubilized an anesthetic which coexists with the DPPC-anesthetic mixed micelle. Above the concentration of 120 mmol kg(-1) TC x HCl (or 60 mmol kg(-1) DC x HCl), there exists the DPPC-anesthetic mixed micelle. Two types of new transitions concerned with the mixed micelle of DPPC and micelle-forming anesthetics were observed by DSC.

示差走査熱量法を用いてジパルミトイルホスファチジルコリン二分子膜の相転移を4種類の局所麻酔薬塩酸塩(ジブカイン，テトラカイン，リドカイン，プロカイン)濃度の関数として測定した．リドカインおよびプロカインは相転移温度およびエンタルピーを僅かに減少させただけだったが，ジブカインおよびテトラカインの場合には会合体転移を含む複雑な相挙動が見られた．ジブカインあるいはテトラカイン濃度の増加に伴い前転移は消失し，指組み構造ゲル相が出現した．さらなる濃度増加により麻酔薬可溶化ベシクル-混合ミセル共存領域へと移行後，主転移の消失と共に混合ミセルのみの領域に到達するのを観測した．


局所麻酔薬リドカインの表面吸着膜中における非解離-解離分配平衡

局所麻酔薬リドカインの表面吸着膜中における非解離-解離分配平衡

非解離型局所麻酔薬リドカインと解離型局所麻酔薬リドカインカチオンの表面吸着膜中での分配平衡をリドカイン-塩酸混合水溶液の表面張力とpHを測定することにより調べた．熱力学的解析から計算した両者の表面密度から，表面吸着膜中への非解離型リドカインの分配は，非吸着組成，優先的吸着組成および排除組成の3つの組成領域に分割されることがわかった．また，生理的pHでは非解離型が解離型よりも優先的に表面吸着膜に分配することを明らかにした．


局所麻酔薬によるリン脂質二分子膜の相転移温度降下 -pHの影響-

局所麻酔薬によるリン脂質二分子膜の相転移温度降下 -pHの影響-

pHを調節した環境下で局所麻酔薬リドカイン塩酸塩がリン脂質ジパルミトイルホスファチジルコリン二分子膜の相転移温度に与える影響について，光透過率測定により観測した．相転移温度降下に拡張した束一的性質の熱力学関係式を適用して，麻酔薬の膜/水相間の分配係数を見積もった．さらに分配係数のpH依存性から解離型および非解離型リドカインの分配係数に分割した．非解離型は解離型の約38倍の分配係数となり，非解離型麻酔薬の優先的分配を明確にした．


Effect of Local Anesthetics on the Phase Transition Temperatures of Ether- and Ester-Linked Phospholipid Bilayer Membranes

エステル結合型リン脂質ジパルミトイルホスファチジルコリンおよびエーテル結合型リン脂質ジヘキサデシルホスファチジルコリン二分子膜の相転移温度におよぼす5種類の局所麻酔薬塩酸塩(ジブカイン，テトラカイン，ブピバカイン，リドカイン，プロカイン)の影響を調べた．相転移温度降下に束一性の熱力学的関係式を適用して，これら麻酔薬に対する3種類の二相間分配係数を計算した．二分子膜液晶相の分配係数から求めた麻酔薬の標準移行自由エネルギー変化には各麻酔薬の麻酔ポテンシーと良い相関が見られた．


Intra-axonal Continuous Measurement of Lidocaine Concentration and pH in Squid Giant Axon

局所麻酔薬リドカインによるイカ巨大神経軸索中における活動電位の消失と再生を軸索内リドカイン濃度およびpH変化から検討した．活動電位の消失は高いpH(7.8，9.0)のリドカイン投与の時のみで起こり，pH 9.0の時がpH 7.8よりも早く遮断し，回復時間も長くかかった．軸索原形質内の解離型リドカイン濃度はpH 9.0の方がpH 7.8よりも低かった．非解離型リドカインが軸索膜と軸索原形質に移行し，蓄積されることが神経伝導遮断に大きな役割を果たしていることを明確にした．


滴容法の原理に基づく自動界面張力測定装置の開発

滴容法の原理に基づく自動界面張力測定装置の開発

2相液体間の界面張力値を迅速に且つ精度よく求める目的で，滴容法の原理に基づくコンピューター制御の自動界面張力測定装置を開発した．この装置を使用して純粋な水および油間の界面張力を測定し，一定の平衡界面張力値を得た．さらに水相に界面活性剤を溶解した水溶液と油との界面張力，油相に界面活性剤を溶解した油溶液と水との界面張力を測定した．いずれの場合の水/油界面においても界面張力の吸着平衡値が再現性良く得られた．本装置は界面現象の関与する研究に非常に役立つことを示した．


Effect of Unsaturated Acyl Chains on the Thermotropic and Barotropic Phase Transitions of Phospholipid Bilayer Membranes

リン脂質二分子膜の相挙動におよぼす不飽和アシル鎖の効果を高圧光透過法と示差走査熱量法を用いて調べた．飽和アシル鎖への不飽和結合の導入は主転移温度を降下させ，転移体積変化の値を減少させることがわかった．さらに不飽和結合のシス型とトランス型，シス型不飽和結合を導入するアシル鎖の位置(sn-1位あるいはsn-2位)およびsn-2位のアシル鎖中の不飽和結合数の相違は二分子膜の相挙動に大きな影響を与えることを示した．


非解離型及び解離型局所麻酔薬の表面活性の相違

非解離型及び解離型局所麻酔薬の表面活性の相違

非解離型局所麻酔薬の表面活性を調べるために，4種類のアミド型局所麻酔薬(ジブカイン，ブピバカイン，リドカイン，メピバカイン)水溶液の表面張力測定を行った．非解離型麻酔薬の表面密度の値は麻酔薬分子の有する疎水性に比例し，且つそれらの表面活性は対応する解離型のものより非常に大きいことがわかった．また，非解離型麻酔薬の表面活性と麻酔ポテンシーとの間には良い相関関係が存在した．


局所麻酔薬によるDMPE二分子膜の主転移および副転移の相転移温度降下

局所麻酔薬によるDMPE二分子膜の主転移および副転移の相転移温度降下

2種類の局所麻酔薬塩酸塩(テトラカインとプロカイン)がジミリストイルホスファチジルエタノールアミン二分子膜の相転移に与える効果を光透過法で測定した．麻酔薬添加により主転移および副転移温度共に直線的に降下した．また副転移よりも主転移温度が大きな降下を示した．相転移温度降下を熱力学的に解析し，二分子膜の各相間の分配係数差を求めた．麻酔薬の分配は結晶相<ゲル相<液晶相の順序で大きくなった．


