Partitioning of anesthetic to bio-molecule and thermodynamic activity

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1.We measured water/gas, and octanol/water partition coefficients of volatile anesthetics by gas chromatography with head space sampler. The thermodynamic parameters were not determined because the results were scattering.2.The UV spectrum of local anesthetic, tetracaine, was measured n standard buffer solution with various concentration of dimylistoyl-phosphatidylglycerol (DMPG). The peak of spectrum shifted to the shorter wave leneth with increasing DMPG concentration. We derived the equation to determine thepartition coefficient of tetracaine between buffer and DMPG, and the spectrum of tetracaine in DMPG lembrane. The effect of temperature, pH and hydrostatic pressure were examined.Results and Discussion : (1)The UV spectrum of tetracaine in the DMPG membrane was measured, and partition coefficients were estimated by changing the membrane concentrations.(2)The partition, coefficient to solid-gel (S-G) decreased at low temperature, but that to liquid-crystalline (L-C) remained constant. When temperature decreased, the difference of partition coefficients between Zr(7and S-G enlarged, and the anesthetic potency increased. The current result successfully explained the paradox in the temperature dependence of local anesthetic potency.(3)The pH affected the UV spectra of tetracaine in membrane below the transition temperature, but did not above the transition temperature. Above the transition temperature, tetracaine molecule penetrated deeply into the membrane being protected from the external pH changes.(4)The volume change of uncharged tetracaine accompanied by the partitioning was not significant. The squeeze-out effect of pressure'failed to explain the pressure reversal of anesthesia.