METASTABILITY OF DIMIRISTOYLPHOSPHATIDYLETHANOLAMINE AS STUDIED BY FT-IR AND THE EFFECT OF ALPHA-TOCOPHEROL

The metastability of dimiristoylphosphatidylethanolamine (DMPE) has be en studied by means of Fourier transform infrared spectroscopy (FT-IR) , both in the absence and in the presence of alpha-tocopherol. Two dif ferent methods of hydration were used to prepare the samples, poorly h ydrated and well hydrated, and the results have been compared with anh ydrous DMPE. Poorly hydrated DMPE gave place to a high-melting phase f ormed upon melting from gel to L(alpha) at approx. 49 degrees C, with a new transition to L(alpha) at approx. 55 degrees C. However, well hy drated DMPE incubated at 4 degrees C for 49 days gave place to a subge l phase which was transformed by heating into a L(beta) phase at about 40 degrees C and this into a L(alpha) phase after further heating at 52 degrees C. The subgel phase was more hydrated and less rigid than t he high-melting phase, On the other hand, alpha-tocopherol, when inclu ded in poorly hydrated DMPE, stabilized a high-melting phase, which wa s transformed by heating, directly into a L(alpha) phase. However, whe n a sample of DMPE containing alpha-tocopherol was incubated for 49 da ys at 4 degrees C a dehydrated solid phase different from the subgel a nd the high-melting phases was formed.