Microdomain formation in phosphatidylethanolamine bilayers detected by H-2NMR

In deuterium NMR spectra of phosphatidylethanolamine bilayers with an extre mely high content of saturated fatty acids, each C1 deuteron of the glycero l backbone gave rise to a doublet.(1) This suggests the presence of two bac kbone conformations, the exchange between which is slow on an NMR time scal e. The origin of the two conformations has been investigated in this work u sing saturated 1,2-diacyl-sn-glycero-3-phosphoethanolamine specifically deu terated in the glycerol backbone. The results showed that the two conformat ions originate from different domains, which have different fatty acid comp ositions. The differential scanning calorimetry of the bilayers suggested t hat the size of the domain is not large enough to show an independent phase transition. Thus, the formation of microdomains in the phosphatidylethanol amine bilayers has been concluded. Conformational difference in different d omains was shown to be restricted to the C1 position of the glycerol backbo ne. The microdomains of phosphatidylethanolamine were retained even in the presence of other phospholipids.