Sites of Photolytic Intermolecular Cross-Linking between Fatty Acyl Chains in Phospholipids Carrying a Photoactivable Carbene Precursor

Article abstract of DOI:10.1021/ja00378a036

A number of sn-glycero-3-phosphorylcholines containing the photosensitive ω-undecanoyl group in the sn-2 position and a dideuterated palmitic or stearic acid with both deuteriums on specific carbon atoms along the hydrocarbon chain in the sn-1 position were synthesized.Photolysis of either sonicated vesicles or multilamellar dispersions prepared from these synthetic phospholipids gave extensive intermolecularly cross-linked products.The distribution of the sites of cross-linking was determined by an analysis of cross-linked dimeric fatty esters by using low-resolution electron impact mass spectrometry.The predominance of the benzylic cleavage with a γ-hydrogen abstraction in the mass spectra of these diesters rendered such a quantitation relatively easy.Mass spectral analysis showed that there is a broad distribution in the cross-linking positions along the deuterated sn-1 chain, with the amount of cross-linking increasing toward the hydrophobic core of the bilayer.These results are in agreement with the conformational mobility of the fatty acyl chains and the localization of the photosensitive diazirinophenoxy group in the middle of the bilayer.