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H Kamaya

Publications and source records attributed to H Kamaya.

15 recordsLinked to original sources
PubMed1992

Alcohols dehydrate lipid membranes: an infrared study on hydrogen bonding.

The effects of alcohols (methanol, ethanol, and n-butanol) on the hydrogen bonding of dipalmitoylphosphatidylcholine (DPPC) were studied by Fourier-transform infrared spectroscopy (FTIR) in water-in-oil (carbon tetrachloride) reversed micelles. The bound O-H stretching mode of water, bonded to DPPC, appeared as a broad band at around 3400 cm-1. The O-H bending mode of this complex appeared as a weak broad band at 1644 cm-1. No free O-H signal was observed. When alcohols were added, a part of DPPC-bound water was replaced by the alcohols. The released 'free' water appeared at 3680 cm-1. This free O-H stretching band represents water-alcohol complex. A new broad band of O-H stretching appeared at 3235 cm-1, which represents the alcohol molecules bound to the phosphate moiety of DPPC. When the alcohol concentration was increased, the intensities of the free O-H stretching and bending bands increased. The P = O- antisymmetric stretching band at 1238 cm-1 became broader and shifted to lower frequencies. This means that alcohols interacted with the phosphate moiety and replaced the bound water. In the deconvoluted spectra of the C = O stretching mode, the ratio between the free sn-2 and the hydrogen-bonded sn-2 bands increased; a part of the bound water at the sn-2 carbon in the glycerol skeleton is also released and the free sn-2 signal increased. From the change in the intensity of the P = O- stretching band, the partition coefficients of alcohols between the phosphate region of DPPC and water were estimated: methanol 7.8, ethanol 16.7 at 22.0 degrees C in mole fraction bases. In molality, these values translates into methanol 0.21 and ethanol 0.45. These results indicate that short-chain alcohols interact with lipid membranes at the phosphate moiety at the hydrophilic head, weaken the membrane-water interaction, and destabilize membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Biphasic effects of alcohols on the phase transition of poly(L-lysine) between alpha-helix and beta-sheet conformations.

Poly(L-lysine) exists as a random-coil at neutral pH, an alpha-helix at alkaline pH, and a beta-sheet when the alpha-helix poly(L-lysine) is heated. The present Fourier-transform infrared (FTIR) study showed that short-chain alcohols (methanol, ethanol, and 2-propanol) partially transformed alpha-helix poly(L-lysine) to beta-sheet when their concentrations were low. At higher concentrations, however, these alcohols reversed the reaction, and the alcohol-induced beta-sheet was transformed back to alpha-helix structure. The reversal occurred at 1.40 M methanol, 0.96 M ethanol, and 0.55 M 2-propanol. The alcohol effects on the secondary structure were further investigated by circular dichroism (CD) on the thermally induced beta-sheet poly(L-lysine). Methanol, ethanol, and 1-propanol, but not 1-butanol, shifted the negative mean-residue ellipticity at 217 nm of the beta-sheet poly(L-lysine) to the positive side at low concentrations of the alcohols and to the negative side at high concentrations. With 1-butanol, only the positive-side shift was observed. The positive-side shift at low concentrations of alcohols indicates enhancement of the hydrophobic interactions among the side chains of the polypeptide in the beta-sheet conformation. The negative-side shift indicates a partial transformation to alpha-helix. The shift from the positive to negative side occurred at 7.1 M methanol, 4.6 M ethanol, and 3.1 M 1-propanol. The alcohol concentrations for the beta-to-alpha transition were higher in the CD study than in the IR study.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗
PubMed1992

Lateral conductance parallel to membrane surfaces: effects of anesthetics and electrolytes at pre-transition.

