Water Between Lipids: Domains For Peptides Insertion?

Capacitance values of monolayers at different areas denote that in a state at which the area per lipid is above a critical value water path are formed beyond the hydration shell of the lipids.This area increase is 12% of the area for lipids in the expanded state and is comparable to that at which the insertion of proteins and peptides takes place in a variety of lipid composition. Therefore, it is concluded that water paths are formed by expansion implying the entrance of few water molecules into the lipid network. Interestingly some aminoacids having biological activity are able to induce those water paths by interacting with specific groups of the lipids, such as the amine groups in ethanolamines. The kinetics of formation; the thermodynamic and structural properties of those water pockets in the restricted microenvironments framed by lipid groups and its relevance in the selective modulation of the protein-membrane interaction is discussed considering the amount and the state of water induced by the different kinds of groups at the interface region that may act as donor or acceptors in H-bonds, for instance, PO, CO and NH. The analysis is made considering surface pressure and capacitance changes in monolayers at different areas and compared with structural data obtained by means of standard FTIR and biodimensional infrared spectroscopy.We will use this information for a further insight on the insertion of positively charged peptides into lipid membranes as described by molecular dynamics.