Theretz A, Teissie J, Tocanne J F
Eur J Biochem. 1984 Jul 2;142(1):113-9. doi: 10.1111/j.1432-1033.1984.tb08257.x.
Interactions between the antibiotic polymyxin B and monolayers of dipalmitoylglycerophosphoglycerol have been reinvestigated through a study of the structure and dynamics of the complexes by means of an interface fluorimeter of our fabrication. A fluorescence technique has been developed where the use of linearly polarized incident beams gives the simultaneous determination of the orientation and the lateral diffusion rate of a fluorescent probe inserted in the film. The present investigation was carried out with 12-(9-anthroyloxy)-stearic acid, a fluorescent compound which forms non-fluorescent photodimers upon illumination. Orientation of the probe was studied by computing the ratio of the two dimerization constants KD and the ratio of the fluorescence intensities obtained with crossed linearly polarized incident lights. The lateral diffusion rate of the probe was obtained by measuring fluorescence recovery after photobleaching (photodimerization) of the probe. Control experiments, carried out with dimyristoylglycerophosphocholine, a lipid which does not interact with polymyxin B, show that the antibiotic does not significantly modify the behaviour of the probe. Both in terms of orientation and dynamics, with respect to dipalmitoylglycerophosphoglycerol, when the antibiotic is present in the subphase (1 microM, saturating conditions), data indicate that the lipid remains in a liquid-expanded state. This is true even at a high surface pressure (pi approximately equal to 37 mN X m-1), above the apparent 'transition' which can be observed at 30-35 mN X m-1 on its compression isotherm. Computation of the contribution of polymyxin B to the film expansion to the conclusion that this 'transition' would be a structural transition between two models of interaction: one, below the 'transition', where the polypeptide ring penetrates between the film-forming lipid molecules and another one, above the 'transition', were the antibiotic is adsorbed at the lipid-water interface with only its hydrocarbon chain penetrating the film.
通过使用我们自制的界面荧光计研究复合物的结构和动力学，对抗生素多粘菌素B与二棕榈酰甘油磷酸甘油单层之间的相互作用进行了重新研究。已开发出一种荧光技术，利用线偏振入射光束可同时测定插入膜中的荧光探针的取向和横向扩散速率。本研究使用12-(9-蒽氧基)硬脂酸进行，这是一种荧光化合物，光照后会形成非荧光光二聚体。通过计算两个二聚化常数KD的比值以及用交叉线偏振入射光获得的荧光强度比值来研究探针的取向。通过测量探针光漂白（光二聚化）后的荧光恢复来获得探针的横向扩散速率。用与多粘菌素B不相互作用的脂质二肉豆蔻酰甘油磷酸胆碱进行的对照实验表明，该抗生素不会显著改变探针的行为。就取向和动力学而言，对于二棕榈酰甘油磷酸甘油，当抗生素存在于亚相中（1 microM，饱和条件）时，数据表明脂质保持在液体膨胀状态。即使在高表面压力（π约等于37 mN·m-1）下也是如此，该压力高于在其压缩等温线上30 - 35 mN·m-1处可观察到的表观“转变”。计算多粘菌素B对膜膨胀的贡献得出结论，这种“转变”将是两种相互作用模型之间的结构转变：一种是在“转变”以下，多肽环穿透成膜脂质分子之间；另一种是在“转变”以上，抗生素仅以其烃链穿透膜的方式吸附在脂质 - 水界面。