The effects of dilute salts and anesthetics were studied on the impedance dispersion in the dipalmitoylphosphatidylcholine (DPPC) liposomes. Below the pre-transition temperature, the apparent activation energy for conductance in DPPC-H2O without salts was equivalent to pure water, 18.2 kJ mol-1. This suggests that the mobile ions (H3O+ and OH-) interact negligibly with the lipid surface below the pre-transition temperature. At pre-transition temperature, the apparent activation energy of the conductance decreased by the increase in the DPPC concentrations. The effects of various salts (LiCl, NaCl, KCl, KBr, and KI) on the apparent activation energy of the conductance were studied. Changes in anions, but not in cations, affected the activation energy. The order of the effect was Cl- less than Br- less than I-. Cations appear to be highly immobilized by hydrogen bonding to the phosphate moiety of DPPC. The smaller the ionic radius, the more ions are fixed on the surface at the expense of the free-moving species. The apparent activation energy of the transfer of ions at the vesicle surface was estimated from the temperature-dependence of the dielectric constant, and was 61.0 kJ mol-1 in the absence of electrolytes. In the presence of electrolytes, the order of the activation energy was F- greater than Cl- greater than Br- greater than I-. When the ionic radius is smaller, these anions interact with the hydration layer at the vesicle surface and the ionic transfer may become sluggish. In the absence of electrolytes, the apparent activation energy of the dielectric constant decreased by the increase in halothane concentrations. In the presence of electrolytes, however, the addition of halothane increased the apparent activation energy. We propose that the adsorption of halothane on the vesicle surface produces two effects: (1) destruction of the hydration shell, and (2) increase in the binding of electrolytes to the vesicle surface. In the absence of electrolytes, the first effect predominates and the apparent activation energy is decreased. In the presence of electrolytes, the latter effect predominates and the apparent activation energy is increased.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Alcohol interaction with high entropy states of macromolecules: critical temperature hypothesis for anesthesia cutoff.

Nerve excitation generates heat and decreases the entropy (review by Ritchie and Keynes (1985) Q. Rev. Biophys. 18, 451-476). The data suggest the existence of at least two thermodynamically identifiable states: resting and excited, with a thermotropic transition between the two. We envision that nerve excitation is a transition between the two states of the excitation machinery consisting of proteins and lipids, rather than the sodium channel protein alone. Presumably, both proteins and lipids change their conformation at excitation. We proposed (Kaminoh et al. (1991) Ann. N.Y. Acad. Sci. 625, 315-317) that anesthesia occurs when compounds have a higher affinity to the resting state than to the excited state of excitable membranes, and that there is a critical temperature above which the affinity to the excited state becomes greater than to the resting state. When the temperature exceeds this critical level, compounds lose their anesthetic potency. We used thermotropic phase-transition of macromolecules as a model for the excitation process. Anesthetic alcohols decreased the main transition temperature of dipalmitoylphosphatidylcholine (DPPC) membranes and also the temperature of the alpha-helix to beta-sheet transition of poly(L-lysine). The affinity of alcohols to the high- and low-temperature states of the DPPC membranes were separately estimated. The difference in the affinity of n-alcohols to the liquid (high-temperature) and solid (low-temperature) states correlated with their anesthetic potency. It is not the total number of bound anesthetic molecules that determines the anesthesia, rather, the difference in the affinity between the higher and lower entropy states determines the effects. The critical temperatures of the long-chain alcohols were found to be lower than those of the short-chain alcohols. Cutoff occurs when the critical temperature of long-chain alcohols is below the physiological temperature, such that the anesthetic potency is not manifested in the experimental temperature range.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

The alpha-helix to beta-sheet transition in poly(L-lysine): effects of anesthetics and high pressure.

