Glycerol backbone conformation in phosphatidylcholines is primarily determined by the intramolecular stacking of the vicinally arranged acyl chains

Abstract

To analyse the effect of the altered glycerol backbone structure on the glycerophospholipid conformation, we have replaced the glycerol moiety by the rac-1,2,4-butanetriol residue in 1,2-diacyl-sn-glycero-3-phosphocholines (PC), and then analysed the resulting 1,2-dialkanoyloxy-rac-but-4-yl-[2-(trimethylammonium)ethyl] phosphates (1,2-bPC) and 1,3-dialkanoyloxy-rac-but-4-yl-[2-(trimethylammonium)ethyl] phosphates (1,3-bPC) by high-resolution ¹H- and ¹³C-NMR spectroscopy in both CDCl₃ and D₂O. The preferred conformation about the C1-C2 glycerol bond in PC was almost completely preserved in 1,2-bPC, but it was completely random in case of 1,3-bPC. Out of the three C-C bonds present in the butanetriol backbone of 1,3-bPC, only the C2-C3 bond experienced a restricted rotation. However, the conformational preference about this bond was virtually similar to that observed for the C1-C2 bond in PC. These results clearly demonstrate that the preferred conformation of the glycerol backbone is determined primarily by the intramolecular acyl chain stacking which essentially requires a vicinal arrangement of the acyl chains in glycerophospholipids.