Exploring Peptide Interactions with Interfacial Water Using Reversed Micelles

Abstract

Water adjacent to biological membranes or macromolecules has properties distinct from bulk water. Many biological processes such as energy transduction or recognition events occur in this interfacial water region. It is critical to understanding these processes that the nature of interactions between polypeptide chains and the interfacial water be elucidated. Water within reversed micelles shows behavior very similar to this biochemically important interfacial water. The small water pools offer an excellent system for studying interfacial water, since there is no large pool of bulk water to obscure the parameters due to the interfacial water. We have been exploring the interactions of polypeptides with interfacial water by solubilizing synthetic model peptides in Aerosol OT (AOT, sodium bis-2-ethylhexyl-sulfosuccinate) reversed micelles and using nuclear magnetic resonance (NMR) and circular dichroism (CD) to analyze the conformations of the peptides. Our results indicate that the model peptides undergo a conformational change in the interfacial water that is induced by the counterions of the AOT headgroups. CD, 1H and 13c NMR parameters enable conformational monitoring of the peptide upon variation of the amount of water in the internal pools. Furthermore, the influence of the presence of the model peptide in the water pool on the state of the water has been explored using NMR and infrared (IR) spectroscopies. We have found evidence of the perturbation of an amount of water that can be qualitatively related to the nature and size of the surface of the solubilized peptide. These results show promise of using reversed micelles to study polypeptide hydration.