Thermotropic and mixing behavior of mixed-chain phosphatidylcholines with molecular weights identical with that of L-alpha-dipalmitoylphosphatidylcholine.

摘要: The thermotropic phase behavior of 10 mixed-chain phosphatidylcholines, in excess water, has been examined and compared with that identical-chain C(16):C(16)PC by using high-resolution differential scanning calorimetry (DSC). molecular weights (MW) these 11 species are the same, but their delta C/CL values, or normalized chain length differences, vary considerably, ranging from 0.035 to 0.540. thermodynamic parameters (Tm, H, S) associated main transitions for lipid dispersions exhibit biphasic V-shaped curves, when plotted against C/CL. Similar characteristic curves have reported previously aqueous phosphatidylcholines MW identical C(17):C(17)PC [Lin et al. (1990) Biochemistry 29, 7063-7072]. initial decrease Tm (delta H increasing values is attributed progressive increase magnitude chain-terminal perturbations on conformational statistics adjacent hydrocarbon chains hence lateral chain-chain interactions gel-state bilayer. At approximately equal 0.42, chain-end perturbation presumably at its maximum; beyond this point, highly asymmetric proposed pack, T less than Tm, into mixed interdigitated In new packing mode, methyl ends longer acyl relocated interfaces between core bilayer medium. This disposition bulky releases a certain degree disorders, leading an C/CL.(ABSTRACT TRUNCATED AT 250 WORDS)