Understanding Sterol-Membrane Interactions,Part II:Complete 1H and ~(13)C Assignments by Solid-State NMR Spectroscopy and Determination of the Hydrogen-Bonding Partners of Cholesterol in a Lipid Bilayer

摘要

The complete assignment of cholesterol ~1H and ~(13)C NMR resonances in a lipid bilayer environment(L_alpha-dimyristoylphosphatidylcholine/choles-terol 2:1)has been obtained by a combination of ID and 2D MAS NMR experiments:~(13)C spectral editing,ge-HSQC,dipolar HETCOR and J-based HETCOR.Specific chemical shift variations have been observed for the Cl-C6 atoms of cholesterol measured in CC_(14)solution and in the membrane.Based on previous work(E Jolibois,O.Soubias,V.Real,A.Milon,Chem.Eur.J.2004,10,preceding paper in this issue:DOI:10.1002/chem.200400245)these variations were attributed to local changes around the cholesterol hydroxy group,such as the three major rotameric states of the C3-O3 bond and different hydrogen bonding partners(water molecules,carboxy and phosphodiester groups of phosphatidyl-choline).Comparison of the experimental and theoretical chemical shifts obtained from quantum-chemistry calculations of various transient molecular complexes has allowed the distributions of hydrogen bonding partners and hydroxy rotameric states to be determined.This is the first time that the probability of hydrogen bonding occurring between cholesterol's hydroxy group and phosphatidylcholine's phosphodiester has been determined experimentally.