CHARACTERIZATION OF A G(M1)-DEPENDENT SURFACE INTERACTION FOR ALCOHOLWITH DPPC MEMBRANES

A unique surface interaction for perdeuterated ethanol and 1-butanol w ith dipalmitoylphosphatidylcholine (DPPC)/monosialoganglioside (G(M1)) multilamellar vesicles can be detected from the fast exchange averagi ng of the nuclear quadrupole coupling constant of the alcohol in the f ree and bound states using deuterium NMR. At 1.0% perdeuterated ethano l or 0.5% perdeuterated 1-butanol, a small splitting of the alcohol re sonance(s) was detected in the liquid-crystalline phase, but not in th e gel phase of the bilayer. The observed splitting is proportional to the fraction of alcohol bound and is dependent on temperature, alcohol , and G(M1) concentrations. The splitting was only observed in the pre sence of negatively charged G(M1) but not neutral asialoganglioside (a sialo-G(M1)) in DPPC multilamellar vesicles. The observed splitting de creased with the addition of Ca2+ or Mg2+ ions. This effect was revers ed upon the addition of chelating agents. It is proposed that the uniq ue surface interaction for alcohol may result from small surface pertu rbations of the phosphatidylcholine head groups by the negatively char ged sialic moieties of neighboring G(M1) molecules in the bilayer.