Photochemistry in dried polymer films incorporating the deionized blue membrane form of bacteriorhodopsin.
Photochemistry in dried polymer films incorporating the deionized blue membrane form of bacteriorhodopsin.
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含有去离子蓝膜形式细菌视紫红质的干燥聚合物薄膜中的光化学。
DOI：
10.1016/s0006-3495(98)77605-2
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发表时间：
1998
影响因子：
3.4
通讯作者：
Birge,RR
中科院分区：
文献类型：
--
作者：
Tallent,JR;Stuart,JA;Song,QW;Schmidt,EJ;Martin,CH;Birge,RR
研究了聚乙烯醇膜中干燥去离子蓝膜（dIbR 600;λmax <$600nm，λ max 54，760 cm-1 M-1，f <$1.1）的制备及其光化学性质。在强647-nm激光照射条件下，这些薄膜中发生了从dIbR 600到粉红色膜（dIbR 485;λmax≈ 485 nm）的可逆光转换。粉红色的膜类似物dIbR 485的摩尔消光系数为39，000 cm − 1 M −1（f = 1.2）。粉红色→蓝色和蓝色→粉红色的量子效率之比为33±5。我们观察到一个额外的蓝移物种（dIbR 455，λmax <$455 nm），具有非常低的振子强度（f <$0.6，λ = 26，000 cm − 1 M −1）。这种物质是dIbR 485快速热衰变的产物。分子模拟表明，由ASP 85质子化引入的电荷/电荷和电荷/偶极相互作用导致激发态全反式→9-顺式势垒降低到1.6kcal mol− 1，而相应的全反式→13-顺式势垒增加到1.4kcal mol−1。正如实验所观察到的那样，9-顺式和13-顺式光产物的光化学形成现在是竞争性的。我们认为dIbR 455可能是一个9-cis，10-s-畸变的分子，它将发色团部分地分成两个局部共轭片段，并伴随着蓝移和λ max吸收带振子强度的降低。
The preparation and photochemical properties of dried deionized blue membrane (dIbR600;λmax≈600nm, ϵ≈54, 760cm−1M−1, f≈1.1) in polyvinyl alcohol films are studied. Reversible photoconversion from dIbR600to the pink membrane (dIbR485;λmax≈485nm) is shown to occur in these films under conditions of strong 647-nm laser irradiation. The pink membrane analog, dIbR485, has a molar extinction coefficient of ∼39,000cm−1M−1(f≈1.2). The ratio of pink→blue and blue→pink quantum efficiencies is 33±5. We observe an additional blue-shifted species (dIbR455,λmax≈455nm) with a very low oscillator strength (f≈0.6, ϵ≈26,000cm−1M−1). This species is the product of fast thermal decay of dIbR485. Molecular modeling indicates that charge/charge and charge/dipole interactions introduced by the protonation of ASP85are responsible for lowering the excited-state all-trans→9-cisbarrier to ∼6kcal mol−1while increasing the corresponding all-trans→13-cisbarrier to ∼4kcal mol−1. Photochemical formation of both 9-cisand 13-cisphotoproducts are now competitive, as is observed experimentally. We suggest that dIbR455may be a 9-cis, 10-s-distorted species that partially divides the chromophore into two localized conjugated segments with a concomitant blue shift and decreased oscillator strength of theλmaxabsorption band.