Tilley L, Sawyer W H, Morrison J R, Fidge N H
Russell Grimwade School of Biochemistry, University of Melbourne, Parkville, Victoria, Australia.
J Biol Chem. 1988 Nov 25;263(33):17541-7.
Time-resolved phosphorescence anisotropy has been used to assess the rotational dynamics of human serum lipoproteins labeled with phosphorescent probes of high triplet yield. Labeling the lipid phase of low density, very low density, and high density lipoproteins with an eosinyl fatty acid revealed the existence of two motions. The shorter time constant was attributed to motion of the chromophore within the lipoprotein particle, while the longer time constant represented the global tumbling of the particles in solution. The measured correlation times for this global motion were about twice those predicted from the Stokes-Einstein relationship. Covalent labeling of the apolipoproteins of the low and high density lipoproteins with erythrosin revealed the existence of segmental motion of labeled domains of the apolipoprotein within their respective particles. The correlation times for this motion were within the range 10-50 microseconds. The binding of low density lipoproteins to receptors on membranes isolated from the adrenal cortex resulted in a freezing of the global motion, but maintenance of the faster segmental motion of the labeled domains of the apolipoprotein. The experiments imply that in these membranes there is no global motion of the low density lipoprotein-receptor complex on the phosphorescence time scale. Similar results were found for the binding of high density lipoproteins to liver plasma membranes. The contributions of nonspecific binding of the labeled lipoproteins to the measured phosphorescence anisotropy were carefully assessed.
时间分辨磷光各向异性已被用于评估用高三重态产率的磷光探针标记的人血清脂蛋白的旋转动力学。用曙红基脂肪酸标记低密度、极低密度和高密度脂蛋白的脂质相，揭示了两种运动的存在。较短的时间常数归因于发色团在脂蛋白颗粒内的运动，而较长的时间常数代表颗粒在溶液中的整体翻滚。测量到的这种整体运动的相关时间约为根据斯托克斯 - 爱因斯坦关系预测值的两倍。用赤藓红对低密度和高密度脂蛋白的载脂蛋白进行共价标记，揭示了载脂蛋白标记结构域在其各自颗粒内存在片段运动。这种运动的相关时间在10 - 50微秒范围内。低密度脂蛋白与从肾上腺皮质分离的膜上的受体结合导致整体运动冻结，但载脂蛋白标记结构域的较快片段运动得以维持。这些实验表明，在这些膜上，在磷光时间尺度上低密度脂蛋白 - 受体复合物没有整体运动。对于高密度脂蛋白与肝细胞膜的结合也发现了类似结果。仔细评估了标记脂蛋白的非特异性结合对测量的磷光各向异性的贡献。
