Tadayoshi Yoshida

A proton nuclear magnetic resonance study on the release of bound water by inhalation anesthetic in water-in-oil emulsion

Water-in-oil emulsion was prepared from glycerol-alpha-monooleate, n-decane and water, and was used to analyze the behavior of bound water molecules in response to the addition of an inhalation anesthetic, enflurane. The motion of water molecules is monitored by proton nuclear magnetic resonance spectroscopy. To the first approximation, the half-height width of the proton signal of dispersed water is related to the spin-spin relaxation time and represents the motion of the water molecule. It appears that one of the two OH moieties of glycerol-alpha-monooleate forms a hydrogen bond with the water molecule in average. The half-height width of the dispersed water proton showed a maximal value when the glycerol alpha-monooleate/n-decane mole ratio was 4 X 10(-2). The cause of this maximum is not immediately clear, but it is suggested that the assembly mode of glycerol-alpha-monooleate may be different between the lower and higher concentration range. Enflurane decreased the half-height width of the dispersed water, indicating an increase in the motion of water molecules. This results demonstrates that the anesthetic weakened the hydrogen bond between water and glycerol-alpha-monooleate molecules, and released bound interfacial water. It is postulated that dehydration of the interface, as shown by the release of bound water, would interfere with the transport of current-carrying hydrated ions through membranes and may constitute a molecular mechanism of anesthesia.

Evaluation of Induced Electromotive Force of a Carbon Micro Coil

The magnetic sensing ability of a carbon microcoil (CMC) with a 3 to 5 µm diameter and 100 to 1000 µm length was evaluated. Since the CMC has an electrically conductive coiled structure, it was found to induce an alternating electromotive force in an alternating magnetic field, similar to a solenoid coil. The electromotive force of the CMC in an alternating magnetic field has a linear relationship with the frequency of the alternating current supplied to an electromagnet. The value of the electromotive force depends on both the number of windings and the electric resistance of the CMC. When a CMC was rotated in a static magnetic field, the electromotive force generated was also related to the frequency of rotation. From these linear relationships, it appears that the CMC could possibly be used as a magnetic micro coil.

FT-IR spectra of glycine oligomers

Abstract Fourier transform infrared spectra were revisited for glycine oligomers (trimer through hexamer) and polyglycine. Oligomers precipitated from aqueous solutions with acetone existed in the planar zigzag conformation similar to polyglycine I. Infrared spectra for the helical conformation similar to polyglycine II were also obtained for glycine pentamer and hexamer.

Saturable and unsaturable binding of a volatile anesthetic enflurane with model lipid vesicle membranes

Presence of specific receptors for volatile anesthetics has recently been proposed (Evers, A.S. et al. (1987) Nature 328, 157-160) by a finding that halothane uptake by the rat brain was characterized, in part, by saturable binding. We report here that volatile anesthetics bind model lipid membranes also with saturable and unsaturable kinetics. Binding of enflurane to dipalmitoylphosphatidylcholine vesicle membranes was measured by gas chromatography. At low anesthetic concentrations, comparable to the clinical level, the interaction was saturable. After reaching a temporary saturation, a sudden increase in the anesthetic binding to the membrane occurred, when the anesthetic concentration in the aqueous phase exceeded 2.7 mM, or 6.3 x 10(-2) atm partial pressure in the gas phase in equilibrium with the aqueous phase. The secondary binding was linear to the aqueous anesthetic concentrations and was unsaturable to the limit of this study. We also found that enflurane self-aggregated in water above 4 mM. When the aqueous concentration exceeded 6 mM, the aggregation number was about 8. We conclude that the saturable binding indicates adsorption onto the vesicle surface, and the unsaturable binding indicates multilayer stacking of the enflurane molecules, where the initially adsorbed molecules provide the binding sites to the succeeding molecules according to the multilayer condensation kinetics. The tendency of enflurane to self-aggregate in water promotes the multilayer stacking at the surface of the membrane.

