Vengris Mikas, van der Horst Michael A, Zgrablic Goran, van Stokkum Ivo H M, Haacke Stefan, Chergui Majed, Hellingwerf Klaas J, van Grondelle Rienk, Larsen Delmar S
Faculty of Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.
Biophys J. 2004 Sep;87(3):1848-57. doi: 10.1529/biophysj.104.043224.
Wavelength- and time-resolved fluorescence experiments have been performed on the photoactive yellow protein, the E46Q mutant, the hybrids of these proteins containing a nonisomerizing "locked" chromophore, and the native and locked chromophores in aqueous solution. The ultrafast dynamics of these six systems is compared and spectral signatures of isomerization and solvation are discussed. We find that the ultrafast red-shifting of fluorescence is associated mostly with solvation dynamics, whereas isomerization manifests itself as quenching of fluorescence. The observed multiexponential quenching of the protein samples differs from the single-exponential lifetimes of the chromophores in solution. The locked chromophore in the protein environment decays faster than in solution. This is due to additional channels of excited-state energy dissipation via the covalent and hydrogen bonds with the protein environment. The observed large dispersion of quenching timescales observed in the protein samples that contain the native pigment favors both an inhomogeneous model and an excited-state barrier for isomerization.
已对光活性黄色蛋白、E46Q突变体、包含非异构化“锁定”发色团的这些蛋白的杂交体以及水溶液中的天然和锁定发色团进行了波长和时间分辨荧光实验。比较了这六个系统的超快动力学，并讨论了异构化和溶剂化的光谱特征。我们发现荧光的超快红移主要与溶剂化动力学相关，而异构化表现为荧光猝灭。观察到的蛋白质样品的多指数猝灭不同于溶液中发色团的单指数寿命。蛋白质环境中的锁定发色团比在溶液中衰减得更快。这是由于通过与蛋白质环境的共价键和氢键产生的激发态能量耗散的额外通道。在含有天然色素的蛋白质样品中观察到的猝灭时间尺度的大分散有利于非均匀模型和异构化的激发态势垒。
