Vengris Mikas, Larsen Delmar S, van der Horst Michael A, Larsen Olaf F A, Hellingwerf Klaas J, van Grondelle Rienk
Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
J Phys Chem B. 2005 Mar 10;109(9):4197-208. doi: 10.1021/jp045763d.
Pump-probe and pump-dump probe experiments have been performed on several isolated model chromophores of the photoactive yellow protein (PYP). The observed transient absorption spectra are discussed in terms of the spectral signatures ascribed to solvation, excited-state twisting, and vibrational relaxation. It is observed that the protonation state has a profound effect on the excited-state lifetime of p-coumaric acid. Pigments with ester groups on the coumaryl tail end and charged phenolic moieties show dynamics that are significantly different from those of other pigments. Here, an unrelaxed ground-state intermediate could be observed in pump-probe signals. A similar intermediate could be identified in the sinapinic acid and in isomerization-locked chromophores by means of pump-dump probe spectroscopy; however, in these compounds it is less pronounced and could be due to ground-state solvation and/or vibrational relaxation. Because of strong protonation-state dependencies and the effect of electron donor groups, it is argued that charge redistribution upon excitation determines the twisting reaction pathway, possibly through interaction with the environment. It is suggested that the same pathway may be responsible for the initiation of the photocycle in native PYP.
对光活性黄色蛋白（PYP）的几种分离的模型发色团进行了泵浦 - 探测和泵浦 - 倾卸探测实验。根据归因于溶剂化、激发态扭曲和振动弛豫的光谱特征，对观察到的瞬态吸收光谱进行了讨论。观察到质子化状态对对香豆酸的激发态寿命有深远影响。在香豆酰尾端带有酯基和带电酚基的色素显示出与其他色素显著不同的动力学。在这里，可以在泵浦 - 探测信号中观察到未弛豫的基态中间体。通过泵浦 - 倾卸探测光谱法，可以在芥子酸和异构化锁定的发色团中鉴定出类似的中间体；然而，在这些化合物中，它不太明显，可能是由于基态溶剂化和/或振动弛豫。由于强烈的质子化状态依赖性和电子供体基团的影响，有人认为激发时的电荷重新分布决定了扭曲反应途径，可能是通过与环境的相互作用。有人提出，相同的途径可能负责天然PYP中光循环的启动。
