Shih Crystal, Museth Anna Katrine, Abrahamsson Malin, Blanco-Rodriguez Ana Maria, Di Bilio Angel J, Sudhamsu Jawahar, Crane Brian R, Ronayne Kate L, Towrie Mike, Vlcek Antonín, Richards John H, Winkler Jay R, Gray Harry B
Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2008 Jun 27;320(5884):1760-2. doi: 10.1126/science.1158241.
Energy flow in biological structures often requires submillisecond charge transport over long molecular distances. Kinetics modeling suggests that charge-transfer rates can be greatly enhanced by multistep electron tunneling in which redox-active amino acid side chains act as intermediate donors or acceptors. We report transient optical and infrared spectroscopic experiments that quantify the extent to which an intervening tryptophan residue can facilitate electron transfer between distant metal redox centers in a mutant Pseudomonas aeruginosa azurin. Cu(I) oxidation by a photoexcited Re(I)-diimine at position 124 on a histidine(124)-glycine(123)-tryptophan(122)-methionine(121) beta strand occurs in a few nanoseconds, fully two orders of magnitude faster than documented for single-step electron tunneling at a 19 angstrom donor-acceptor distance.
生物结构中的能量流动通常需要在长分子距离上进行亚毫秒级的电荷传输。动力学模型表明，通过多步电子隧穿可以大大提高电荷转移速率，其中氧化还原活性氨基酸侧链充当中间供体或受体。我们报告了瞬态光学和红外光谱实验，这些实验量化了一个插入的色氨酸残基能够促进突变型铜绿假单胞菌天青蛋白中远距离金属氧化还原中心之间电子转移的程度。在组氨酸（124）-甘氨酸（123）-色氨酸（122）-甲硫氨酸（121）β链上位置124处的光激发铼（I）-二亚胺对铜（I）的氧化在几纳秒内发生，比在19埃供体-受体距离下单步电子隧穿记录的速度快整整两个数量级。
