ANESTHETIC-MEMBRANE INTERACTIONS EVALUATED BY ET(30) SOLVATOCHROMISM AND TAFT'S POLARITY PARAMETERS

Abstract Interactions between volatile anesthetics and dipalmitoyl phosphatidylcholine liposome were investigated spectrophotometrically. Four volatile anesthetics were studied. The anesthetics increased an empirical polarity scale, ET(30), at the liposomal interface. The change of ET(30) was correlated with Taft's generalized polarity parameters. All anesthetics increased the generalized proton donor scale (α) and decreased the generalized polarity scale (π). The decrease in π was attributed to the access of anesthetics with a smaller π value to the liposomal membrane, and the perturbation of hydrogen bonds at the water-liposome interface. The increase in α value was attributed also to the perturbation of hydrogen bonds. We previously reported that anesthetics decreased π and increased β (generalized proton acceptor scale) at the membrane-water interface. In this study, we reported the effect of anesthetics on the remaining Taft's parameter, α The present results support our previous conclusion that anesthetics release bound water molecules from the water-liposome interface.