氧合钴肌红蛋白和氧合钴血红蛋白中双氧键合的共振拉曼光谱研究：结合的O--O伸缩振动分裂的结构含义
Resonance Raman investigation of dioxygen bonding in oxycobaltmyoglobin and oxycobalthemoglobin: structural implication of splittings of the bound O--O stretching vibration.
作者信息
Tsubaki M, Yu N T
出版信息
Proc Natl Acad Sci U S A. 1981 Jun;78(6):3581-5. doi: 10.1073/pnas.78.6.3581.
Splittings related to the stretching vibration of bound dioxygen in hemoproteins have been detected by resonance Raman spectroscopy. With excitation at 406.7 nm we observe three isotope-sensitive lines in oxycobaltmyoglobin (oxyCoMb) [or in oxycobalthemoglobin A (oxyCoHbA)] at 1103 (1107), 1137 (1137), and 1153 (1152) cm-1, of which the most intense one appears at 1137 cm-1. The first two frequencies arise from resonance interaction between a v(O--O) mode at approximately 1122 cm-1 and an accidentally degenerate porphyrin ring mode at 1123 (1121) cm-1, whereas the third one represents an "unperturbed" v(O--O) vibration from a different species. These two v(O--O) modes at approximately 1122 and approximately 1153 cm-1 shift to approximately 1066 and approximately 1096 cm-1, respectively, upon 16O2 leads to 18O2 substitution. The same resonance interaction may also occur in oxyFeMb (probably also in oxyFeHb(a), because it exhibits an intensity increase at 1125 cm-1 upon 16O2 leads to 18O2 substitution, although the v(O--O) vibrations have not been observed directly. Concomitant enhancement is observed in the v(Co--O) vibration at 539 (537( cm-1, which is considerably lower than the v(Fe--O) frequency at approximately 570 cm-1 in oxyFeMb and oxyFeHbA. The Co--O bond is longer and weaker than the Fe--O bond. Enhancement of both v(O--O) and v(Co--O) indicates the existence of a charge-transfer transition underlying the Soret band, which may be assigned as pi*(pi gO2/xz) leads to sigma(dz2Co/pi g*). The presence of two v(O--O) vibrations (at approximately 1122 and approximately 1152 cm-1) but only one v(Co--O) mode at approximately 538 cm-1) means that the two species in oxyCoMB or oxyCoHbA have the same Co--O bond lengths but different O--O bond lengths. The bound dioxygen in a bent end-on configuration may have two allowed orientations, which differ in the extent of sp2(N epsilon) leads to pi*(O2) donation from distal histidine.
通过共振拉曼光谱法已检测到与血红蛋白中结合双氧的伸缩振动相关的分裂。在406.7 nm激发下，我们在氧合钴肌红蛋白（oxyCoMb）[或氧合钴血红蛋白A（oxyCoHbA）]中观察到三条同位素敏感谱线，分别位于1103（1107）、1137（1137）和1153（1152）cm-1处，其中最强的一条出现在1137 cm-1处。前两个频率源于大约1122 cm-1处的v（O--O）模式与1123（1121）cm-1处意外简并的卟啉环模式之间的共振相互作用，而第三个频率代表来自不同物种的“未受扰动”的v（O--O）振动。当16O2被18O2取代时，这两个大约在1122和大约1153 cm-1处的v（O--O）模式分别移至大约1066和大约1096 cm-1处。相同的共振相互作用也可能发生在氧合铁肌红蛋白中（可能也在氧合铁血红蛋白（a）中，因为在16O2被18O2取代时，它在1125 cm-1处强度增加，尽管尚未直接观察到v（O--O）振动。同时，在539（537）cm-1处的v（Co--O）振动也被观察到增强，这比氧合铁肌红蛋白和氧合铁血红蛋白A中大约570 cm-1处的v（Fe--O）频率低得多。Co--O键比Fe--O键更长且更弱。v（O--O）和v（Co--O）的增强表明在Soret带下方存在电荷转移跃迁，其可能被指定为π*（πgO2/xz）→σ（dz2Co/πg*）。存在两个v（O--O）振动（大约在1122和大约1152 cm-1处）但只有一个大约在538 cm-1处的v（Co--O）模式意味着氧合钴肌红蛋白或氧合钴血红蛋白A中的两个物种具有相同的Co--O键长但不同的O--O键长。以弯曲端对端构型结合的双氧可能有两个允许的取向，它们在远端组氨酸向π*（O2）的sp2（Nε）→π*（O2）供体程度上有所不同。
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