Fluorescence quenching of gramicidin D in model membranes by halothane

Abstract

Inhaled anesthetics were introduced in surgery over a century ago. To this day, the molecular mechanism of anesthetic action remains largely unknown. However, ion-channels of neuronal membranes are believed to be the most- likely molecular targets of inhaled anesthetics. In the study presented here, we investigated the interaction of a simplified ion-channel system, gramicidin, with halothane, a small haloalkane inhaled anesthetic in various environments. Fluorescence-quenching experiments of gramicidin D in dioleoylphosphatidylcholine (DOPC) large unilamellar vesicles (LUVS) have shown that halothane can directly interact with the ion channel (KSV = 66 M–1). Halothane quenched the fluorescence from tryptophan residues located at the lipid bilayer – aqueous interfaces as well as those tryptophans located deeper in the bilayer. Quenching data from gramicidin D in sodium dodecyl sulfide (SDS) micelles revealed that the tryptophan residues located at the micelle–solvent interface were preferentially quenched by halothane (KSV = 22 M–1). In 1-octanol, fluorescence quenching was observed, but with a lower KSV value (KSV = 6 M–1) than in DOPC LUVS and SDS micelles. Taken together, these results indicate that halothane interactions with gramicidin, mediated by a lipid bilayer, are the strongest, and that the mechanism of anesthetic action may also be lipid-mediated.

Size Effect on the Cytotoxicity of Layered Black Phosphorus and Underlying Mechanisms

“…For the preparation of DOPC vesicles, 0.2 mL (25 g L −1 ) of DOPC chloroform solution was dried in an Erlenmeyer flask with the ultrapure nitrogen gas stream to form a DOPC thin film at the bottom of the flask . The DOPC thin film was subjected to vacuum desiccation for at least 4 h to remove the remaining chloroform in the DOPC layer.…”

Effect of pyrrolidinium based ionic liquid on the channel form of gramicidin in lipid vesicles

“…Earlier, quenching experiments along with the gramicidin in the membrane-bound form as well as in aqueous solution has been performed with different quenchers [15,[40][41][42]. These studies are useful to investigate the relative orientation, the degree of exposure and accessibility of tryptophans residues of proteins in membranes [43].…”

Halothane Solvation in Water and Organic Solvents from Molecular Simulations with New Polarizable Potential Function

“…Halothane is an inhalational general anesthetic listed as a core medicine by the World Health Organization . Despite an impressive body of literature, the exact molecular mechanism of action for general anesthetics remains a hotly debated topic. − Two main explanations have been proposed: one is based on the well-established Overton−Meyer principles relating oil (fat) solubility of general anesthetics and their anesthetic potency, where partitioning of the drug into the membrane alters key physicochemical properties of the lipid bilayer, thereby inhibiting membrane protein function. , With the development of instrumental techniques a second mechanism was proposed emphasizing the importance of protein−drug interaction for the general anesthesia . In particular, a number of ligand-gated ion channels − have been identified to be important targets for halothane and other general anesthetics.…”