Aggregation of polyene antibiotics as studied by electronic absorption and circular dichroism spectroscopies

Abstract The self-association of amphotericin B and hamycin, the heptaene polyene antibiotics, was observed in alcoholic solutions on addition of increasing amounts of water at a studied antibiotics concentration of 1 × 10 −5 M. An increase in the aggregation was noticed in methanolic solutions at and above 65–70% (vol. %) water content. The antibiotics were found to be aggregated at and above 85% water content in propanol. The increased water content required to initiate the aggregation in propanol was related to the more hydrophobic nature of the latter. The aggregation of antibiotics was hindered by the addition of Triton X-100, a non-ionic detergent, at a concentration of 0.5%. The self-association of amphotericin B and hamycin was observed at concentrations of 5 × 10 −7 and 1 × 10 −7 M respectively, in phosphate-buffered saline as detected by the presence of an excitonic doublet in their circular dichroism (CD) spectra. The aggregation was found to be enhanced while the concentration increased up to the studied concentration of 5 × 10 −5 M. The polyene antibiotics existed as monomers in dimethyl sulfoxide(DMSO) at concentrations of 1 × 10 −7 −4.3 × 10 −2 M and 1 × 10 −7 −1 × 10 −2 M for amphotericin B and hamycin respectively, as revealed by their concentration-independent CD spectra.

19F-NMR study on micellar solubilization of a volatile anesthetic halothane: Dose-related biphasic interaction

Abstract Volatile anesthetics, used clinically at present, contain dipole moments in their molecular structure. Although the hydrocarbon core of lipid membranes is proposed to be the anesthetic action site, it is inconceivable that these dipolar molecules mix with highly structured membrane lipids isotropically. Because of the amphiphilicity, these anesthetics are most likely to associate with the hydrophilic polar surface of macromolecules. The present communication deals with the solvation mode of halothane (CF3CHClBr) to sodium dodecyl sulfate micelles estimated by 19F-NMR chemical shifts. Depending upon the halothane concentration, two different modes of halothane interacton with the micelles were identified. At low concentrations, halothane solvated onto the micellar surface according to the Langmuir adsorption isotherm. The binding became temporarily saturated when the halothane concentration was about one-half of the surfactant concentration. When halothane was added further, they started to bind the micelle again, without changing the micellar size. The final number of halothane molecules solvated onto the micelles was about equal to the number of surfactant molecules taht forms the micelle. Apparently, half of the hydrophilic parts on the micellar surface are immediately available for the anesthetic binding. When these sites are filled by the anesthetic molecules, the property of the remaining hydrophilic sites must have been changed. Halothane molecules may bind these modified sites. Another possibility is the condensation kinetics where the bound halothane molecules became the novel binding sites.

Molecular orientation of volatile anesthetics at the binding surface: 1H- and 19F-NMR studies of submolecular affinity

The shift of 1H- and 19F-NMR peaks in the frequency domain was used to resolve the solubilization of volatile anesthetics into sodium dodecylsulfate micelles to submolecular level. Enflurane has protons at both ends of the molecule, and the solubilization parameters (partition coefficients in a broad sense) of each end were estimated by 1H-NMR. The values were: 2130 for the hydrophobic end and 1980 for the hydrophilic end. The hydrophobic end of halothane is CF3, hence 19F-NMR was used: 4330 for the hydrophobic end and 2670 for the hydrophilic end. The ratios of the solubilization parameters between hydrophobic and hydrophilic ends were methoxyflurane 1.9 (Kaneshina et al. (1981) Biochim. Biophys. Acta 647, 223-226), enflurane 1.1, and halothane 1.6. The results indicate that methoxyflurane and halothane adsorb perpendicular to the membrane surface, whereas enflurane molecules stay parallel to the interface. The averaged solubilization parameters of both ends of these anesthetics were in good agreement with their conventional partition coefficients between dipalmitoylphosphatidylcholine (DPPC) membranes and water. The solubilization parameter of chloroform (1H-NMR) was 1580 in agreement with the reported values of DPPC-water partition coefficient.

