Horton Margaret R, Reich Christian, Gast Alice P, Rädler Joachim O, Nickel Bert
Department für Physik, Ludwig-Maximilians-Universität, Geschwister-Scholl-Platz 1, 80539 München, Germany.
Langmuir. 2007 May 22;23(11):6263-9. doi: 10.1021/la063690e. Epub 2007 May 1.
We study proteins at the surface of bilayer membranes using streptavidin and avidin bound to biotinylated lipids in a supported lipid bilayer (SLB) at the solid-liquid interface. Using X-ray reflectivity and simultaneous fluorescence microscopy, we characterize the structure and fluidity of protein layers with varied relative surface coverages of crystalline and noncrystalline protein. With continuous bleaching, we measure a 10-15% decrease in the fluidity of the SLB after the full protein layer is formed. We propose that this reduction in lipid mobility is due to a small fraction (0.04) of immobilized lipids bound to the protein layer that create obstacles to membrane diffusion. Our X-ray reflectivity data show a 40 A thick layer of protein, and we resolve an 8 A layer separating the protein layer from the bilayer. We suggest that the separation provided by this water layer allows the underlying lipid bilayer to retain its fluidity and stability.
我们利用链霉亲和素和抗生物素蛋白（它们与固液界面处支撑脂质双层（SLB）中生物素化脂质结合）来研究双层膜表面的蛋白质。通过X射线反射率和同步荧光显微镜技术，我们表征了具有不同结晶和非结晶蛋白质相对表面覆盖率的蛋白质层的结构和流动性。通过连续漂白，我们测量到在完整蛋白质层形成后，SLB的流动性下降了10 - 15%。我们认为脂质流动性的这种降低是由于一小部分（0.04）与蛋白质层结合的固定化脂质造成的，这些脂质对膜扩散形成了障碍。我们的X射线反射率数据显示有一层40埃厚的蛋白质层，并且我们分辨出一层8埃厚的层将蛋白质层与双层膜分隔开。我们认为由这一水层提供的分隔使得下层脂质双层能够保持其流动性和稳定性。
