ANESTHETIC-MEMBRANE INTERACTIONS EVALUATED BY E(T)(30) SOLVATOCHROMISM AND TAFTS POLARITY PARAMETERS

Interactions between volatile anesthetics and dipalmitoyl phosphatidyl choline liposome were investigated spectrophotometrically. Four volati le anesthetics were studied. The anesthetics increased an empirical po larity scale, E(T)(30), at the liposomal interface. The change of E(T) (30) was correlated with Taft's generalized polarity parameters. All a nesthetics increased the generalized proton donor scale (alpha) and de creased the generalized polarity scale (pi). The decrease in pi was at tributed to the access of anesthetics with a smaller a value to the li posomal membrane, and the perturbation of hydrogen bonds at the water- liposome interface. The increase in alpha value was attributed also to the perturbation of hydrogen bonds. We previously reported that anest hetics decreased pi and increased beta (generalized proton acceptor sc ale) at the membrane-water interface. In this study, we reported the e ffect of anesthetics on the remaining Taft's parameter, alpha. The pre sent results support our previous conclusion that anesthetics release bound water molecules from the water-liposome interface. (C) 1994 Acad emic Press, Inc.