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Conformation‐dependent Raman bands of phospholipid surfaces. 3 —head group Ortho ‐phosphate stretching vibrations
Author(s) -
BicknellBrown Ellen,
Brown Kenneth G.,
Person Willis B.
Publication year - 1982
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.1250120218
Subject(s) - raman spectroscopy , conformational isomerism , chemistry , dihedral angle , crystallography , phospholipid , phosphate , molecular vibration , stereochemistry , hydrogen bond , molecule , organic chemistry , physics , biochemistry , membrane , optics
Vibrational frequencies of diethyl phosphate were calculated for rotamers for which the dihedral angle about the PO and CO bonds varied. The frequencies predicted for the symmetric and antisymmetric OPO stretches, the symmetric and antisymmetric ionic PO 2 − stretches, and the CC stretches are found to be sensitive to the PO and CO dihedral angles. The results of Raman temperature and solvent studies of diethyl phosphate are reported and are found to be in good agreement with the conclusions obtained from the normal coordinate analyses. Frequencies of diethyl phosphate rotamers having the geometries of crystalline glycerophosphorylcholine (GPC), crystalline GPC CdCCl 2 , and amorphous GPC CdCl 2 were calculated and compared to the Raman spectra of these phospholipid head group models. The normal coordinate analyses are in good agreement with Raman spectra. These results indicate that the observed frequencies of phosphate group vibrations may be compared to the normal coordinate analyses of diethyl phosphate rotamers to monitor conformation in phospholipid head groups (and other organic ortho ‐phosphates). The Raman symmetric OPO stretch bandwidth may be used to monitor rotational freedom or broadening due to the distribution of differing conformations.