NEUTRALIZED SURFACTANT PAIR DOMAINS IN POSITIVELY CHARGED VESICLES - MODELING OF PROPOSED MOSAIC MEMBRANE ORGANIZATION

Cosonication of dioctadecyldimethylammonium bromide (DODAB) and [CH2=CHC6H4CONH(CH2) 11O][n-C16H13O]PO2 --(VBAP) led to the formation of long-lasting, closed-bilayer vesicles. The obtained data supported the existence of single-population vesicles containing VBAP-DODAB ion pairs in the matrix of positively charged, closed-surfactant vesicles. Furthermore, the ion pairs clustered in the matrix of the vesicles. The observed 31P NMR and absorption spectroscopy, as well as the phase transition temperature behavior, can be accommodated in terms of two models. The first model involves the formation of reversed micelles from cone-shaped surfactant ion pairs. The second model is discussed in terms of hemispheric bulges on the vesicles which contained domains of VBAP-DODAB ion pairs. Arguments have been presented in favor of the latter model, which is likened to the proposed "mosaic" organization prevailing in biological membranes. © 1990 American Chemical Society.