Vesicle-Micelle Equilibrium of Anionic and Cationic Surfactant Mixture Studied by Surface Tension

院イオン性界面活性剤(デシル硫酸ナトリウム)と陽イオン性界面活性剤(臭化デシルアンモニウム)の混合水溶液の相挙動を解明した．表面張力-濃度曲線の熱力学的解析より，ミセル-ベシクル相図を作成した．広い組成範囲でベシクルが形成しており，0.9999以上のモル分率にミセル-ベシクル転移が存在する．


Difference in Surface Activities between Charged and Uncharged Local Anesthetics: Correlation with Their Anesthetic Potencies

6種類の非解離型局所麻酔薬の表面活性を麻酔薬水溶液の表面張力測定から調べた．麻酔薬の表面活性は疎水性の大きさの順に大きくなった．この結果を対応する解離型麻酔薬のものと比較し，非解離型麻酔薬は解離型麻酔薬よりも非常に大きな表面活性を有することがわかった．局所麻酔ポテンシーと表面活性間には，解離型麻酔薬よりも非解離型麻酔薬の方がより良い相関関係が見られた．


プラスチック管への局所麻酔薬リドカインの吸着とその神経伝導遮断に及ぼす影響

プラスチック管への局所麻酔薬リドカインの吸着とその神経伝導遮断に及ぼす影響

電気生理実験や薬物投与に用いられるシリコン系樹脂，ポリ塩化ビニル系樹脂，フッ素系樹脂，ポリエチレン樹脂からなるプラスチック管へのリドカインの吸着量とpHの関係を調べた．シリコン系およびポリ塩化ビニル系樹脂ではpHが高くなるとリドカイン吸着量が増し，pH 9の溶液では30分で80 %のリドカインが表面吸着した．電気生理実験でこれらのプラスチック管を用いると有効薬物濃度が著しく変化する．


Membrane-Buffer Partition Coefficients of a Local Anesthetic Tetracaine Monitored by an Anesthetic Sensor

ジミリストイルホスファチジルコリン二分子膜への局所麻酔薬テトラカインの結合をテトラカインカチオン選択性電極を用いて測定した．テトラカインの二分子膜/緩衝液分配係数をpHの関数としてラメラゲル相，リップルゲル相および液晶相に対して決定した．上記分配係数のpH依存性からテトラカインの解離型および非解離型分子種に対する分配係数を計算した．3つの膜状態は解離型より非解離型テトラカインに大きな感受性を示した．


Barotropic phase transitions and pressure-induced interdigitation on bilayer membranes of phospholipids with varying acyl chain-lengths

The bilayer phase diagrams of a series of 1, 2-diacylphosphatidylcholines containing linear saturated acyl chain (C=13, 14, 15, 16, 17 and 18) were constructed by two kinds of high-pressure optical methods. One is the observation of isothermal barotropic phase transition and the other is the isobaric thermotropic phase transition. The temperature of the main transition from the ripple gel (Pbeta') phase to the liquid crystal (Lalpha) phase for each lipid was elevated by pressure. The slope of the temperature-pressure diagram, dT/dP, was in the range of 0.21-0. 23 K MPa-1 depending on the acyl chain length. The temperature of the pretransition from the lamellar gel (Lbeta') phase to the Pbeta' phase for each lipid was also elevated by pressure. The slope of phase boundary, dT/dP, for the pretransition was in the range of 0. 12-0.14 K MPa-1. Both temperatures of the main and pretransition under ambient pressure increased with an increase in acyl chain length. The chain length dependences of the pretransition and main transition temperatures describe smooth curves with no evidence of odd/even discontinuities. Pressure-induced interdigitated gel (LbetaI) phase was observed beyond 300 MPa for 14:0-PC, 175 MPa for 15:0-PC, 100 MPa for 16:0-PC, 80 MPa for 17:0-PC and 70 MPa for 18:0-PC, respectively. The minimum pressure for the interdigitation of lipid bilayer membranes decreased with an increase in acyl chain length in a manner of non-linear relation. The slopes of phase boundary between Lbeta' and LbetaI phases transformed from the negative slope to the positive slope as the pressure increases.

2種類の光透過法を用いて，炭素数13から18までの直鎖の飽和リン脂質ジアシルホスファチジルコリン二分子膜の温度-圧力相図を構築した．常圧下の主転移および前転移温度には偶奇効果は見られず，アシル鎖長の増加に伴い増加した．指組構造ゲル相出現の最小圧力はアシル鎖長の増加と共に非直線的に減少した．また，ラメラゲル相と指組構造のゲル相境界の傾きは圧力の増加と共に負から正へ変化した．

Biochimica et Biophysica Acta (BBA) - Biomembranes


Barotropic phase transitions of dioleoylphosphatidylcholine and stearoyl-oleoylphosphatidylcholine bilayer membranes

In order to understand the effect of cis unsaturation on the thermotropic and barotropic phase behavior of phospholipid bilayer membranes, the phase transitions of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) bilayer membranes were observed by high-pressure optical method. With respect to DOPC bilayer membrane, the so-called main transition between the liquid crystalline (Lalpha) and the lamellar gel (Lbeta) phases was observed in water at above 0 degrees C under high pressure, in addition to the transition between the Lalpha and the lamellar crystalline (L(C)) phases in 50% aqueous ethylene glycol. The pressure of main transition increased linearly with an increase in temperature. Extrapolation of temperature (T)-pressure (P) phase boundary to ambient pressure suggests the temperature of the main transition to be -40.3 degrees C, which has never been found by the DSC method. On the other hand, the temperature of L(C)/Lalpha phase transition in 50% aqueous ethylene glycol was found to be -12.0 degrees C at ambient pressure. The main transition temperatures for DSPC, SOPC and DOPC are 55.6, 6.7 and -40.3 degrees C, respectively, at ambient pressure. The substitution of cis unsaturated chain for saturated chains of DSPC brings about the depression of the main transition temperature by about 48 (+/-1) degrees C for each chain. The volume changes (deltaV) associated with the transitions were calculated from the transition enthalpy (deltaH) and the slope of T-P diagram (dT/dP) by means of the Clapeyron-Clausius equation. The value of deltaV for the main transition of SOPC bilayer membranes was reduced to half the volume change for DSPC bilayers, which means the introduction of the cis double bond in the acyl chain of lipids brings about the reduction of deltaV because of the disordered packing of unsaturated chains in the gel phase of lipid bilayer membranes.

