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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Photooxidation of Glycylglycine. Two-Channel Reaction Mechanism as Studied by Time-Resolved FT EPR
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Photooxidation of Glycylglycine. Two-Channel Reaction Mechanism as Studied by Time-Resolved FT EPR

机译：甘氨酰甘氨酸的光氧化。时间分辨FT EPR研究的两通道反应机理

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摘要

The Fourier transform electron paramagnetic resonance (FT EPR) spectroscopy has been employed as a detection technique in the investigation of the photooxidation of glycylglycine dipeptide induced by triplet-sensitized electron transfer to 9,10-anthraquinone-2,6-disulfonate in aqueous solutions at pH 6-10. Spin-polarized (CIDEP) radical species ~+NH_3/NH_2-CH_2-CONH-~·CH_2 and ~·NH-CH_2-CONH-CH_2-COO~- were identified as transient products formed on the nanosecond time scale. The radicals have been found to originate from two different reaction channels depending on the pH. The first channel, leading to the decarboxylated radical product, occurs in the whole pH range and is ascribed to the oxidative attack of the triplet on the peptide and/or carboxylate functional groups. At pH > 8 where the peptide terminal amino group exists in deprotonated form, the second channel, electron transfer from the amino group nitrogen nonbonding electron pair followed by deprotonation, becomes possible. This reaction leads to the formation of the observed aminyl radical.
机译：傅里叶变换电子顺磁共振（FT EPR）光谱已被用作检测技术，用于研究三重态敏化电子转移至水溶液中的三重敏化电子诱导的甘氨酰甘氨酸二肽向9,10-蒽醌-2,6-二磺酸盐的光氧化。 pH 6-10。自旋极化（CIDEP）自由基种类〜+ NH_3 / NH_2-CH_2-CONH-〜·CH_2和〜·NH-CH_2-CONH-CH_2-COO〜-被确定为在纳秒级时标上形成的瞬态产物。已经发现自由基取决于pH而源自两个不同的反应通道。导致脱羧自由基产物的第一通道在整个pH范围内发生，并归因于三重态对肽和/或羧酸酯官能团的氧化攻击。在肽端氨基以去质子形式存在的pH> 8的情况下，第二条通道可以从氨基氮非键电子对进行电子转移，然后去质子化。该反应导致形成观察到的氨基自由基。

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