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首页> 外文期刊>Biochemistry >Primary Photodynamics of the Green/Red-Absorbing Photoswitching Regulator of the Chromatic Adaptation E Domain from Fremyella diplosiphon
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Primary Photodynamics of the Green/Red-Absorbing Photoswitching Regulator of the Chromatic Adaptation E Domain from Fremyella diplosiphon

机译：Fremyella diplosiphon的色适应E域的绿色/红色吸收光开关调节器的主要光动力学。

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摘要

Phytochromes are red/far-red photosensory proteins that utilize the photoisomerization of a linear tetrapyrrole (bilin) chromophore to detect the red to far-red light ratio. Cyanobacteriochromes (CBCRs) are distantly related cyanobacterial photosensors with homologous bilinbinding GAF domains, but they exhibit greater spectral diversity. Different CBCR subfamilies have been described, with spectral sensitivity varying across the near-ultraviolet and throughout the visible spectrum, but all known CBCRs utilize photoisomerization of the bilin 15,16-double bond as the primary photochemical event. The first CBCR discovered was RcaE, responsible for tuning light harvesting to the incident color environment (complementary chromatic adaptation) in Fremyella diplosiphon. The green/red RcaE photocycle has recently been described in detail. We now extend this analysis by examining femtosecond photodynamics using ultrafast transient absorption techniques with broadband detection and multicomponent global analysis. Excited-state dynamics in both directions are significantly slower than those recently published for the red/green CBCR NpR6012g4. In the forward reaction, the primary Lumi-G photoproduct arises from the longer-lived excited-state populations, leading to a low photoproduct quantum yield. Using dual-excitation wavelength interleaved pump? probe spectroscopy, we observe multiphasic excited-state dynamics in the forward reaction (~(15Z)P_g → ~(15E)P_r), which we interpret as arising from ground-state inhomogeneity with different tautomers of the PCB chromophore. The reverse reaction (~(15E)P_r → ~(15Z)P_g) is characterized via pump?probe spectroscopy and also exhibits slow excited-state decay dynamics and a low photoproduct yield. These results provide the first description of excited-state dynamics for a green/red CBCR.
机译：植物色素是红色/远红色的光敏蛋白质，利用线性四吡咯（胆素）生色团的光异构化来检测红光与远红光的比率。蓝细菌色素（CBCR）是具有同源bilinbinding GAF域的遥远相关的蓝细菌光电传感器，但它们表现出更大的光谱多样性。已经描述了不同的CBCR亚家族，其光谱灵敏度在近紫外光和整个可见光谱范围内变化，但是所有已知的CBCRs都将Bilin 15,16-双键的光异构化作为主要的光化学事件。发现的第一个CBCR是RcaE，它负责将光敏双歧杆菌的光收集调整到入射颜色环境（互补色适应）。最近已经详细描述了绿色/红色RcaE光循环。现在，我们通过使用具有宽带检测和多组分全局分析的超快速瞬态吸收技术来检查飞秒光动力学，从而扩展了这一分析范围。两个方向的激发态动力学比最近发布的红色/绿色CBCR NpR6012g4慢。在正向反应中，主要的Lumi-G光产物来自寿命更长的激发态族，从而导致低的光产物量子产率。使用双激发波长交错泵？探针光谱法，我们观察到正向反应（〜（15Z）P_g→〜（15E）P_r）中的多相激发态动力学，我们将其解释为是由PCB生色团的不同互变异构体引起的基态不均匀性引起的。反向反应（〜（15E）P_r→〜（15Z）P_g）通过泵浦探针光谱法进行表征，并且还表现出缓慢的激发态衰减动力学和低的光产物产率。这些结果为绿色/红色CBCR的激发态动力学提供了第一个描述。

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