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首页> 外文期刊>Biochemistry >Femtosecond Photodynamics of the Red/Green Cyanobacteriochrome NpR6012g4 from Nostoc punctiforme. 2. Reverse Dynamics
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Femtosecond Photodynamics of the Red/Green Cyanobacteriochrome NpR6012g4 from Nostoc punctiforme. 2. Reverse Dynamics

机译：飞虱的红色/绿色蓝细菌色素NpR6012g4的飞秒光动力学。 2.逆向动力学

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Phytochromes are red/far-red photosensory proteins that utilize photoisomerization of a linear tetrapyrrole (bilin) chromophore to photoconvert reversibly between red- and far-red-absorbing forms (P_r and P_(fr), respectively). Cyanobacteriochromes (CBCRs) are related photosensory proteins with more diverse spectral sensitivity. The mechanisms that underlie this spectral diversity have not yet been fully elucidated. One of the main CBCR subfamilies photoconverts between a red-absorbing 15Z ground state, like the familiar P_r state of phytochromes, and a green-absorbing photoproduct (~(15E)P_g). We have previously used the red/green CBCR NpR6012g4 from the cyanobacterium Nostoc punctiforme to examine ultrafast photodynamics of the forward photoreaction. Here, we examine the reverse reaction. Using excitationinterleaved transient absorption spectroscopy with broadband detection and multicomponent global analysis, we observed multiphasic excited-state dynamics. Interleaved excitation allowed us to identify wavelength-dependent shifts in the ground-state bleach that equilibrated on a 200 ps time scale, indicating ground-state heterogeneity. Compared to the previously studied forward reaction, the reverse reaction has much faster excited-state decay time constants and significantly higher photoproduct yield. This work thus demonstrates striking differences between the forward and reverse reactions of NpR6012g4 and provides clear evidence of ground-state heterogeneity in the phytochrome superfamily.
机译：植物色素是红色/远红色的光敏蛋白，利用线性四吡咯（比林）生色团的光异构化在吸收红光和远红光的形式（分别为P_r和P_（fr））之间进行可逆光转化。蓝细菌色素（CBCRs）是相关的光敏蛋白，具有更高的光谱敏感性。尚未完全阐明这种频谱多样性的基础机制。主要的CBCR子家族之一在吸收光的15Z基态（如熟悉的植物色素的P_r状态）与吸收光的绿色产物（〜（15E）P_g）之间进行光转换。我们以前曾使用过来自点状蓝藻的红色/绿色CBCR NpR6012g4来检查正向光反应的超快光动力学。在这里，我们检查反向反应。使用具有宽带检测和多组分全局分析的激发交错瞬态吸收光谱，我们观察了多相激发态动力学。交错激发使我们能够确定基态漂白剂中与波长有关的位移，该位移在200 ps的时间尺度上达到平衡，表明基态异质性。与先前研究的正向反应相比，反向反应具有更快的激发态衰减时间常数和显着更高的光产物产率。因此，这项工作证明了NpR6012g4正向和反向反应之间的显着差异，并为植物色素超家族中基态异质性提供了清晰的证据。

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