ANISODAMINE CAUSES ACYL-CHAIN INTERDIGITATION IN PHOSPHATIDYLGLYCEROL

The effect of anisodamine on the structure of the gel phase and the pr operties of the acyl chain disordering transition of dipalmitoylphosph atidylglycerol (DPPG) has been studied through high-sensitivity differ ential scanning calorimetry (DSC) and fluorescence polarization measur ements of 16-(9-anthroyloxyl)-palmitic acid (16AP) and 3-(9-anthroylox yl)-stearic acid (3AS), labeling, respectively, the ends and the third carbon of the acyl chains. The non-interdigitated DPPG multilamellar vesicles formed in HEPES buffer show clear fluidity gradient in their acyl chains, whereas the fluidity gradients are completely abolished i n the presence of anisodamine. The DSC results showed that the phase t ransition temperature (T(m)) of DPPG is decreased and the enthalpy (DE LTAH) is increased by anisodamine, while the pre-transition vanishes. At 3 mM anisodamine, the DELTAH of DPPG reaches 9.6 kcal/mol. It can b e concluded that DPPG forms an interdigitated gel phase in the presenc e of anisodaminc. A molecular scheme for the interaction of anisodamin e with DPPG is proposed.