Raman spectra and conformation of the glycerophosphorylcholine headgroup.

Abstract The Raman and infrared spectra of L-α-glycerophosphylcholine (GPC) and its cadmium complex (GPC·CdCl2) have been measured for both the anhydrous and hydrate crystals. The Raman spectra of GPC and GPC·CdCl2 dissolved in water are also reported. All the spectra fall into three distinctive patterns, demonstrating the existence of at least three different kinds of rotational isomers; the first is stable in the anhydrous GPC crystal, the second is stable in the GPC hydrate and GPC·CdCl2 hydrate crystals and the third is stable in the anhydrous GPC·CdCl2 crystal and also in aqueous solutions of GPC·CdCl2. The latter form is reported for the first time. Raman spectra of dimyristoyl-L-α-phosphatidylcholine (L-DMPC) and dipalmitoyl-(L and DL)-α-phosphatidylcholine (L and DL-DPPC) hydrates have been measured below, around and above the transition temperature T1. The spectra below T1 indicate that the conformation of the glycerophosphorylcholine (GPC) headgroup in the L-DMPC crystal is similar to that in the L-DPPC crystal. The headgroup conformation in the DL-DPPC crystal is quite different from that in the L-DPPC crystal, although they became the same aftera crystalline trasnformation of DL-DPPC. The changes of the Raman spectra through the T1 transition for the above crystals show that the headgroup conformation remains unchanged at the beginning o the transition.