脂質二分子膜の相挙動におよぼすシス位の不飽和結合の影響を調べるために，ジオレオイルホスファチジルコリンとステアロイル-オレオイルホスファチジルコリン二分子膜の相転移を高圧光透過法で観測した．飽和アシル鎖へのシス不飽和結合の導入により大幅な相転移温度降下が見られた．飽和アシル鎖リン脂質と相転移体積を比較して，シス不飽和結合の導入はゲル相内の秩序低下を引き起こし，転移体積値の減少をもたらす．


Volume Properties of Decylammonium Chloride and Micelle-Forming Local Anesthetic Mixtures in the Micelle

陽イオン性界面活性剤(塩化デシルアンモニウム)とミセル形成能を有する局所麻酔薬塩酸塩(ジブカインとテトラカイン)混合系の水溶液の密度を測定し，両者の水中での体積挙動を考察した．両系共に活性剤と麻酔薬分子は単分散およびミセル状態で体積的に理想混合した．またミセル形成の相図の結果から，両分子間に作用する非理想的な分子間相互作用はミセル体積に影響する程には強くないと結論した．


Surface Tension Study on the Molecular-Aggregate Formation of Local Anesthetic Dibucaine Hydrochloride

局所麻酔薬ジブカイン塩酸塩の分子集合体形成を表面張力測定により調べた．熱力学的解析から計算した表面吸着とミセル形成の熱力学量をジブカインと同程度の疎水性を有する直鎖の陽イオン性界面活性剤のものと比較した．表面吸着の熱力学量はかさ高い極性基を持つ活性剤の挙動と類似していたが，ミセル形成の熱力学量は活性剤のものとはかなり異なっていた．


Partitioning of Charged Local Anesthetics into Model Membranes Formed by Cationic Surfactant: Effect of Hydrophobicity of Local Anesthetic Molecules

界面活性剤(塩化デシルアンモニウム)が形成する分子集合体(表面吸着膜およびミセル)中への疎水性の異なる5種類の局所麻酔薬塩酸塩(ジブカイン，テトラカイン，ブピバカイン，リドカイン，プロカイン)の分配を表面張力測定から調べた．疎水性の大きな麻酔薬はこれら集合体中へ分配したが，疎水性の小さな麻酔薬は全く，あるいはほとんど分配しなかった．さらに分配は分子集合体の幾何学的形状に大きく影響を受けることが明確になった．


Barotropic Phase Transitions and Pressure-induced Interdigitation on Bilayer Membrane of Dimyristoylphosphatidylcholine

ジミリストイルホスファチジルコリン多重層ベシクルの定圧昇温相転移と定温加圧相転移を研究した．主転移および前転移温度共に加圧によって上昇した．圧力によって誘起された指組構造のゲル相を300 MPa以上の高圧力領域において観測した．


ジパルミトイルホスファチジルコリン二分子膜と局所麻酔薬の相互作用 --- 示差走査熱量法による研究

示差走査熱量法によりジパルミトイルホスファチジルコリンの相挙動に与える3種類の局所麻酔薬塩酸塩(テトラカイン，リドカイン，プロカイン)の影響について検討した．全ての麻酔薬において添加麻酔薬濃度の増加に伴い主転移および前転移温度は降下した．各麻酔薬による相転移温度降下は麻酔ポテンシーと良い相関関係を示した．さらにテトラカイン高濃度存在下では指組構造のゲル相が誘起された．


原生生物の一種であるゾウリムシ(Paramecium multimicro-nucleatum)に対して麻酔薬を作用させ，それにより起こる行動変化を解析した．全身麻酔薬のアルコール類においてはメタノールから1-ブタノールまでは泳動停止反応が，1-ペンタノールから1-オクタノールまでは繊毛打逆転反応が各々同時に起こった．局所麻酔薬においては繊毛打逆転反応と泳動停止反応の2種類の反応が同時に起こった．


Exclusion of the Local Anesthetic Procaine Hydrochloride from a Surface-Adsorbed Film and Micelle of Decylammonium Chloride

陽イオン性界面活性剤(塩化デシルアンモニウム)が形成する表面吸着膜およびミセル中への局所麻酔薬プロカイン塩酸塩の取り込みを両者の混合水溶液の表面張力測定から調べた．熱力学的解析から求めた表面吸着とミセル形成の相図から，プロカイン塩酸塩は活性剤分子集合体の提供する疎水性環境中には全く移行せず，逆にこれら環境から排除された状態にあることが明らかとなった．


Partitioning of Local Anesthetic Dibucaine into Bilayer Membranes of Dimyristoylphosphatidylcholine

ジミリストイルホスファチジルコリン二分子膜への局所麻酔薬ジブカインの結合をジブカインカチオンセンサーを用いて測定し，ジブカインの二分子膜/緩衝液分配係数を麻酔薬濃度，温度およびpHの関数として決定した．膜の麻酔薬感受性は二分子膜の状態に依存して著しく変化した．分配係数のpH依存性から計算した麻酔薬の解離型および非解離型分子種に対する分配係数は，いづれの膜状態でも非解離型の方が解離型よりも大きくなった．


Thermotropic and Barotropic Phase Transition on Bilayer Membranes of Phospholipids with Varying Acyl Chain-Lengths

2種類の光透過法を用いて，炭素数12から18までの直鎖の飽和リン脂質ジアシルホスファチジルコリン二分子膜の主転移温度を圧力の関数として測定した．主転移温度はいずれのリン脂質に対しても加圧により直線的に増加した．主転移エンタルピーと体積変化はアシル鎖長の増加と共に非直線的に増加した．熱力学量の非直線性なアシル鎖長依存性は，おそらく脂肪アシル鎖の末端基の効果に起因している．


局所麻酔薬リドカインセンサーによるイカ巨大神経軸索内リドカイン濃度のモニタリング

リドカインマイクロセンサーとpHセンサーを用いて，イカ巨大神経軸索内のリドカイン濃度を連続的にモニタリングする方法を確立した．神経軸索内へのリドカインの取込·溶出が軸索外のリドカイン濃度とpHに依存し，しかも可逆的であることを明らかにした．


