Mazères S, Lagane B, Welby M, Trégou V, Lopez A
Institut de Pharmacologie et Biologie Structurale du CNRS, Toulouse, France.
Spectrochim Acta A Mol Biomol Spectrosc. 2001 Sep 14;57(11):2297-311. doi: 10.1016/s1386-1425(01)00486-3.
Phospholipids pyrene labeled are widely used to investigate dynamics and organizations of membranes. We studied pyrene probe lateral distribution by analyzing the variations of the molar absorption coefficient (epsilon) versus probe concentrations, in small unilamellar vesicles (SUV) made of phospholipids and/or glycolipids, with pyrene labeled phosphatidylcholine (PyPC) or phosphatidylglycerol (PyPG). The results were interpreted according to an infinite associative model. They indicated that an effective self-association process corresponding to K ranging from 30 to 100 M(-1) occurred with those probes incorporated in dimannosyl diacylglycerol (DMDG). In contrast, after SUV labeling of egg yolk phosphatidylcholine (EggPC) or phosphatidylglycerol (EggPG), K values < 1 M(-1) were determined. The corresponding percentages of various stacked forms of pyrene probes were calculated. They indicated that, for a 3% PyPG labeling, the monomer represented 21% of n-mers in DMDG and 94% in EggPC. The analysis of fluorescence experiments carried out on the same samples indicated that: (i) the fluorescence process of pyrene probes was generated by the monomers: and (ii) the excimer forming resulted from a diffusional encounter between one excited and one non-excited monomer. A correction of fluorescence data allowing a more correct interpretation of fluorescence measurements was proposed.
芘标记的磷脂被广泛用于研究膜的动力学和组织结构。我们通过分析摩尔吸收系数（ε）随探针浓度的变化，研究了芘探针在由磷脂和/或糖脂制成的小单层囊泡（SUV）中的横向分布，这些囊泡中含有芘标记的磷脂酰胆碱（PyPC）或磷脂酰甘油（PyPG）。结果根据无限缔合模型进行了解释。结果表明，当这些探针掺入二甘露糖基二酰基甘油（DMDG）中时，会发生有效自缔合过程，其平衡常数K范围为30至100 M⁻¹。相比之下，在用蛋黄磷脂酰胆碱（EggPC）或磷脂酰甘油（EggPG）对SUV进行标记后，测定的K值<1 M⁻¹。计算了芘探针各种堆积形式的相应百分比。结果表明，对于3%的PyPG标记，在DMDG中单体占n聚体的21%，在EggPC中占94%。对相同样品进行的荧光实验分析表明：（i）芘探针的荧光过程由单体产生；（ii）激基缔合物的形成是由一个激发单体与一个非激发单体之间的扩散碰撞导致的。提出了对荧光数据的校正方法，以便更正确地解释荧光测量结果。
