Di- and tri-phenyltin chlorides transfer across a model lipid bilayer

摘要

A compound's ability to penetrate the plasma membrane of a cell is the critical parameter that determines its potential to become a biologically potent factor.A well-known group of organotin compounds that exhibit toxic properties in relation to biological systems are phenyltins.There are as yet no studies that in a direct manner have established whether organotin compounds such as diphenyltin dichloride (DPhT) and triphenyltin chloride (TPhT) diffuse,or not,through the lipid bilayer,although we know that at least some organotins absorb in both liposome and biological membranes.In this paper we present a series of experiments that show transfer of these compounds across the lipid membrane using the stopped-flow technique.The results obtained demonstrate that DPhT and TPhT first adsorb onto the lipid bilayer surface,in a diffusion-controlled manner and within a very short time (0.05 s),whereas the membrane crossing was observed to be on the order of a minute.The adsorption process was easily fitted with a single exponential for both the compounds studied,indicating a single process phenomenon.The longer time kinetics (characteristic of membrane crossing) showed a complex dependence on compound concentration and the presence of cholesterol in the membrane.On passing from the outer to the inner surface of the bilayer,organotins undergo desorption and enter the liposome interior,which has been shown in lipid monolayer desorption studies.In conclusion,it can be stated that amphiphilic DPhT and TPhT permeate the liposome membrane.