Probing the gel to liquid-crystalline phase transition and relevant conformation changes in liposomes by C-13 magic-angle spinning NMR spectroscopy

摘要

A straightforward way to visualize gel to liquid-crystalline phase transition in phospholipid membranes is presented by using C-13 magic-angle spinning NMR. The changes in the C-13 isotropic chemical shifts with increasing temperature are shown to be a sensitive probe of the main thermotropic phase transition related to lipid hydrocarbon chain dynamics and relevant conformational changes. The average value of the energy difference between trans and gauche states in the central C4-11 fragment of the DMPC acyl chain was estimated to be 4.02 +/- 0.2 kJ mol(-1) in the liquid crystalline phase. The reported spectral features will be useful in C-13 solid state NMR studies for direct monitoring of the effective lipid chain melting allowing rapid uniaxial rotation of membrane proteins in the biologically relevant liquid-crystalline phase. (C) 2015 Elsevier B.V. All rights reserved.