Distance measurements and conformational analysis of sn-2- arachidonoylglycerol-membrane sample by H-P REDOR NMR

The purpose of these studies is to determine the intermolecular distances that define the location, orientation, and conformation of 2-AG in palmitoyl-oleoyl-phosphatidylcholine (POPC) lipid bilayers using rotational-echo double-resonance (REDOR) NMR. All five protons on the glycerol backbone of 2-AG were replaced with H and the distance between the deuterons and naturally occurring P on the POPC lipid headgroup determined with REDOR. To determine the distance from each deuteron to the phosphorus, the POPC headgroup was arranged in a hexagonal array. The 2-AG intercalates between the lipid molecules and the H labels, resulting in an average distance of z directly above or below the center of the parallelogram of the four phosphorus atoms P, P, P, and P. For different z values, the H-P inter-nuclear distances were 7.6-9.1 Å (H-P and H-P) and 4.4-6.7 Å ( H-P and H-P ). Each result involved the calculations and summation of 893,101 terms. Based on the curve-fitting parameters, the calculations with z = 0 fits the data the best, which means these methylene H atoms are at the same level as the phosphate group of the POPC lipid bilayer. Molecular dynamic simulation data suggested that the H atoms at the glycerol backbone of 2-AG are involved in an extended H-bonding network with the phosphorus atoms after 10-ns simulation. © 2014 Springer Science+Business Media.