Poly(L-lysine) exists in a random-coil formation at a low pH, alpha-helix at a pH above 10.6, and transforms into beta-sheet when the alpha-helix polylysine is heated. Each conformation is clearly distinguishable in the amide-I band of the infrared spectrum. The thermotropic alpha-to-beta transition was studied by using differential scanning calorimetry. At pH 10.6, the transition temperature was 43.5 degrees C and the transition enthalpy was 170 cal/mol residue. At pH 11.85, the measurements were 36.7 degrees C and 910 cal/mol residue, respectively. Volatile anesthetics (chloroform, halothane, isoflurane and enflurane) partially transformed alpha-helix polylysine into beta-sheet. The transformation was reversed by the application of hydrostatic pressure in the range of 100-350 atm. Apparently, the alpha-to-beta transition was induced by anesthetics through partial dehydration of the peptide side-chains (beta-sheet surface is less hydrated than alpha-helix). High pressure reversed this process by re-hydrating the peptide. Because the membrane spanning domains of channel and receptor proteins are predominantly in the alpha-helix conformation, anesthetics may suppress the activity of excitable cells by transforming them into a less than optimal structure for electrogenic ion transport and neurotransmission. Proteins and lipid membranes maintain their structural integrity by interaction with water. That which attenuates the interaction will destabilize the structure. These data suggest that anesthetics alter macromolecular conformations essentially by a solvent effect, thereby destroying the solvation water shell surrounding macromolecules.

Anesthetics↗
PubMed1991

High pressure antagonism of alcohol effects on the main phase-transition temperature of phospholipid membranes: biphasic response.

The combined effects of high pressure (up to 300 bar) and a homologous series of 1-alkanols (ethanol C2 to 1-tridecanol C13) were studied on the main phase-transition temperature of dipalmitoylphosphatidylcholine (DPPC) vesicle membranes. It is known that short-chain alkanols depress and long-chain alkanols elevate the main transition temperature. The crossover from depression to elevation occurs at the carbon-chain length about C10-C12 in DPPC vesicle membranes coinciding with the cutoff chain-length where anesthetic potency suddenly disappears. Alkanols shorter than C8 linearly decreased the transition temperature and high pressure antagonized the temperature depression. Alkanols longer than C10 showed biphasic dose-response curves. High pressure enhanced the biphasic response. In addition, alkanols longer than the cutoff length depressed the transition temperature under high pressure at the low concentration range. These non-anesthetic alkanols may manifest anesthetic potency under high pressure. At higher concentrations, the temperature elevatory effect was accentuated by pressure. This biphasic effect of long-chain alkanols is not related to the 'interdigitation' associated with short-chain alkanols. The increment of the transition temperature by pressure was 0.0242 K bar-1 in the absence of alkanols. The volume change of the transition was estimated to be 27.7 cm3 mol-1. This value stayed constant to the limit of the present study of 300 bar.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

A statistical mechanical analysis of the effect of long-chain alcohols and high pressure upon the phase transition temperature of lipid bilayer membranes.

Long-chain n-alcohols decrease the main phase-transition temperature of lipid vesicle membranes at low concentrations but increase it at high concentrations. The nonlinear phenomenon is unrelated to the interdigitation and is analyzed by assuming that alcohols form solid solutions with solid as well as liquid phases. The biphasic response originates from the balance of the free energy difference of alcohols in the liquid and solid membranes (delta gA) and the alcohol-lipid interaction free energy difference (delta u) between the two phases. When delta gA less than 0 and delta u greater than 0, or delta gA less than delta u less than 0, the transition temperature decreases monotonously according to the increase in the alcohol concentration. When delta gA greater than 0 and delta u less than 0, or delta gA greater than delta u greater than 0, it increases monotonously. Biphasic response occurs with a minimum temperature when delta u greater than delta gA greater than 0, and with a maximum temperature when delta u less than delta gA less than 0. When the alcohol carbon-chain length becomes closer to the lipid carbon-chain length, delta u is equalized by delta gA, and the temperature minimum of the main transition is shifted to extremely low alcohol concentrations. Hence, long-chain alcohols predominantly elevate the main transition temperature and lose their anesthetic potency. High pressure decreased both delta gA and delta u. Presumably, high pressure improves the packing efficiency of liquid membranes and decreases the difference between the solid and liquid membrane properties.

Alcohols↗
PubMed1991

Interfacial dehydration by anesthetics: an electrocapillary study of surface charge density of adsorbed monolayer.

