NMR Investigations of the Site of Anesthetic Action

Ursinus College, Collegeville PA

Investigators

Abstract

Description (provided by applicant): The mechanism of general anesthesia is unknown, despite over 100 years of clinical use. An understanding of the molecular basis of anesthetic action is necessary to provide better insight into the selection, design, and administration of general anesthetics. Even the site of anesthetic action is unclear, partly because a wide range of chemical compounds induce anesthesia, including rare gas atoms, alcohols, and steroids. However, it is known that anesthetic potency correlates with lipophilicity. Because of this correlation, an early theory of anesthetic interaction proposed that anesthetics dissolve in the lipid portion of cell membranes modulating the lipid properties to induce anesthesia. Later theories have invoked the hydrophobic portion of membrane proteins as the locus of anesthetic action. Molecular-level information about the site of anesthetic action is needed to distinguish between these theories. Nuclear magnetic resonance (NMR) techniques have advanced to the degree that they may be used to examine the site of anesthetic action. In particular, sensitivity enhancement, polarization transfer, multidimensional, and multinuclear techniques allow for the investigation of previously intractable systems. In these studies the membrane environment will be modeled with small unilamellar vesicles composed of phospholipids, both with and without membrane-spanning peptides to act as model protein channels. Xenon will be one anesthetic studied, both because of its favorable anesthetic properties, and because it is amenable to NMR sensitivity enhancement through a technique known as optical pumping (OP). To study exceptions to the lipophilicity correlation, the site of anesthetic action of a series of n-alcohols will also be determined through polarization transfer, multidimensional, and multinuclear techniques. These experiments will be complemented by computer simulation and molecular modeling techniques, also aimed at understanding the location of interaction of anesthetics in the membrane. This project will determine the site of interaction of anesthetics in model membranes, ultimately leading to insight into the mechanism of anesthesia.