The Interfacial behaviour of peptides over long time scales

Peptides are frequently used as models for membrane proteins due to their accessibility and low molecular weight, both of which facilitate the interpretation of complex spectroscopic data. Membrane proteins are recycled in vivo with half-lives ranging from minutes to days. It is therefore of interest to examine the behaviour of peptides in model membranes over extended periods in order to determine whether these systems reach equilibrium and remain stable. This timescale is seldom examined in studies using model peptides. We have examined kinetics of defensin HNP-2 binding to aligned membranes by both fluorescence spectroscopy and linear dichroism spectroscopy. Changes in membrane alignment were found to occur over a period of hours to days. The reactivity of peptides towards membranes has been examined using melittin. Acyl transfer from phospholipids to the peptide was found to occur over a period of several days. Some of these observations challenge preconceptions concerning the behaviour of peptides at the membrane interface.