Deuteron NMR Study of Molecular Mobility in a Polymer Model Membrane

Wiley - Tập 89 Số 11 - Trang 1208-1214 - 1985
Rainer Ebelhäuser1, Hans Wolfgang Spieß1
1Max-Planck-Institut für Polymerforschung, Postfach 3148, D-6500 Mainz, Federal Republic of Germany

Tóm tắt

AbstractThe molecular mobility of a polymer model membrane is studied by 2H NMR. The lipid analogue consists of a quaternary ammonium ion, to which a methacryloylic moiety is attached via a spacer to the hydrophilic head group. A methylene group of the spacer, the methyl‐head group and methylene groups in the 1‐, 2‐, and 7‐position of the lipid chains are selectively deuterated. Temperature dependent 2H NMR spectra are reported for both, the monomer and the polymer membrane below and above the main phase transition. The data are quantitatively analyzed in terms of a simple motional model, in which the complex molecular dynamics is approximated by a six‐site jump model describing rotations about the long axis of the molecule and conformational changes. The increasing mobility with increasing temperature is only in part due to an increase of the jump rate between different sites. It also reflects the increase in the number of conformations accessible. As a quantitative measure of the mobility at a given site, a mean jump frequency is extracted from the data. For the monomer Ω˜ and its temperature dependence in the liquid crystalline phase is almost independent of the site being studied. In the polymer, however, major differences are observed, Ω˜ for the head group and the 7‐position of the lipid chain differing by two orders of magnitude. The mobility of the spacer is even lower. This 2H NMR study thus shows that although the polymerization largely hinders the head group mobility, the chain flexibility most important for membrane applications is retained.

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Thông tin
Thông tin xuất bản

Wiley

Tập 89 Số 11

1208-1214

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