EFFECT OF BETA-CAROTENE ON STRUCTURAL AND DYNAMIC PROPERTIES OF MODEL PHOSPHATIDYLCHOLINE MEMBRANES .2. A P-31-NMR AND C-13-NMR STUDY

Spin label EPR studies (Strzalka and Gruszecki (1994) Biochim. Biophys. Acta 1194, 138-142) revealed that beta-carotene affects structural and dynamic properties of model dipalmitoylphosphatidylcholine (DPPC) membranes (multilamellar liposomes) more than polar carotenoid lutein. NMR measurements presented in this paper demonstrate that beta-carotene exerts different effect on various groups of the DPPC molecule. It was found that beta-carotene: (1) increases motional freedom of lipid headgroups as revealed by means of P-31-NMR; (2) increases motional freedom of alkyl chains forming the hydrophobic core of the membrane greater than that of a choline moiety as revealed by means of C-13-NMR. In all cases the effect of beta-carotene with respect to the dynamics of DPPC molecules is found to be more pronounced below the main phase transition temperature than in the membrane's fluid state. The influence of beta-carotene on the molecular dynamics of DPPC molecules is discussed in terms of localization and orientation of this pigment within lipid bilayer.