リン脂質二分子膜のInterdigitationにおよぼす局所麻酔薬テトラカインと圧力の影響

高圧光透過法により，テトラカイン塩酸塩存在下でジパルミトイルホスファチジルコリンおよびジヘキサデシルホスファチジルコリン多重層ベシクルの相転移温度-圧力相図を作成した．両リン脂質の主転移温度はテトラカイン添加で降下し，加圧により上昇し，麻酔作用の圧力拮抗現象が認められた．指組構造のゲル相の出現に関しては，両リン脂質共にテトラカイン添加と加圧では拮抗せず，指組構造のゲル相を安定化する相乗的な効果を示した．


混合ミセル中における界面活性剤と局所麻酔薬(テトラカイン塩酸塩とプロカイン塩酸塩)の体積挙動

界面活性剤(塩化デシルアンモニウム)が形成するミセル中に取り込まれた疎水性の異なる2種類の局所麻酔薬(テトラカイン塩酸塩とプロカイン塩酸塩)の体積挙動を密度測定から調べた．活性剤とテトラカイン分子は体積的な見地から単分散およびミセル状態においてほぼ理想混合した．他方，活性剤とプロカイン分子は単分散状態では体積的に理想混合しているが，ミセル状態では活性剤ミセル中にプロカイン分子は全く取り込まれなかった．


Extremely Strong Interaction of Sodium Decyl Sulfate and Decyltrimethylammonium Bromide in Molecular Aggregates

陰イオン性界面活性剤(デシル硫酸ナトリウム)と陽イオン性界面活性剤(臭化デシルトリメチルアンモニウム)混合系の水溶液中および分子集合体中での熱力学的挙動を電気伝導度並びに表面張力測定から調べた．電気伝導度測定の結果は，臨界ミセル濃度以下の濃度において両者は完全解離の強電解質として振る舞うことを示した．これに対して，集合体中では溶液組成に関わらず，集合体組成が両者の等モル混合物になる極端な非理想的な挙動が観測された．

Journal of Colloid and Interface Science


Incorporation of Micelle-Forming Local Anesthetics into Surface Adsorbed Films and Micelles of Decylammonium Chloride

界面活性剤(塩化デシルアンモニウム)が形成する表面吸着膜とミセル中へのミセル形成能を有する2種類の局所麻酔薬(ジブカイン塩酸塩とテトラカイン塩酸塩)の取り込みを表面張力測定から調べた．両麻酔薬共に吸着膜およびミセルにかなり取り込まれたが，ジブカインの方がテトラカインよりも大きな取り込みが見られた．また，吸着膜とミセルの取り込みを相違を検討した結果，局所麻酔薬のかさ高い極性基は表面吸着よりもミセル形成に有利であることがわかった．


イカ巨大神経軸索内かん流における局所麻酔薬リドカインの伝動麻酔作用に及ぼすpHの影響

イカ巨大神経軸索内かん流法により局所麻酔薬リドカインの伝導麻酔作用を種々のpHで検討した．pH 7ではリドカイン濃度15 mMで活動電位の伝導遮断が起こるが，pH 9では7 mM以上で常に伝導遮断を起こす．解離型リドカイン(陽イオン型)よりも非解離型の方がより容易に細胞膜に作用することが実証された．


Effects of Pressure and Local Anesthetic Tetracaine on Dipalmitoylphosphatidylcholine Bilayers

The temperature-pressure phase diagram of dipalmitoylphosphatidylcholine (DPPC) multilamellar vesicles was constructed in the presence of a local anesthetic tetracaine hydrochloride (TC-HCl). The phase-transition temperatures under various pressures were determined by the method of high-pressure light transmission. The temperature of the main transition from the ripple gel (P'(beta)) to the liquid crystal (L(alpha)) phase was depressed by the addition of TC-HCl and elevated by application of pressure up to 150 MPa. The temperature of the pretransition from the lamellar gel (L'(beta)) to the P'(beta) phase was also depressed by the addition of TC-HCl below ca. 10.0 mmol kg(-1) and elevated by the pressure below ca. 50 MPa. Therefore, pressure-anesthetic antagonism for both phase-transitions was confirmed. The pressure-induced interdigitated gel (L(beta)I) phase has been observed under high pressure above 100 MPa in the absence of TC-HCl. The L(beta)I phase is known to be induced also by a variety of small amphiphilic molecules such as ethanol, benzyl alcohol and TC-HCl. In the presence of TC-HCl ranging in concentration up to 20.0 mmol kg(-1), the L(beta)I phase instead of the P'(beta) phase appeared at higher pressure. Present results revealed that pressure facilitates, rather than antagonizes, the effect of TC-HCl on the occurrence of interdigitated gel phase. Furthermore, two regions of two phase coexistence were observed under high pressure in the presence of TC-HCl. One is probably a region of coexisting L(beta)I and L(alpha) phase, which was found between L(beta)I and L(alpha) phases under various pressures. The other is probably a region of coexisting L'(beta) and L(beta)I phase, which was observed in the presence of TC-HCl up to 10.0 mmol kg(-1) at the pressure above 40 MPa and at the temperature below ca. 35 degrees C.

局所麻酔薬テトラカイン塩酸塩存在下において，ジパルミトイルホスファチジルコリン多重層ベシクルの温度-圧力相図を高圧光透過法によって構築した．主転移および前転移温度共にテトラカイン添加により降下し，加圧で上昇することから麻酔の圧拮抗現象を確認した．他方，テトラカインと加圧は，互いに指組構造のゲル相の出現を促進させた．さらにテトラカイン存在の高圧下において2つの2相共存領域を観測した．

Biochimica et Biophysica Acta (BBA) - Biomembranes


Effects of Pressure and Local Anesthetic Tetracaine on Dihexadecylphosphatidylcholine Bilayer Membrane

局所麻酔薬テトラカイン塩酸塩存在下において，エーテル結合型リン脂質ジヘキサデシルホスファチジルコリン多重層ベシクルの温度-圧力相図を高圧光透過法によって構築した．リップル相の領域はテトラカインと圧力の効果によって狭められ，指組構造のゲル相は両者の効果によって拡張した．麻酔作用の圧拮抗は主転移に対してのみ観測され，前転移に関しては両者の相乗的効果が観測された．


