TRANSIENT RAMAN-STUDY OF CO-HEMOPROTEIN PHOTOLYSIS - ORIGIN OF THE QUANTUM YIELD
TRANSIENT RAMAN-STUDY OF CO-HEMOPROTEIN PHOTOLYSIS - ORIGIN OF THE QUANTUM YIELD
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DOI：
10.1038/284570a0
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发表时间：
1980-01-01
期刊：
影响因子：
64.8
通讯作者：
LYONS, KB
中科院分区：
文献类型：
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作者：
FRIEDMAN, JM;LYONS, KB
一氧化碳和血蛋白 (Fe2+) 形成配体-蛋白质复合物，可通过可见光以高量子效率光解离1,2。通过用脉冲激光辐射光解CO-蛋白质复合物，可以产生瞬态物质，其特性反映光解和重组过程的性质以及非平衡蛋白质动力学。使用单脉冲光解和检查样品，我们之前报道了碳氧血红蛋白 (HbCO) 光解 10 ns 内发生的瞬态血红蛋白 (Hb) 的共振拉曼光谱。通过使用涵盖皮秒 4-6、纳秒 7-10 和更长时间尺度 11-15 的瞬态吸收光谱，对光解 HbCO 产生的瞬态物质进行了深入研究。与各种物种相关的吸收带的重叠可能会妨碍从吸收光谱中提取定量信息。尽管如此，已经报道了进展，特别是在本文描述的实验顺利进行之后报告的纳秒瞬态吸收研究9,10的结果。这些结果，包括对早期数据的重新解释8，得出了这样的建议9,10：HbCO 的光解实际上导致脱氧 Hb 物质的量子产率接近一致，然后在 100 ns 内发生大量重组。我们在这里提供来自 1,350–1,380-cm−1 区域拉曼光谱的明确证据，其中 HbCO 和脱氧 Hb 物种表现出良好分离的峰，表明这种解释确实是正确的。我们还准确测量了 HbCO 总体作为完全光解后延迟时间的函数，从而测量了重组过程的动力学。我们的研究结果直接涉及诸如成对重组以及 HbCO 和碳氧肌红蛋白 (MbCO) 光解量子产率差异的起源等问题。当在可见光中强烈泵浦时，这两个系统表现出截然不同的量子产率：MbCO 经历 97% 的光解，而 HbCO 仅经历 45-47%（参考文献 15）。
Carbon monoxide and haemoproteins (Fe2+) form ligand–protein complexes that are photodissociated with high quantum efficiency by visible light1,2. By photolysing the CO–protein complex with pulsed laser radiation it is possible to generate transient species with properties which reflect both the nature of the photolytic and recombination processes as well as non-equilibrium protein dynamics. Using a single pulse both to photolyse and examine the sample, we previously reported3the resonance Raman spectrum of a transient species of haemoglobin (Hb) occurring within 10 ns of the photodissociation of carboxyhaemoglobin (HbCO). Transient species generated by photodissociating HbCO have been intensively studied by using transient absorption spectroscopy covering picosecond4–6, nanosecond7–10and longer time scales11–15. The overlap of the absorption bands related to various species can hamper the extraction of quantitative information from absorption spectra. Nevertheless, progress has been reported, in particular, the results of nanosecond transient absorption studies9,10reported after the experiments described here were well under way. Those results, including re-interpretation of earlier data8, led to the suggestion9,10that photolysis of HbCO actually leads to a near-unity quantum yield of a deoxy-Hb species, followed by substantial recombination within 100 ns. We present here definitive evidence from Raman spectra of the 1,350–1,380-cm−1region, where the HbCO and deoxy-Hb species exhibit well separated peaks, that this interpretation is indeed correct. We have also measured accurately the HbCO population as a function of delay time after full photolysis, and thereby measured the kinetics of the recombination process. Our findings bear directly on such questions as geminate recombination and the origin of the difference in quantum yield of photodissociation for HbCO and carboxymyoglobin (MbCO). These two systems exhibit very different quantum yields when strongly pumped in the visible: MbCO undergoes 97% photolysis whereas HbCO undergoes only 45–47% (ref. 15).