Tracing the 267 nm-Induced Radical Formation in Dimethyl Disulfide Using Time-Resolved X-ray Absorption Spectroscopy
Tracing the 267 nm-Induced Radical Formation in Dimethyl Disulfide Using Time-Resolved X-ray Absorption Spectroscopy
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DOI：
10.1021/acs.jpclett.9b00159
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发表时间：
2019-03-21
影响因子：
5.7
通讯作者：
Gessner, Oliver
中科院分区：
文献类型：
--
作者：
Schnorr, Kirsten;Bhattacherjee, Aditi;Gessner, Oliver
二硫键对蛋白质的结构、功能和稳定性起着至关重要的作用，了解紫外线(UV)诱导的S-S键断裂对于阐明蛋白质光化学的基本机制具有重要意义。本文用超快瞬时X射线吸收光谱研究了具有S-S键的原型体系--二甲基二硫醚的近紫外光分解机理。利用飞秒高次谐波光源的宽带软X射线能谱，在硫的L-1、L-2、L-3边和碳K边同时监测了解离过程中和解离后的电子结构演变，时间分辨率为100fS(半高宽)。利用ADC和RASPT2电子结构计算对解离产物进行了鉴定。在267 nm辐射激发下，在120+/-30fs内迅速解离为两个CH3S自由基是主要的弛豫途径。此外，CH3自由基的出现表明了CH3S2+CH3不对称解离的30+/-10%的贡献，然而，这至少部分是多光子激发的结果。
Disulfide bonds are pivotal for the structure, function, and stability of proteins, and understanding ultraviolet (UV)-induced S-S bond cleavage is highly relevant for elucidating the fundamental mechanisms underlying protein photochemistry. Here, the near-UV photodecomposition mechanisms in gas-phase dimethyl disulfide, a prototype system with a S-S bond, are probed by ultrafast transient X-ray absorption spectroscopy. The evolving electronic structure during and after the dissociation is simultaneously monitored at the sulfur L-1,L-2,L-3-edges and the carbon K-edge with 100 fs (FWHM) temporal resolution using the broadband soft X-ray spectrum from a femtosecond high-order harmonics light source. Dissociation products are identified with the help of ADC and RASPT2 electronic-structure calculations. Rapid dissociation into two CH3S radicals within 120 +/- 30 fs is identified as the major relaxation pathway after excitation with 267 nm radiation. Additionally, a 30 +/- 10% contribution from asymmetric CH3S2 + CH3 dissociation is indicated by the appearance of CH3 radicals, which is, however, at least partly the result of multiphoton excitation.