Water activity in lamellar stacks of lipid bilayers: "Hydration forces" revisited

Author(s)

Rubim, R. Leite ; Gerbelli, B. B. ; Bougis, K. ; Pinto de Oliveira, C. L. ; Navailles, L. ; Nallet, F. ; de Oliveira, E. Andreoli

• Document type: Journal article
• Source: EUROPEAN PHYSICAL JOURNAL E; v. 39, n. 1, p. 11-pg., 2016-01-25.

Abstract

Water activity and its relationship with interactions stabilising lamellar stacks of mixed lipid bilayers in their fluid state are investigated by means of osmotic pressure measurements coupled with small-angle X-ray scattering. The (electrically neutral) bilayers are composed of a mixture in various proportions of lecithin, a zwitterionic phospholipid, and Simulsol, a non-ionic cosurfactant with an ethoxylated polar head. For highly dehydrated samples the osmotic pressure profile always exhibits the "classical" exponential decay as hydration increases but, depending on Simulsol to lecithin ratio, it becomes either of the "bound" or "unbound" types for more water-swollen systems. A simple thermodynamic model is used for interpreting the results without resorting to the celebrated but elusive "hydration forces". (AU)

• FAPESP's process: 11/16149-8 - Interactions between lipid bilayers - the role of the membrane bending rigidity constant
• Grantee: Rafael Leite Rubim
• Support Opportunities: Scholarships in Brazil - Master