SPECTROSCOPY OF AN ENGINEERED PURPLE CU(A) CENTER IN AZURIN

紫铜(A)中心的光谱表征 从铜绿假单胞菌中提取蓝铜蛋白天青素 (以下称为紫铜(A)天青。两者都是电喷雾 质谱学和铜分析表明该蛋白质结合了两个 每种蛋白质中的铜离子。电子吸收(UV-Vis)，磁性 圆二色(MCS)、多频电子顺磁 紫色的共振(EPR)和X射线吸收(XAS)光谱 铜(A)天青与其他天然或工程制造的天青惊人地相似 Cu(A)中心，表示它们都有相似的几何和 电子结构。多频EPR谱显示 G(平行)中分辨良好的七线超精细结构 区域，典型的离域混合价[Cu(1.5)？Cu(1.5)] 双核中心。与其他离域混价铜(A)的比较 中心，这个紫色的铜(A)天青具有相对较高的近红外能量 CuBCu770 nm吸收峰，最大吸收峰A(平行L)a t 55G； 最短的CuBCu距离为2.39A。这些结果可能反映了更多 天青中的空间压缩的铜(A)中心，可能是由于 迫使天青中通常的单核蓝铜中心 接受双核铜(A)中心，并与一般的 Cu2[SR]2的近红外吸收与Cu2[SR]2的变化趋势 核心收缩。

Spectroscopic characterization of a purple Cu(A) center engineered into the blue copper protein azurin from Pseudomonas aeruginosa (called purple Cu(A) azurin hereafter is presented. Both electrospray mass spectrometry and copper analysis indicated the protein binds two copper ions per protein. The electronic absorption (UV-vis), magnetic circular dichroism (MCS), multifrequency electron paramagnetic resonance (EPR), and X-ray absorption (XAS) spectra of the purple Cu(A) azurin are strikingly similar to other native or engineered Cu(A) center, indicating that they all share similar geometric and electronic structures. Multifrequency EPR spectra show a well-resolved seven-line hyperfine structure in the g(parallel) region, typical of a delocalized mixed-valence [Cu(1.5)???Cu(1.5)] binuclear center. Compared with other delocalized mixed-valence Cu(A) centers, this purple Cu(A) azurin has a relatively high energy near-IR CuBCu absorption at 770nm, the largest A(paralle l) a t 55 G, and the shortest CuBCu distance at 2.39A. These results may reflect a more sterically compressed Cu(A) center in azurin, perhaps as the result of forcing the normally mononuclear blue copper center in azurin to accept a binuclear Cu(A) center, and are consistent with the general trend between the near-IR CuBCu absorption and the degree of Cu2[SR]2 core contraction.