Bussell S J, Koch D L, Hammer D A
School of Chemical Engineering, Cornell University, Ithaca, New York 14853, USA.
Biophys J. 1995 May;68(5):1828-35. doi: 10.1016/S0006-3495(95)80359-0.
A persistent discrepancy exists between theoretical predictions and experimental observations for the diffusion coefficients of integral membrane proteins in lipid bilayers free of immobilized proteins. Current thermodynamic theories overestimate tracer diffusion coefficients at high area fractions. We explore the hypothesis that the combined effect of hydrodynamic and thermodynamic interactions reconciles theory with experiment. We have determined previously the short- and long-time tracer diffusivities, Ds and Dl, respectively, of integral membrane proteins in lipid bilayers as a function of their area fraction, phi. The results are based on two-particle hydrodynamic and thermodynamic interactions and are precise to O(phi). Here we extend the results for Dl to high phi by combining the hydrodynamic results for Ds into theories for Dl based on many-particle thermodynamic interactions. The results compare favorably with the experimental measurements of Dl as a function of protein area fraction for bacteriorhodopsin in reconstituted membranes and for complex III of the mitochondrial inner membrane. The agreement suggests that both hydrodynamic and thermodynamic interactions are important determinants of diffusion coefficients of proteins in lipid bilayers. Additional experiments are required to verify the role of hydrodynamic interactions in protein diffusion in reconstituted systems.
对于没有固定化蛋白质的脂质双层中整合膜蛋白的扩散系数，理论预测与实验观测之间一直存在差异。当前的热力学理论在高面积分数时高估了示踪剂扩散系数。我们探讨了流体动力学和热力学相互作用的综合效应使理论与实验相符的假设。我们之前已经确定了脂质双层中整合膜蛋白的示踪剂扩散率，分别为短时间扩散率Ds和长时间扩散率Dl，它们是面积分数phi的函数。结果基于双粒子流体动力学和热力学相互作用，精确到O(phi)。在这里，我们通过将Ds的流体动力学结果纳入基于多粒子热力学相互作用的Dl理论中，将Dl的结果扩展到高phi。对于重组膜中的细菌视紫红质以及线粒体内膜的复合物III，结果与作为蛋白质面积分数函数的Dl实验测量结果进行了良好的比较。这种一致性表明，流体动力学和热力学相互作用都是脂质双层中蛋白质扩散系数的重要决定因素。需要额外的实验来验证流体动力学相互作用在重组系统中蛋白质扩散中的作用。
