Conformational Homogeneity in the Pr Isomer of Phytochrome Cph l
Conformational Homogeneity in the Pr Isomer of Phytochrome Cph l
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DOI：
10.1021/acs.jpcb.7b02180
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发表时间：
2017-03-30
影响因子：
3.3
通讯作者：
Turner, Daniel B.
中科院分区：
文献类型：
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作者：
Bizimana, Laurie A.;Epstein, Jordan;Turner, Daniel B.
光敏色素Cphl中P-r到P-fr光异构化的大量时间分辨研究揭示了多相激发态衰减动力学。目前还不清楚这些动力学是否产生于多个基态构象亚群或从一个单一的基态构象，经历了激发态光异构化过程中的分支激发态或放松通过多个顺序的中间体。许多研究试图通过将测量的动力学与提出的动力学模型拟合来解决这一争论，得出了不同的结论。在这里，我们探测光谱特征的基态异质性Pr。二维电子光谱显示可以忽略不计的不均匀线加宽，和振动相干光谱提取的瞬态吸收测量不包含节点和相移的荧光最大值。这些光谱结果支持了均相模型，其中P-r到Lumi-R的初级光化学转化在激发态P-态势能面上发生。
Numerous time-resolved studies of the P-r to P-fr photoisomerization in phytochrome Cphl have revealed multiphasic excited-state decay kinetics. It remains unclear whether these kinetics arise from multiple ground-state conformational subpopulations or from a single ground-state conformation that undergoes an excited-state photoisomerization process either branching on the excited state or relaxing through multiple sequential intermediates. Many studies have attempted to resolve this debate by fitting the measured dynamics to proposed kinetic models, arriving at different conclusions. Here we probe spectral signatures of ground-state heterogeneity of Pr. Two-dimensional electronic spectra display negligible inhomogeneous line broadening, and vibrational coherence spectra extracted from transient absorption measurements do not contain nodes and phase shifts at the fluorescence maximum. These spectroscopic results support the homogeneous model, in which the primary photochemical transformation of P-r to Lumi-R occurs adiabatically on the excited P-state potential energy surface.