FROZEN SOLUTION & VECTORIALLY ORIENTED SINGLE MONOLAYER OF MEMBRANE HEME PROTEIN

极大地改进了极化的Fe-EXAFS数据 共价冷冻水合单层酵母细胞色素c 被拴在混合CH3/-SH(6：1)端基的非极性表面 自组装单分子膜(SAM)化学吸附在硅衬底上。 利用计算的EXAFS光谱对这些数据进行了分析 使用FEFF7和a)5A内的本地原子环境 酵母细胞色素c晶体结构中的铁原子 血红素平面和单层平面之间的夹角或b) 时间平均的铁原子5A范围内的煤原子环境 在1纳秒分子动力学的最后300皮秒内 水合系留细胞色素c/sam体系的计算机模拟。 这两种方法都提供了血红素平面和 单层平面与独立的结果符合良好 血红素基团电子跃迁的光学线性二色性 而第二种方法最好地考虑了 实验极化EXAFS数据--即k(A-1)中的两个峰位置 手动峰形状，而不是主要的峰位置？考查 由周期采样计算的非极化EXAFS光谱 H？即每50皮秒？发生的瞬时构型 悬停1纳秒分子动力学模拟表明 铁原子特性的5A范围内的局域原子环境 酵母细胞色素冻融各向同性水溶液 C H重复出现，但在模拟水化的情况下很少发生 系留细胞色素c/SAM系统。

Greatly improved polarized Fe-EXAFS data have been obtained from frozen-hydrated single monolayers of yeast cytochrome c covalently tethered to the nonpolar surface of mixed-CH3/-SH (6:1) endgroup Self-Assembled Monolayers (SAM) chemisorbed onto silicon substrates. These data have been analyzed utilizing the EXAFS spectra calculated using FEFF7 and either a) the local atomic environment within 5A of the Fe-atom in the yeast cytochrome c crystal structure as a function of the angle between the heme plane and the monolayer plane or b) the lcoal atomic environment within 5A of the Fe-atom as time-averaged over the last 300 picoseconds of a 1 nanosecond Molecular Dynamics computer simulation of the hydrated tethered cytochrome c/SAM system. Both approaches provide an angle between the heme plane and the monolayer plane in good agreement with independent results from the optical linear dichroism of the heme groups electronic transitions while the second approach best accounts for all of the features of the experimental polarized EXAFS data ?i.e. both peak positions in k (A-1) Hand peak shapes as opposed to primarily peak positions?. Examination Hof the unpolarized EXAFS spectra calculated from periodically sampled H?i.e., every 50 picoseconds? instantaneous configurations occurring Hover the 1 nanosecond Molecular Dynamics simulation indicated that the Hlocal atomic environment within 5A of the Fe-atom characteristic of Hthe frozen-hydrated isotropic aqueous solution of yeast cytochrome c Hoccurs repeatedly, but infrequently within the simulated hydrated Htethered cytochrome c/SAM system.