Inhomogeneous broadening in spectral bands of carbonmonoxymyoglobin. The connection between spectral and functional heterogeneity.
Inhomogeneous broadening in spectral bands of carbonmonoxymyoglobin. The connection between spectral and functional heterogeneity.
复制标题
碳单氧肌红蛋白的光谱带不均匀展宽。
DOI：
10.1016/s0006-3495(90)82522-4
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发表时间：
1990
影响因子：
3.4
通讯作者：
Young,RD
中科院分区：
文献类型：
--
作者：
Ormos,P;Ansari,A;Braunstein,D;Cowen,BR;Frauenfelder,H;Hong,MK;Iben,IE;Sauke,TB;Steinbach,PJ;Young,RD
闪光光解后，CO 与肌红蛋白的重新结合动力学在低于约 180 K 的时间里呈非指数关系；动力学受焓垒的分布控制。这种分布是由蛋白质构象的不均匀性引起的，称为构象亚状态。 Soret 和 IR CO 拉伸带的烧孔实验测试了构象亚态的不均匀分布导致光谱不均匀展宽的假设。 CO 在 10 K 的索雷带中的不同波长下缓慢光解。索雷带和以 1,945 cm-1 为中心的 CO 拉伸带 A1 都在光解过程中发生移动，表明不同的波长会激发分布群体的不同部分。我们还通过测量 CO 分子重新结合时 Soret 和 A1 谱带的峰移进行了动力学烧孔实验。这些变化表明光谱和焓分布是相关的。在 A1 波段中，光谱和焓分布高度相关，而在 Soret 中相关性较弱。从光谱和动力学烧孔实验中的峰位移来看，不均匀展宽估计为 Soret 谱带总宽度的约 15%，A1 中约占总宽度的 60%。我们之前测量了结合的 CO 和血红素法线之间的倾斜角 α (Ormos, P., D. Braunstein, H. Frauenfelder, M. K. Hong, S.-L. Lin, T. B. Sauke, 和 R. D. Young. 1988. Proc. Natl. Acad. Sci. USA. 85:8492–8496) 并观察了 CO 拉伸 A 内倾斜角的波数依赖性 乐队。因此，A 带的光谱和焓分布与结构的异质性相关。
The rebinding kinetics of CO to myoglobin after flash photolysis is nonexponential in time below approximately 180 K; the kinetics is governed by a distribution of enthalpic barriers. This distribution results from inhomogeneities in the protein conformation, referred to as conformational substates. Hole-burning experiments on the Soret and IR CO-stretch bands test the assumption that an inhomogeneous distribution of conformational substates results in inhomogeneously broadened spectra. CO was slowly photolyzed at different wavelengths in the Soret band at 10 K. Both the Soret band and the CO-stretch band A1, centered at 1,945 cm-1, shift during photolysis, demonstrating that different wavelengths excite different parts of the distributed population. We have also done kinetic hole-burning experiments by measuring peak shifts in the Soret and A1 bands as the CO molecules rebind. The shifts indicate that the spectral and enthalpic distributions are correlated. In the A1 band, the spectral and enthalpic distributions are highly correlated while in the Soret the correlation is weak. From the peak shifts in the spectral and kinetic hole-burning experiments the inhomogeneous broadening is estimated to be approximately 15% of the total width in the Soret band and approximately 60% in A1. We have previously measured the tilt angle alpha between the bound CO and the heme normal (Ormos, P., D. Braunstein, H. Frauenfelder, M. K. Hong, S.-L. Lin, T. B. Sauke, and R. D. Young. 1988. Proc. Natl. Acad. Sci. USA. 85:8492–8496) and observed a wave number dependence of the tilt angles within the CO-stretch A bands. Thus the spectral and enthalpic distributions of the A bands are coupled to a heterogeneity of the structure.