解離型および非解離型局所麻酔薬ジブカインの脂質二重膜/緩衝液 分配係数

解離型および非解離型局所麻酔薬ジブカインの脂質二重膜/緩衝液 分配係数

局所麻酔薬ジブカインカチオンに選択的に応答するイオン選択性電極を用いてジブカインのジミリストイルホスファチジルコリン二分子膜/緩衝液分配係数を麻酔薬濃度，温度，pHの関数として決定した．二分子膜の状態に依存して膜の麻酔薬感受性は著しく変化した．分配係数のpH依存性のデータから見積もった麻酔薬の解離型および非解離型分子種に対する分配係数は，非解離型の方が解離型よりも大きな値を示した．


界面活性剤の表面吸着膜及びミセル中への局所麻酔薬テトラカイン塩酸塩とプロカイン塩酸塩の取り込み

界面活性剤(塩化デシルアンモニウム)が形成する表面吸着膜およびミセル中への局所麻酔薬テトラカイン塩酸塩とプロカイン塩酸塩の取り込みをこれら混合水溶液の表面張力測定から調べた．これら環境中への麻酔薬の取り込みは麻酔薬分子の疎水性に大きく依存し，テトラカイン分子は活性剤が形成した吸着膜やミセル中にかなり取り込まれるが，一方，プロカイン分子は全く取り込まれず，これら疎水性環境中から逆に排除されていることが明らかとなった．


局所麻酔薬リドカイン取込に伴うヤリイカ巨大神経軸索内pHのモニタリング

局所麻酔薬リドカイン取込に伴うヤリイカ巨大神経軸索内pHのモニタリング

リドカインセンサーを用いた電位差測定法と高速液体クロマトグラフィーを用いて，ヤリイカ巨大神経軸索内へのリドカイン移動に伴う軸索内のpH変化を連続的にモニタリングし，軸索内へ移動するリドカインの形態は主として非解離型(塩基型)であることが判明した．


Thermotropic and Barotropic Phase Behavior of Dihexadecylphosphatidylcholine Bilayer Membrane

エーテル結合型リン脂質ジヘキサデシルホスファチジルコリン多重層ベシクルの温度-圧力相図を高圧光透過法により構築した．前転移(指組構造のゲル相からリップルゲル相)温度と主転移(リップルゲル相から液晶相)温度の圧力依存性から，これら相転移に伴う体積変化を算出した．また，得られた結果をエステル結合型リン脂質のものと比較し，エーテル結合型とエステル結合型リン脂質間の相図の相違について議論した．


Tetraphenylborate-Selective Coated Wire Electrode Based on Tetraphenylborate-Alkyltriphenylphosphonium Derivatives

テトラフェニルホウ酸(TPB)イオンをアルキルトリメチルリン酸イオンとのイオン対複合体を用いて，TPBイオンに選択的に応答する被覆線型電極を製作した．2×10-7∼1×10-2 Mの濃度範囲でネルンスト応答し，pH 5.5∼12の間で十分使用できることがわかった．


Differential Scanning Calorimetric Study on the Krafft Phenomenon of Local Anesthetics

6種類の局所麻酔薬のクラフト現象を示差走査熱量法により調べた．得られた結果から各麻酔薬に対してクラフト温度，臨界ミセル濃度およびコアゲル相-ミセル溶液転移に伴うエンタルピー変化を決定した．これらの値をクラフト点を有する直鎖の陽イオン性界面活性剤のものと比較し，局所麻酔薬が有する疎水性の程度を明確にした．さらにテトラカイン塩酸塩とブピバカイン塩酸塩の溶解挙動の相違についてエンタルピー観点から議論した．

Journal of Colloid and Interface Science


Volume Study on the Micelle Formation of Local Anesthetic Dibucaine Hydrochloride and Dodecyltrimethylammonium Chloride Mixtures

局所麻酔薬(ジブカイン塩酸塩)と界面活性剤(塩化ドデシルトリメチルアンモニウム)の混合水溶液の密度測定を行い，混合ミセル中での両者の体積挙動を検討した．ミセル形成の相図からミセル中での両分子の混和性は僅かに非理想的であるが，ミセル形成の体積が両純粋系間を直線的に変化することから，体積的見地からは両者はミセル中で理想混合することが明確となった．

Bulletin of the Chemical Society of Japan


Effect of Counterion on the Surface Adsorption and Volume Behavior of Micelle-Forming Local Anesthetics

ミセル形成能を有する局所麻酔薬ジブカインとテトラカインの表面吸着と水中での体積挙動におよぼす対イオン効果を表面張力測定と密度測定から調べた．対イオンの種類にかかわらず，これらの局所麻酔薬は表面吸着膜の相転移を引き起こし，塩酸塩<臭化水素酸塩<ヨウ化水素酸塩の順序で吸着膜は凝縮した．ミセル形成の体積は対イオンの種類にあまり依存せず，表面吸着とは対照的な結果となった．


麻酔薬センサー法による脂質二分子膜への局所麻酔薬の結合

麻酔薬センサー法による脂質二分子膜への局所麻酔薬の結合

リン脂質ジミルストイルホスファチジルコリン二分子膜への局所麻酔薬ジブカイン塩酸塩の結合を麻酔薬センサー法により解析した．ジブカイン塩酸塩は二分子膜の3つの状態(ラメラゲル相，リップルゲル相，液晶相)に対して，それぞれ異なった結合を示した．結合量の順序はラメラゲル相<リップルゲル相<液晶相となり，二分子膜の状態変化に対応して変化することがわかった．


Effect of Pressure on the Colloidal Solution Behavior of Aqueous Local Anesthetic Tetracaine Solutions

局所麻酔薬テトラカイン塩酸塩とその臭化水素酸塩の水溶液中における溶解挙動に対する圧力効果を光透過率法により調べた．測定結果の温度-圧力図にClapeyron-Clausiusの式を適用して，これらの麻酔薬の水和結晶(コアゲル相)からミセル溶液への相転移に伴う体積変化を決定した．水中での会合体形成の体積変化から，これら麻酔薬は体積的な観点から直鎖の陽イオン性界面活性剤の挙動に類似していることを結論づけた．

Colloids and Surfaces A: Physicochemical and Engineering Aspects


Automatic Surface Tension Measurements of Aqueous Surfactant Solutions by the Drop Volume Method

界面活性剤水溶液の表面張力値を高精度で，迅速に且つ自動的に求める目的で滴容法の原理に基づいた新しい表面張力測定装置を開発した．本装置を用いて，大気圧下，25度で種々の界面活性剤水溶液の表面張力測定を行った．測定した濃度範囲において平衡表面張力値が再現性良く，本装置で得られた．


