SPONTANEOUS VESICLE FORMATION AT LIPID BILAYER-MEMBRANES

Unilamellar vesicles are observed to form spontaneously at planar lipi d bilayers agitated by exothermic chemical reactions, The membrane-bin ding reaction between biotin and streptavidin, two strong transmembran e neutralization reactions, and a weak neutralization reaction involvi ng an ''antacid'' buffer, all lead to spontaneous vesicle formation. T his formation is most dramatic when a viscosity differential exists be tween the two phases bounding the membrane, in which case vesicles app ear exclusively in the more viscous phase, A hydrodynamic analysis exp lains the phenomenon in terms of a membrane flow driven by liberated r eaction energy, leading to vesicle formation. These results suggest th at energy liberated by intra- and extracellular chemical reactions nea r or at cell and internal organelle membranes can play an important ro le in vesicle formation, membrane agitation, or enhanced transmembrane mass transfer.