Cheng K H, Chen S Y, Butko P, Van der Meer B W, Somerharju P
Department of Physics, Texas Tech University, Lubbock 79409.
Biophys Chem. 1991 Feb;39(2):137-44.
The rates of intramolecular excimer formation of di(1'-pyrenemyristoyl)phosphatidylcholine (dipyPC) in dioleoylphosphatidyl-ethanolamine (DOPE), egg PE/diolein (DG) and dilinoleoyl-PE (DLPE)/1-palmitoyl-2-oleoyl-PC (POPC) were studied at different temperatures and lipid compositions. Both the excimer-to-monomer intensity ratio and the excimer association rate constant were employed to quantify the rate of excimer formation. The latter was calculated from the measured monomer fluorescence lifetime of dipyPC. We observed that the rate of excimer formation was sensitive to either the temperature-induced or lipid composition-induced lamellar-to-inverted hexagonal phase transition of the above lipid systems. As the lipids entered the inverted hexagonal phase, the rate of excimer formation increased at the temperature-induced phase transition for DOPE, but decreased at the composition-induced phase transition for both TPE/DG and DLPE/POPC systems by increasing the DG% and decreasing the PC%, respectively. We conclude that the rate of intramolecular excimer formation of dipyPC in the non-lamellar phase is influenced both by the intra-lipid free volume of the hydrocarbon region and the intra-rotational dynamics of the two lipid acyl chains.
在不同温度和脂质组成条件下，研究了二（1'-芘十四酰基）磷脂酰胆碱（dipyPC）在二油酰磷脂酰乙醇胺（DOPE）、鸡蛋磷脂酰乙醇胺/二油精（DG）和二亚油酰磷脂酰乙醇胺（DLPE）/1-棕榈酰-2-油酰磷脂酰胆碱（POPC）中的分子内激基缔合物形成速率。激基缔合物与单体强度比和激基缔合速率常数均用于量化激基缔合物形成速率。后者由测量得到的dipyPC单体荧光寿命计算得出。我们观察到，激基缔合物形成速率对上述脂质体系中温度诱导或脂质组成诱导的层状相向反相六角相转变敏感。当脂质进入反相六角相时，在DOPE的温度诱导相转变过程中，激基缔合物形成速率增加，但在TPE/DG和DLPE/POPC体系的组成诱导相转变过程中，分别通过增加DG%和降低PC%，激基缔合物形成速率降低。我们得出结论，非层状相中dipyPC的分子内激基缔合物形成速率受烃区域内脂质自由体积和两条脂质酰基链的内旋转动力学影响。
