Salamon Zdzislaw, Tollin Gordon
Department of Biochemistry and Molecular Biophysics, University of Arizona, Tucson, Arizona, USA.
Biophys J. 2004 Apr;86(4):2508-16. doi: 10.1016/S0006-3495(04)74306-4.
Plasmon-waveguide resonance spectroscopy is a recently developed optical method that allows characterization of mass and structural changes in two-dimensionally ordered thin films (e.g., proteolipid membranes) deposited onto a sensor surface. Full analysis of these systems involves fitting theoretical curves (obtained using Maxwell's equations) to experimental spectra measured using s- and p-polarized excitation. This allows values to be obtained for refractive indices and optical extinction coefficients in these two directions, as well as a value for film thickness, thereby providing information about mass density and anisotropy changes. This is a time-consuming process that works well for simple systems in which only a single conformational event occurs, but cannot distinguish between events involving multiple conformations that proceed either sequentially or in a parallel series of events. This article describes a graphical method that can distinguish between mass density and anisotropy changes in a simpler, more rapid procedure, even for processes that proceed via multiple conformational events. This involves measurement of plasmon-waveguide resonance spectral shifts obtained upon molecular interactions occurring in deposited films with both s- and p-polarized excitation, and transforming these from an (s-p) coordinate system into a (mass-structure) coordinate system. This procedure is illustrated by data obtained upon the binding of a small peptide, penetratin, to solid-supported lipid bilayer membranes.
表面等离子体波导共振光谱法是一种最近开发的光学方法，可用于表征沉积在传感器表面的二维有序薄膜（如蛋白脂质膜）的质量和结构变化。对这些系统进行全面分析需要将理论曲线（通过麦克斯韦方程组获得）与使用s偏振和p偏振激发测量的实验光谱进行拟合。这样可以得到这两个方向上的折射率和光学消光系数值，以及膜厚度值，从而提供有关质量密度和各向异性变化的信息。这是一个耗时的过程，对于仅发生单个构象事件的简单系统效果良好，但无法区分涉及多个构象的事件，这些事件可能按顺序发生，也可能以平行系列的方式发生。本文介绍了一种图形方法，即使对于通过多个构象事件进行的过程，也能以更简单、更快速的程序区分质量密度和各向异性变化。这涉及测量在沉积薄膜中发生分子相互作用时，使用s偏振和p偏振激发所获得的表面等离子体波导共振光谱位移，并将这些位移从（s-p）坐标系转换为（质量-结构）坐标系。通过小肽穿膜肽与固体支持脂质双层膜结合所获得的数据说明了这一过程。
