Scarlata S F
Cornell University Medical College, College of Medicine, New York 10021.
Biophys J. 1989 Jun;55(6):1215-23. doi: 10.1016/S0006-3495(89)82917-0.
The thermal coefficient of the frictional resistance to fluorophore rotation (b), a parameter related to the change in the local viscosity with temperature, was determined for anthroyloxy-fatty acid probes in micelles and dimyristoyl lecithin (DMPC) and dioleoyl lecithin (DOPC) unilamellar and multilamellar vesicles. The value of b and the percent change in anisotropy with temperature (%dA/dT) remained constant with membrane depth and only depended on composition. These parameters were also the same when either in-plane, or in-plane and out-of-plane fluorophore motions were observed. This result indicates that the membranes expand isotropically. The magnitude of b was found to be primarily dependent on the packing of the hydrocarbon chains with higher b values relating to more closely-packed chains. b was responsive to the gel to liquid crystal phase transition of DMPC and the bilayer to hexagonal phase transition of egg-phosphatidylethanolamine. When the enthalpy values for the fluorophore transfer from one phase to another are calculated, the values are larger than those measured by calorimetry and reflect a discrepancy between the microscopic enthalpy experienced by the fluorophore due to a change in environment versus the macroscopic enthalpy of the system as a whole.
测定了胶束以及二肉豆蔻酰卵磷脂（DMPC）和二油酰卵磷脂（DOPC）单层和多层囊泡中蒽氧基脂肪酸探针的荧光团旋转摩擦阻力的热系数（b），该参数与局部粘度随温度的变化有关。b值以及各向异性随温度的百分比变化（%dA/dT）随膜深度保持恒定，且仅取决于组成。当观察到荧光团的面内或面内和面外运动时，这些参数也是相同的。这一结果表明膜是各向同性膨胀的。发现b的大小主要取决于烃链的堆积情况，较高的b值与堆积更紧密的链相关。b对DMPC的凝胶态到液晶态转变以及蛋黄磷脂酰乙醇胺的双层态到六方相转变有响应。当计算荧光团从一个相转移到另一个相的焓值时，这些值大于量热法测得的值，反映出荧光团由于环境变化所经历的微观焓与整个系统的宏观焓之间存在差异。