We have proposed that anesthetics destruct the hydration shell of macromolecules irrespective of lipid membranes or proteins. These macromolecular structures are supported by the hydrogen-bonded matrix of water molecules. A loss of this support destabilizes the membranes and proteins. The disordered structures are suboptimal for the assigned biological functions, and anesthesia may ensue. We postulated that the dehydration is prompted mainly by the decrease in the interactions of the surface charges with the water dipole. To prove or disprove the above hypothesis, this study measured the effect of volatile anesthetics (chloroform, halothane, and enflurane) on the surface charge density in adsorbed monolayers by an electrocapillary method. The oil phase was methylisobutylketone (MIBK) with cetyltrimethylammonium chloride (CTAC). The aqueous phase was 0.1 M NaCl. The anesthetics decreased the surface charge density, and the effect paralleled the clinical anesthetic potency. At concentrations that induce surgical stage anesthesia in 50% of the population, these anesthetics reduced the surface charge density by 5%.

Adsorption↗
PubMed1991

Anesthetic-protein interaction: effects of volatile anesthetics on the secondary structure of poly(L-lysine).

Effects of volatile anesthetics (chloroform, halothane, and enflurane) on the secondary structure of poly(L-lysine) were analyzed by circular dichroism (CD). The relative proportions among alpha-helix, beta-sheet, and random-coil conformations were calculated by the curve-fitting method on the CD data. Volatile anesthetics partially transformed alpha-helix to beta-sheet but not to random-coil under the present experimental condition. When expressed by the anesthetic partial pressures in the gas phase in equilibrium with the solution, the values that partially transformed alpha to beta conformation by 10% were 1.1 x 10(-2), 4.7 x 10(-2), and 7.9 x 10(-2) atm for chloroform, halothane, and enflurane, respectively. The order of potency is in reasonable agreement with the order of the anesthetic potencies of the agents. The alpha-to-beta transition was completely reversible when anesthetics were purged by nitrogen gas. Volatile anesthetics disrupted the hydrogen bonds of alpha-helix backbones and rearranged them to form the beta-sheet conformation. The beta-sheet conformation is stabilized mainly by the hydrophobic interaction among methylene side groups of poly(L-lysine). Volatile anesthetics promoted the transition by enhancing the hydrophobic interaction among side-chains and by rearranging the hydrogen bonds in the peptide backbone.

Chloroform↗
PubMed1979

Antagonism between high pressure and anesthetics in the thermal phase-transition of dipalmitoyl phosphatidylcholine bilayer.

The antagonizing action of hydrostatic pressure against anesthesia is well known. The present study was undertaken to quantitate the effects of hydrostatic pressure and anesthetics upon the phase-transition temperature of dipalmitoyl phosphatidylcholine vesicles. The drugs used to anesthetize the phospholipid vesicles included an inhalation anesthetic, halothane, a dissociable local anesthetic, lidocaine and an undissociable local anesthetic, benzyl alcohol. All anesthetics decreased the phase-transition temperature dose-dependently. In the case of lidocaine, the depression was pH dependent and only uncharged molecules were effective. The application of hydrostatic pressure increased the phase-transition temperature both in the presence and the absence of anesthetics. The temperature-pressure relationship was linear over the entire pressure range studied up to 340 bars. Through the use of Clapeyron-Clausius equation, the volume change accompanying the phase-transition of the membrane was calculated to be 27.0 cm3/mol. Although the anesthetics decreased the phase-transition temperature, the molar volume change accompanying the phase-transition was not altered. The anesthetics displaced the temperature-pressure lines parallel to each other. The mole fraction of the anesthetics in the liquid crystalline membrane, calculated from the van't Hoff equation, was independent of pressure. This implies that pressure does not displace the anesthetics from the liquid membrane, and the partition of these agents remains constant. The volume change of the anesthetized phospholipid membranes is entirely dependent upon the phase-transition and not on the space occupied by the anesthetics.

Anesthetics↗
PubMed1979

Hydrophilic region of lecithin membranes studied by bromothymol blue and effects of an inhalation anesthetic, enflurane.

