Absorption of Schiff-base retinal chromophores in vacuo
Absorption of Schiff-base retinal chromophores in vacuo
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DOI：
10.1021/ja051638j
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发表时间：
2005-09-07
影响因子：
15
通讯作者：
Petersen, MÅ
中科院分区：
文献类型：
--
作者：
Andersen, LH;Nielsen, IB;Petersen, MÅ
在真空中测量了质子化席夫碱形式（即生物学相关形式）的全反式视网膜发色团的吸收光谱，在610 nm处发现最大值。迄今为止，将视黄醇蛋白的吸收与质子化的视黄醇在甲醇中的吸收进行比较，其中最大吸收在440 nm处。相比之下，新的气相吸收数据构成了一个定义明确的参考，在没有电荷和偶极子的环境中的视紫红质光谱调谐。它们取代了与溶剂中吸收特性的误导性比较，并为重新考虑视网膜蛋白大家族中颜色调节的分子机制奠定了基础。事实上，我们的测量直接表明，视紫红质中的蛋白质环境是蓝色的，而不是红移吸收。本文还研究了中性席夫碱对视网膜模型发色团的吸收。这些数据解释了当甲基视紫红质I被去质子化时发生的显著蓝移以及细菌视紫红质在酸化时的紫色到蓝色转变。
The absorption spectrum of the all-trans retinal chromophore in the protonated Schiff-base form, that is, the biologically relevant form, has been measured in vacuo, and a maximum is found at 610 nm. The absorption of retinal proteins has hitherto been compared to that of protonated retinal in methanol, where the absorption maximum is at 440 nm. In contrast, the new gas-phase absorption data constitute a well-defined reference for spectral tuning in rhodopsins in an environment devoid of charges and dipoles. They replace the misleading comparison with absorption properties in solvents and lay the basis for reconsidering the molecular mechanisms of color tuning in the large family of retinal proteins. Indeed, our measurement directly shows that protein environments in rhodopsins are blue- rather than red shifting the absorption. The absorption of a retinal model chromophore with a neutral Schiff base is also studied. The data explain the significant blue shift that occurs when metharhodopsin I becomes deprotonated as well as the purple-to-blue transition of bacteriorhodopsin upon acidification.