MYELIN MODEL MEMBRANES ON SOLID SUBSTRATES

The molecular organization within multilayers of myelin basic protein (MBP) and acidic phospholipids was investigated. The samples were prep ared by Langmuir-Blodgett transfer of protein/lipid precursor Langmuir films from the air/water interface after binding of MPB from the subp hase. The presence of MBP within the multilayer was directly proven by Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) measurements. The CD measurements indicated a partially ordered secondary structure of the protein in the multilayer, in contrast to i ts random coil configuration in the bulk. X-Ray reflectivity measureme nts revealed vertically well ordered multilayers with the protein loca ted within well defined slabs between the lipid headgroups of the indi vidual bilayers of the samples. These slabs consisted of protein, lipi d headgroup moieties, ions, and water molecules, each of which is of i mportance for the molecular organization of the multilamellar stacks. By combining X-ray and neutron reflectivity techniques and by in-situ exchange of the H2O by D2O within the multilayers, the presence of wat er within the protein slab was proven and its amount was estimated. Th e results demonstrate, that, under controlled environmental conditions , the organization of the proteo-lipid multilayers at the planar inter face can be elucidated to detail. Hence, the supported MBP membranes i nvestigated here can serve as valuable model systems for the natural m yelin sheath. (C) 1998 Elsevier Science S.A. All rights reserved.