MEMBRANE HYDRATION AND STRUCTURE ON A SUBNANOMETER SCALE AS SEEN BY HIGH-RESOLUTION SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE - POPC AND POPC C(12)EO(4) MODEL MEMBRANES/

The position on a subnanometer scale and the dynamics of structurally important water in model membranes was determined using a combination of proton magic-angle spinning NMR (MAS) with two-dimensional NOESY NM R techniques. Here, we report studies on phosphocholine lipid bilayers that were then modified by the addition of a nonionic surfactant that is shown to dehydrate the lipid. These studies are supplemented by C- 13 magic-angle spinning NMR investigations to get information on the d ynamics of segmental motions of the membrane molecules. It can be show n that the hydrophilic chain of the surfactant is positioned at feast partially within the hydrophobic core of the lipid bilayer. With the a bove NMR approach, we are able to establish molecular contacts between water and the lipid headgroup as well as with certain groups of the h ydrocarbon chains and the glycerol backbone. This is possible because high resolution proton and C-13-NMR spectra of multilamellar bilayer m embranes are obtained using MAS. A phase-sensitive NOESY must also be applied to distinguish positive and negative cross-peaks in the two-di mensional plot. These studies have high potential to investigate membr ane proteins hydration and structural organization in a natural lipid bilayer surrounding.