A pH-indicator dye, bromothymol blue, was used to probe the hydrophilic surface of dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine bilayer vesicles. The apparent pK of the surface-adsorbed dye was larger than the bulk pK value. The contribution of the choline positive charge on the dissociation constant of the dye adsorbed on the vesicle surface was estimated by screening the charge interaction with 2 M KCl. The effective surface potentials interacting with the dye were thus estimated to be 33.2, 45.6, and 46.8 mV, respectively, for the dimyristoyl-, dipalmitoyl-, and distearoylphosphatidylcholine vesicles. From the differences between the obtained effective potentials and the calculated surface potentials of the charge-determining plane of the choline head, the distances between the prototropic part of the dye and the choline charge-determining plane were estimated to be 10.5, 8.0, and 7.8 A, respectively. These values were obtained at 25 degrees C; the dimyristoylphosphatidylcholine membrane was in the liquid-crystalline phase and the other two were in the solid gel phase. Addition of an inhalation anesthetic, enflurane, decreased the distance in the dimyristoylphosphatidylcholine vesicles and increased the distance in the dipalmitoyl- and distearoylphosphatidylcholine vesicles. The increase of precessional motion of choline head by the inhalation anesthetic is apparently responsible for the changes.

Bromthymol Blue↗
PubMed1977

Reversible and irreversible inhibition by anesthetics of the calcium-induced luminescence of aequorin.

The actions of various kinds of so-called membrane-stabilizing drugs on Ca2+-induced flash intensity of purified aequorin, a photoprotein obtained from Aequorea aequorea, were examined. All drugs used in this experiment, including inhalational anesthetics, tetracaine, chlorpromazine, and morphine, depressed flash intensity, and the inhibition increased with time. The inhibition followed a mixture of reversible and irreversible kinetics. A method of analyzing irreversible kinetics is presented. The dissociation constants for reversible inhibition and the rate constants for irreversible inhibition are presented for each agent.

Aequorin↗
PubMed1976

Molecular mechanism of inhibition of firefly luminescence by local anesthetics.

The kinetics of the action of local anesthetics upon firefly luciferin and luciferase systems is presented. Clinical concentrations of local anesthetics inhibited this ATP-induced luminescence in a dose-dependent manner. From the effects of temperature and pH upon the inhibitory action of the local anesthetics, it is concluded that hydrophobic ligand-enzyme interaction is the predominant cause of the inhibition, but hydrophilic interaction also contributes to the inhibition to a lesser degree. A molecular theory of anesthesia is outlined which postulates that release of electrostricted water molecules from the hydrophilic parts of the enzyme due to the protein conformational changes induced by anesthetics is the cause of the decreased luminescence. A similar mechanism is expected to occur at the cell membrane, which probably dehydrates the sodium channel and suppresses the conductance of this ion across the membrane. These events lead to a volume expansion of the total system, and the system becomes reactive to a pressure which reverses the anesthesia by shifting the equilibrium to the nonanesthetized original volume. The pressure antagonism of anesthesia can be explained by this overall volume expansion and not by a mere swelling of the cell membrane.

Anesthetics, Local↗
PubMed1976

Combined effects of dissociable and undissociable local anesthetics upon ATP-induced firefly bioluminescence.

Combined effects of two drugs present simultaneously are usually expressed as summation, synergism or potentiation, and antagonism. When the sum of the effects of each drug present separately equals the combined effect of the two drugs present simultaneously, the action is called additive or summation. However, the expected value of the sum of each effect of drugs present alone has not been well defined. In this report, the thearetical value of the expected sum of each effect of two inhibitors is given and a graphical method is presented to visualize summation, synergism, and antagonism. The inhibitory effects of a dissociable local anesthetic, tetracaine, and an undissociable local anesthetic, benzyl alcohol, upon a soluble firefly luminescent system were analyzed according to the above theory. The results clearly indicate that the action of these two classes of local anesthetics is pure additive or summation.

Adenosine Triphosphate↗