Peptide‐related alterations of membrane‐associated water: deuterium solid‐state NMR investigations of phosphatidylcholine membranes at different hydration levels

Deuterated water associated with oriented POPC bilayers was investigated before and after the addition of 2 mol% peptide. Membranes in the presences of antimicrobial‐(LAH4), pore‐forming‐ (the segments M2 of influenza A and S4 of the domain I of rat brain sodium channels) or lysine‐containing model peptides (LAK1 and LAK3) were investigated by 2 H and proton‐decoupled 31 P solid‐state NMR. The NMR spectra were recorded as a function of hydration in the range between 15 and 93% relative humidity and of sample composition. In the presence of peptides an increased association of water is observed. A quantitative analysis suggests that the peptide‐induced changes in the lipid bilayer packing have a significant effect on membrane–water association. The quadrupolar splittings of 2 H 2 O at a given degree of hydration indicate that the changes of the water deuterium order parameter are specific for the peptide sequence and the lipid composition. Copyright © 2004 John Wiley & Sons, Ltd.