Counterion binding to micelles measured by sodium-23 NMR relaxation times: Enhancement by anesthetics

Abstract Counterion (Na+) binding to anionic surfactant (monoalkylphosphate) micelles was monitored by 23Na nuclear magnetic resonance spectroscopy using spin-lattice (T1) and spin-spin (T2) relaxation times. The T1 and T2 values were almost identical at all surfactant concentrations within experimental error. At concentrations below the critical micelle concentration (CMC), T1 and T2 showed almost a constant value. A sudden decrease in relaxation times (increase in relaxation rates) occurred at the CMC, as expected. Above the CMC, the relaxation times decreased with the increase in surfactant concentrations. Double reciprocal plots between relaxation times and surfactant concentrations produced rectilinear curves. Extrapolation of the linear portions intersected each other at the CMC. When the surfactant concentration was below the CMC, inhalation anesthetics (chloroform, enflurane, and halothane) did not affect the apparent T2 value even with saturating concentrations. When the surfactant concentration exceeded the CMC, these inhalation anesthetics decreased apparent T2 value dose-dependently, indicating stronger binding of sodium ions. The anesthetics appear to be solubilized at the micelle-water interface and increase hydrophobicity of the interface by replacing water molecules. A decrease in the local dielectric constant by anesthetic molecules may account for the increase in the counterion binding to the micellar surface.

Proton flow along lipid bilayer surfaces: effect of halothane on the lateral surface conductance and membrane hydration

Impedance dispersion in liposomes measures the lateral charge transfer of lipid membrane surfaces. Depending on the choice of frequency between 1 kHz and 100 GHz, relaxation of the counterions at the interface, orientation of the head group, and relaxation of the bound and free water are revealed. This study measured the impedance dispersion in dipalmitoylphosphatidylcholine (DPPC) liposomes at 10 kHz. The surface conductance and capacitance showed breaks at pre- and main transition temperatures. Below the pre-transition temperature, the activation energy of the ion movement was 18.1 kJ.mol-1, which corresponded to that of the spin-lattice relaxation time of water (18.0 kJ.mol-1). At temperatures between pre- and main transition it increased to 51.3 kJ.mol-1, and agreed with 46.2-58.0 kJ.mol-1 of the activation energy of the dielectric relaxation of ice. Because the present system was salt-free, the ions were H3O+ and OH-, hence, their behavior represents that of water. The above results show that below the pre-transition temperature, the conductance is regulated by the mobility of free ions, or the number of free water molecules near the interface. On the other hand when the temperature exceeded pre-transition, melting of the surface-bound water crystals became the rate-limiting step for the proton flow. Halothane did not show any effect on the ion movement when the temperature was below pre-transition. When the temperature exceeded pre-transition, 0.35 mM halothane (equilibrium concentration) decreased the activation energy of the ion movement to 29.3 kJ.mol-1. This decrease indicates that halothane enhanced the release of the surface-bound water molecules at pre-transition. The surface-disordering effect of halothane was also shown by depression of the pre-transition temperature and decrease of the association energy among head groups from 9.7 kJ.mol-1 of the control to 5.2 kJ.mol-1 at 0.35 mM.

Raman spectra and rotational isomerism of dimethylphosphorochloridate and trimethyl phosphate

Abstract The Raman spectra of dimethylphosphorochloridate, (CH3O)2P(O)Cl, and trimethyl phosphate, (CH3O)3P(O), have been measured in the liquid and solid states. Rotational isomerism about the COP(O) bond was investigated on the basis of normal coordinate treatment. For (CH3O)2P(O)Cl, four rotational isomers of (T,G), (T,G′), (G′,G) and (G,G) are present in the liquid state. Two crystalline modifications have been obtained and the molecular conformation is the same as (T,G) form in both the solid phases. The wavenumbers of PCl stretching mode are correlated with the molecular conformation similar to the result for the wavenumbers of XCl (XC and Si) stretching mode. In the case of (CH3O)3P(O), three rotational isomers, C1, Cs and C3, have been found to coexist in the liquid state. Three crystalline modifications are obtained in this molecule and the conformer in these phases is the same as the C1 form.