Molecular organization of cholesterol in polyunsaturated phospholipid membranes: a solid state H-2 NMR investigation

We compared the molecular organization of equimolar [3 alpha-H-2(1)]cholest erol in 18:0-18:1PC (1-stearoyl-2- oleoylphosphatidylcholine), 18:0-22:6PC (1-stearoyl-2-docosahexaenoylphosphatidylcholine), 18:0-20:4PC (1-stearoyl- 2-arachidonylphosphatidylcholine) and 20:4-20:4PC (1,2-diarachidonylphospha tidylcholine) bilayers by solid state H-2 NMR. Essentially identical quadru polar splittings (Delta nu(r) = 45 +/- 1 kHz) corresponding to the same mol ecular orientation characterized by tilt angle alpha(0) = 16 +/- 1 degrees were measured in 18:0-18:1PC, 18:0-22:6PC and 18:0-20:4PC. A profound diffe rence in molecular interaction with dipolyunsaturated 20:4-20:4PC, in contr ast, is indicated for the sterol. Specifically, the tilt angle alpha(0) = 2 2 +/- 1 degrees (derived from Delta nu(r) = 37 +/- 1 kHz) is greater and it s membrane intercalation is only 15 mol%. (C) 1999 Federation of European B iochemical Societies.