Divalent cations promote transversal perturbations in lipid bilayers of sonicated vesicles

DISALVO. E ANIBAL

BIOELECTROCHEMISTRY

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 1984 vol. 11 p. 145 - 154

1567-5394

The effect of mono- and divalent cations and anions on the chemical shift of the phospholipid polar head groups of egg phosphatidylcholine sonicated vesicles was investigated by means of 13P nuclear magnetic resonance spectroscopy (13P n.m.r). Ca2+ inside the vesicles causes an upfield shift of the 31P n.m.r resonances of the inner monolayer lipid molecules, when compared with vesicles containing Na+. On the other monolayer, Ca2+ can only promote an upfield shift of the corresponding phosphate groups if there is Ca2+ inside the vesicle. The binding of Ca2+ on the outer monolayer of the vesicle bilayer depends on the ionic composition of the inner solution. This effect can be explained as a transversal bilayer perturbation which is correlated with the hydration characteristics of the ionic species. The results are qualitatively interpreted with an extension of the kink model proposed by Traüble and the properties of the electric double layers of lipid interphases.