EFFECTS OF ANISODAMINE ON THE PHASE-BEHAVIOR OF DPPG DMPC BINARY-MIXTURES/

Fluorescence polarization of n-(9-anthroyloxyl)-stearic acid (n-AS), 1 6-(9-anthroyloxyl)-palmitic acid (16AP) and differential scanning calo rimetry (DSC) experiments have been carried out to examine the influen ce of anisodamine on the phase behavior of dipalmitoylphosphatidylglyc erol (DPPG)/dimyristoylphosphatidylcholine (DMPC) binary mixtures. The experiments of fluorescence polarization indicated that the bilamella r vesicles of non-interdigitated DPPG/DMPC systems showed clear polari zation gradient in the acyl chains. In DPPG/DMPC systems with 3 mM ani sodamine, when the molar ratio of DMPC was below 50%, the normal polar ization gradient almost disappeared, the interdigitation of fatty acid chains occurred with the end carbon groups inserting into the opposit e layer and reaching the level of 5C. When DMPC was above 60% however, the polarization gradient bf carbon chains reappeared, which suggeste d non-interdigitation. Results of DSC showed that in various DPPG/DMPC systems, T-m and Delta H decreased with the increase of DMPC concentr ation. The DPPG-DMPC phase diagram, derived from calorimetric data, ex hibited the compatibility of DPPG and DMPC although DMPC tended to pre vent the mixtures from forming interdigitated structure in the gel sta te. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.