高速液体クロマトグラフィーによるヒト全血中の局所麻酔薬リドカインの定量

高速液体クロマトグラフィーによるヒト全血中の局所麻酔薬リドカインの定量

高速液体クロマトグラフィーを用いたヒト血液中の局所麻酔薬リドカインを定量する方法を開発した．ヒト血液中のリドカイン濃度が0.2∼20 mMの範囲で，相対標準偏差4 %以内の定量が可能となった．


Thermodynamics of Anesthetic Effect on the Phase Transitions of Lipid Membranes

吸入麻酔薬が脂質二分子膜ベシクルの相転移温度およぼす効果を解析する熱力学関係式を導出した．これらの関係式を吸入麻酔薬によるジパルミトイルホスファチジルコリン二分子膜ベシクルの相転移温度降下に適用し，ラメラゲル相，リップルゲル相，液晶相間の分配係数差および近似的な液晶相への分配係数を計算した．麻酔薬の水相から液晶相への移行に関する標準Gibbs自由エネルギー変化は，それら麻酔薬の最小肺胞濃度と良い相関を示した．


四チオン酸イオンとの酸化還元反応を利用したシステイン，ペニシラミン，アミノエタンチオール及びジチオスレイトールのノンサップレサー型イオンクロマトグラフィー

四チオン酸イオンとの酸化還元反応を利用してチオール化合物をノンサップレサー型イオンクロマトグラフィーにより定量する方法を開発した．システイン，ペニシラミン，アミノエタンチオールおよびジチオスレイトールが2∼100 mMの濃度範囲でチオ硫酸イオンの検量線を用いて定量することができた．


Surface Adsorption and Volume Behavior of Local Anesthetics

6種類の局所麻酔薬塩酸塩水溶液の表面張力と密度を測定し，これら麻酔薬の表面吸着と水中での体積挙動について検討した．大きな疎水性を有する麻酔薬は水溶液中でミセルを形成し，希薄な濃度領域でそれらの表面吸着膜が相転移を起こすのを観測した．また麻酔薬の表面活性と麻酔ポテンシー間には良い相関が存在することを示した．さらに，麻酔薬のミセル形成に関する体積パラメーターを決定した．


局所麻酔薬ジブカインの水溶液中における自己会合

局所麻酔薬ジブカインの水溶液中における自己会合

局所麻酔薬ジブカイン塩酸塩の水溶液中におけるジブカインカチオンと塩化物イオンの両方の活量を両イオンの選択性電極を用いて測定した．臨界ミセル濃度以前の濃度において観測されたネルンスト応答直線からのずれを解析し，ジブカイン塩酸塩は水溶液中で対イオン2個を帯同した三量体を形成することを示した．


Adsorption Behavior of Lanthanum Chloride and Propylammonium Chloride Mixture at Water/Air Interface

3価の無機塩の塩化ランタンと塩化プロピルアンモニウム混合系の表面吸着挙動を表面張力測定から調べた．測定した全組成範囲で塩化ランタンは表面領域から排除され負の吸着を示し，塩化プロピルアンモニウムは逆に正の吸着を示した．これら正負の表面密度の絶対値は組成0.160でほぼ等しくなり，全表面密度はこの組成で見掛け上0となった．

Journal of Colloid and Interface Science


Adsorption Behavior of Propylammonium Chloride and Hexylammonium Chloride Mixture at Water/Air Interface

比較的に表面活性が小さな2種類のアルキルアミン塩酸塩(塩化プロピルアンモニウムと塩化ヘキシルアンモニウム)の混合表面吸着挙動を表面張力測定から調べた．純粋な塩化ヘキシルアンモニウム寄りの組成範囲において，表面活性が大きな塩化ヘキシルアンモニウムが優先的に表面に吸着し，表面活性の小さな塩化プロピルアンモニウムは逆に表面領域から排除され，負の吸着をするのが見られた．


Colloidal Properties of Aqueous Local Anesthetic Tetracaine Solutions

局所麻酔薬テトラカイン塩酸塩水溶液のコロイド的特性をテトラカインカチオンに選択的に応答する被覆線型の選択性電極を用いて調べた．臨界ミセル濃度に対する添加塩および温度効果から，テトラカインミセルの対イオン結合度，ミセル形成のエンタルピー変化を計算した．さらに示差走査熱量測定から，テトラカイン塩酸塩のクラフト現象を観測し，コアゲル-ミセル溶液の転移エンタルピー変化を計算した．

Colloids and Surfaces A: Physicochemical and Engineering Aspects


熱ショック酵母の生育に及ぼす高圧力とエタノ-ルの影響

熱ショック酵母の生育に及ぼす高圧力とエタノ-ルの影響

エタノールを含む培地中の酵母に熱ショックを与え，酵母の耐圧性と耐熱性を調べた．エタノール濃度が増すと酵母の耐圧性と耐熱性は低下した．熱ショック酵母は熱処理しない酵母に比べてエタノール耐性が著しく低下した．熱ショックタンパク質がエタノール変性し，外的ストレスに対する酵母の耐性を低下させると考えた．


Local Anesthetic-Sensitive Electrodes: Preparation of Coated-Wire Electrodes and Their Basic Properties in Vitro

数種類の局所麻酔薬カチオンに選択的に応答する被覆線型電極を開発した．10-5∼10-2 Mの濃度範囲で良好なネルンスト応答を示した．この電極を37 ℃でヒト血漿中の局所麻酔薬濃度の定量に用いた．極めて小型化でき，取り扱いが容易で，応答性に優れているので，この電極のin vivoへの応用は可能と思われる．


Study on the Miscibility of Lithium Tetradecyl Sulfate and Lithium Perfluorooctane Sulfonate in the Adsorbed Film and Micelle

炭化水素系界面活性剤(テトラデシル硫酸リチウム)とフッ素系界面活性剤(ペルフルオロオクタンスルホン酸リチウム)混合水溶液の表面張力を測定した．表面吸着膜組成中では溶液組成に比べてより多く存在する成分が低濃度領域と高濃度領域で逆転するのを見出し，ミセル中では部分的に非混和な組成領域が存在し，2種類のミセルの存在を確認した．さらに炭化水素系活性剤の炭化水素鎖長は混和性に大きな影響を与えることを示した．


