Assembly of purple membranes on polyelectrolyte films.
Assembly of purple membranes on polyelectrolyte films.
复制标题
在聚电解质膜上组装紫色膜。
作者：
Marie;E. Estephan;T. Cloitre;R. Legros;F. Cuisinier;L. Zimányi;C. Gergely
的膜蛋白细菌视紫红质在其天然的膜结合形式（紫色膜）被吸附，并纳入到多层膜，和吸附原位监测光波导光模式光谱。当吸附在带负电或带正电的表面上时，分别观察到单层或双层紫色膜的形成。原子力显微镜图像也证明了吸附在多层膜上的紫色膜补丁。通过改变溶液的离子强度以及紫膜浓度来评价吸附过程的驱动力。在高的紫膜浓度，互穿的双链环可能提供新的结合位点的第二层的紫膜的吸附，而在较低的浓度下，只有一个单一的层形成。负表面不促进第二蛋白质层吸附。除了静电力之外的驱动力，如疏水力，应该在紫色/紫色膜分层中发挥作用。所有这些因素的微妙的相互作用决定了紫膜/紫膜基质的形成，其中掺入的紫膜具有推测的高度取向，其细胞质或细胞外侧分别朝向带负电荷或正电荷的膜上的主体。采用衰减全反射傅里叶变换红外光谱法研究了细菌视紫红质在表面吸附和掺入多层膜过程中的结构稳定性。吸附和掺入的紫色膜内的多层膜不干扰的构象大多数膜嵌入的α-螺旋结构的蛋白质，但可能会稍微改变的膜外段的结构或它们与环境的相互作用。这种高稳定性与许多球状蛋白质吸附到表面时主要是β折叠结构的较低稳定性不同。
The membrane protein bacteriorhodopsin in its native membrane bound form (purple membrane) was adsorbed and incorporated into polyelectrolyte multilayered films, and adsorption was in situ monitored by optical waveguide light-mode spectroscopy. The formation of a single layer or a double layer of purple membranes was observed when adsorbed on negatively or positively charged surfaces, respectively. The purple membrane patches adsorbed on the polyelectrolyte multilayers were also evidenced by atomic force microscopy images. The driving forces of the adsorption process were evaluated by varying the ionic strength of the solution as well as the purple membrane concentration. At high purple membrane concentration, interpenetrating polyelectrolyte loops might provide new binding sites for the adsorption of a second layer of purple membranes, whereas at lower concentrations only a single layer is formed. Negative surfaces do not promote a second protein layer adsorption. Driving forces other than just electrostatic ones, such as hydrophobic forces, should play a role in the polyelectrolyte/purple membrane layering. The subtle interplay of all these factors determines the formation of the polyelectrolyte/purple membrane matrix with a presumably high degree of orientation for the incorporated purple membranes, with their cytoplasmic, or extracellular side toward the bulk on negatively or positively charged polyelectrolyte, respectively. The structural stability of bacteriorhodopsin during adsorption onto the surface and incorporation into the polyelectrolyte multilayers was investigated by Fourier transform infrared spectroscopy in attenuated total reflection mode. Adsorption and incorporation of purple membranes within polyelectrolyte multilayers does not disturb the conformational majority of membrane-embedded alpha-helix structures of the protein, but may slightly alter the structure of the extramembraneous segments or their interaction with the environment. This high stability is different from the lower stability of the predominantly beta-sheet structures of numerous globular proteins when adsorbed onto surfaces.