局所麻酔薬ブピバカインカチオンに応答する被覆線型電極の試作とその生体での応用

局所麻酔薬ブピバカインカチオンに応答する被覆線型電極の試作とその生体での応用

局所麻酔薬ブピバカインに選択的に応答する小型の被覆線型電極を開発し，ウサギ動脈中に挿入してブピバカイン濃度のモニター用センサーとして応用した．3×10-5∼1×10-2 Mの濃度範囲でネルンスト応答を示し，pH 2∼8の範囲で一定した電位を示し，無機イオンやタンパク質の影響は極めて少ないことがわかった．


Effects of Pressure and Ethanol on the Phase Behavior of Dipalmitoylphosphatidylcholine Multilamellar Vesicles

ジパルミトイルホスファチジルコリン多重膜ベシクルの温度-圧力相図をエタノール存在下と非存在下において構築した．圧力やエタノールに誘起された指組構造のゲル相(interdigitated gel)を観測した．圧力は脂質膜中に指組構造を出現させるエタノールの効果と拮抗するのではなく，むしろその効果を促進させることがわかった．


局所麻酔薬カチオン選択性膜を用いた被覆線型電極を開発した．直径0.8 mmの銅線にPVC膜を塗布した．PVC膜にはテトラフェニルホウ酸と麻酔薬カチオンのイオン対と可塑剤ジオクチルフタレートを含ませた．局所麻酔薬リドカイン，ジブカイン，メピバカインのいずれに対してもネルンスト応答を示した．小型化することが可能であるから，in vivoでの応用の可能性がある．


Study on the Miscibility of Lithium Dodecyl Sulfate and Lithium Perfluorooctane Sulfonate in the Adsorbed Film and Micelle

炭化水素系界面活性剤(ドデシル硫酸リチウム)とフッ素系界面活性剤(ペルフルオロオクタンスルホン酸リチウム)混合水溶液の表面張力測定を行い，表面吸着膜とミセル中での両分子の混和性を考察した．ミセル中では全組成領域で両分子は完全に混合するが，他方ミセル中では両分子部分的に混合し，2種類のミセルを形成することを明らかにした．

Journal of Colloid and Interface Science


大腸菌の生育と伸長に対するエタノ-ルの圧力拮抗

大腸菌の生育と伸長に対するエタノ-ルの圧力拮抗

大腸菌の生育に対して負の効果のある圧力とエタノールが共存する系について，菌の生存率，細胞伸長，およびバイオマスに及ぼす圧力とエタノールの影響を圧力拮抗の観点から検討した．


高圧力下における生体モデル膜の機能

高圧力下における生体モデル膜の機能

リン脂質二分子膜の機能におよぼす圧力効果について検討した．ジパルミトイルホスファチジルコリン二分子膜は，液晶相，ゲルI相，ゲルII相の他に，加圧により指組構造のゲル相(interdigitated相)が出現する．二分子膜の状態は薬物の感受性に差を生ずる．吸入麻酔薬ハロセンの液晶相への分配係数は3390でゲルI相へのそれ(820)に比べて大きい．分配係数の圧力依存性から，麻酔薬の水相から膜への移行体積変化を算出した．

Journal of the Society of Materials Science, Japan


Volume Behavior of Mixed Micelles of Dodecyltrimethylammonium Chloride and Bromide

対イオンのみが異なる2つの界面活性剤，塩化および臭化ドデシルトリメチルアンモニウムの混合物水溶液の密度を精密に測定した．活性剤モノマー混合物の部分モル体積，混合ミセルの部分モル体積，ミセル形成の体積変化を算出した．対イオンの異なる混合系では，ミセル形成の体積変化はミセル組成によらず一定となった．


Coated Wire Electrode Sensitive to Local Anesthetic Cations and Their Application to Potentiometric Determination

局所麻酔薬，プロカイン，テトラカイン，リドカイン，ジブカイン，メピバカイン，ブピバカインに応答する被覆線型電極を開発した．テトラフェニルホウ酸とそれぞれの麻酔薬カチオンのイオン対複合体を可塑剤と共にPVC膜に練り込み感応膜とし銅線を被覆した．10-5∼10-2 Mの濃度範囲でネルンスト応答を示した．電極を用いて電位差滴定を行った．

Bulletin of the Chemical Society of Japan


A Coated Wire Electrode Sensitive to Tetraphenylphosphonium Ion for Measurement of the Mitochondrial Membrane Potential

テトラフェニルホスホニウム(TPP+)イオンに応答する被覆線型電極を開発した．TPP+の10-7∼10-3 Mの濃度範囲でネルンスト応答した．この電極を利用してミトコンドリア膜電位を測定し，ミトコンドリアの呼吸作用の解析に応用した．


Effect of Pressure on the Thermotropic Phase Behavior of Surfactant Assemblies in Water

3種類の同族列陽イオン性界面活性剤の水中で形成する分子集合体の相挙動を160 MPaまでの圧力下で観測し，温度-圧力相図から各相の特徴づけを行った．相転移の熱力学量からクラフト現象を明らかにした．


脂質二分子膜を用いた麻酔作用の圧拮抗モデル

脂質二分子膜を用いた麻酔作用の圧拮抗モデル


Volumetric Behavior and Micelle Formation of Aqueous Surfactant Mixtures

混合ミセルの熱力学を体積挙動に発展応用したもので，2成分混合界面活性剤水溶液の精密密度測定を行い熱力学式の適応性を確かめた．混合系の見かけのモル体積をはじめとし，モノマー混合物の平均部分モル体格，混合ミセルのモル体積，混合ミセル形成の体積変化，混合ミセル中の界面活性剤組成などの情報を引き出すことができた．


脂質二分子膜を用いた麻酔作用の圧拮抗モデル

脂質二分子膜を用いた麻酔作用の圧拮抗モデル

ジミリストイルホスファチジルコリン二分子膜のゲル-液晶相転移温度におよぼす吸入麻酔薬と加圧の効果を圧拮抗モデルの視点から解析した．相転移温度降下から計算した麻酔薬分配係数は加圧により減少した．麻酔薬は加圧により膜から押し出されることを，熱力学的に明らかにした．


Thermotrpic and Pressure - Induced Phase Behavior in a Dodecylammonium Bromide - Water System

界面活性剤-水系の相挙動におよぼす圧力の影響について検討したもので，高圧下では新しい分子集合状態が存在することを明らかにした．示差走査熱量分析で2種類の相転移を観測し，高圧下では光学的方法で，これらの相転移温度の圧力変化を測定した．ミセル溶液，安定コアゲル相，準安定ゲル相の他に35 MPa以上の高圧下で新しいゲル相が出現した．


A Differential Scanning Calorimetric Study of the Thermotropic Phase Behavior of Surfactants Assemblies in Water

示差走査熱量分析法により界面活性剤-水系において3種類の吸熱相転移を観測し，これらの相転移の同定と転移熱力学量の決定を行った．3種類の相転移とは，コアゲル相からミセル溶液，準安定コアゲル相から過冷却ミセル溶液，準安定ゲル相から過冷却ミセル溶液である．準安定コアゲル相は界面活性剤水和結晶の多形によるものとみなされる．

Journal of Colloid and Interface Science


Ion Transport Mediated by Inverted Micellar Aggeregates across a Phosphatidylcholine - Octanol Liquid Membrane

2つのNaCl水溶液を液体膜で仕切った系において，膜透過電位と膜電導度を測定し，液体膜中のイオン輸送について検討した．液体膜には水を飽和させたジパルミトイルホスファチジルコリンのオクタノール溶液を用いた．脂質逆ミセルがイオノフォアとして機能している．示差走査熱量分析により液体膜は18 ℃に吸熱ピークをもつことがわかった．膜透過の温度依存性は18 ℃で変化した．


Monolayers of Triple Long - Chain Salts on the Concentrated NaCl Solution

2本鎖の陽イオンと1本鎖の陰イオンからなる塩，ジアルキルジメチルアンモニウムーアルキルスルホネートの4.4 M食塩水溶液上に展開された単分子膜の表面圧-面積曲線をラングミュア法で測定し，単分子膜の相状態に関して考察を行った．3本のアルキル鎖の炭素数が共に16の塩では，膨張膜の他に3種類の凝縮膜状態が認められ，2つの3重点を観測した．

Bulletin of the Chemical Society of Japan


A Simple Statistical Mechanical Theory for the Mutual Solubility of Fluid Mixtures of Water and Organic Solvents under High Pressure

高圧下において上部および下部臨界溶解温度の両方をもつ液体混合物の相図を説明するために簡単な統計力学理論を提案した．分子間相互作用の自由エネルギーパラメーターの温度依存と剰余体積の圧力依存を仮定することによって，水-2-ブタノール系と水-3-メチルピリジン系の高圧下の相互溶解度の実験データをよく再現する結果を得た．


Enhancement of Counterion Binding to Micelles by Inhalation Anesthetics

ドデシル硫酸ナトリウム(SDS)のミセル溶液中で対イオン(Na+)のミセルへの結合が吸入麻酔薬ハロセンの存在によって促進されることを明白にした．従来23Na-NMR法と電気伝導度法で結果が異なっていたが，麻酔薬ハロセンとSDSのモル比を一定に保ちながらSDS濃度を増すとミセルヘの対イオン結合はハロセンにより強められる結果となった．


生体膜モデル系における麻酔薬の分配係数と作用位置

生体膜モデル系における麻酔薬の分配係数と作用位置

モデル膜系での麻酔薬の分配係数の一評価方法を提案すると共に，麻酔薬が膜のどの部分に取り込まれるかをNMRスペクトル，部分モル体積の結果を基に解明した．相転移温度降下法により分配係数を評価する場合の問題点は麻酔薬のゲル相への溶解を考慮することであり，これに対処した．麻酔薬の作用位置は膜内の非極性部分よりもむしろ膜表面に近い親水性部分であると結論づけた．


The Effect of Pressure on the Micelle/Water Partition of 1-Heptanol. An Interpretation for the CMC Decrease by Solubilization under High Pressure

可溶化による臨界ミセル濃度(cmc)の低下を被可溶化物質のミセル/水分配係数と関連づけ，分配におよぼす圧力効果について検討した．1-へプタノールの添加によるドデシル硫酸ナトリウムのcmc変化を200 MPaまでの圧力範囲で測定し，cmc低下能と分配係数の熱力学関係式を用いて分配係数の圧力依存を評価した．1-ヘプタノールの水相からミセルへの移行体積変化は，部分モル体積の実測結果と一致した．


Benzyl Alcohol Penetration into Micelles, Dielectric Constants of the Binding Site, Partition Coefficient and High - Pressure Squeeze - Out

The absorbance maximum, lambda max, of a local anesthetic, benzyl alcohol, is shifted to longer wavelengths when solvent polarity is decreased. The shift was approximately a linear function of the dielectric constant of the solvent. This transition in electronic spectra according to the microenvironmental polarity is used to analyze benzyl alcohol binding to surfactant micelles. A facile method is devised to estimate the micelle/water partition coefficient from the dependence of lambda max of benzyl alcohol on surfactant concentrations. The effective dielectric constants of the sodium decyl sulfate, dodecyl sulfate and tetradecyl sulfate micelles were 29, 31 and 33, respectively. The partition coefficient of benzyl alcohol between the micelles and the aqueous phase was 417, 610 and 1089, respectively, in the mole fraction unit. The pressure dependence of the partition coefficient was estimated from the depression of the critical micelle concentration of sodium dodecyl sulfate by benzyl alcohol under high pressure up to 200 MPa. High pressure squeezed out benzyl alcohol molecules from the micelle until about 120 MPa, then started to squeeze in when the pressure was further increased. The volume change of benzyl alcohol by transfer from the aqueous to the micellar phase was calculated from the pressure dependence of the partition coefficient. The volume change, estimated from the thermodynamic argument, was 3.5 +/- 1.1 cm3.mol-1 at 298.15 K, which was in reasonable agreement with the partial molal volume change determined directly from the solution density measurements, 3.1 +/- 0.2 cm3.mol-1. Benzyl alcohol apparently solvates into the micelles close to surface without losing contact with the aqueous phase.

局所麻酔薬ベンジルアルコールの紫外吸収極大波長が溶媒の誘電率に依存してシフトすることを利用し，ミセルと結合したベンジルアルコールの微視的溶媒環境とミセルヘの分配係数を見積もる方法を提案した．アルキル硫酸塩ミセルにおける結合サイトの見かけの誘電率は29∼33であることから，ミセル表面近傍と結論した．分配係数は加圧により減少し，ミセルよりの絞り出し効果が認められた．

Biochimica et Biophysica Acta (BBA) - Biomembranes