Santus R, Patterson L K, Bazin M, Mazière J C, Morlière P
Laboratoire de Photobiologie (INSERM U 312) Muséum National d'Histoire Naturelle, Paris, France.
Free Radic Res. 1998 Nov;29(5):409-19. doi: 10.1080/10715769800300451.
The reaction of the superoxide radical anion (O2-), with the semi-oxidized tryptophan neutral radical (Trp) generated from tryptophan (Trp) by pulse radiolysis has been observed in a variety of functionalized Trp derivatives including peptides. It is found that the reaction proceeds 4-5 times faster in positively charged peptides, such as Lys-Trp-Lys, Lys-Gly-Trp-Lys and Lys-Gly-Trp-Lys-O-tert-butyl, than in solutions of the negatively charged N-acetyl tryptophan (NAT). However, the reactivity of O2-* with the Trp* radical is totally inhibited upon binding of these peptides to micelles of negatively charged SDS and is reduced upon binding to native DNA. By contrast, no change in reactivity is observed in a medium containing CTAB, where the peptides cannot bind to the positively charged micelles. On the other hand, the reactivity of the Trp* radical formed from NAT with O2-* is reduced to half that of the free Trp* in buffer but is markedly increased in CTAB micelles. The models studied here incorporate elements of the complex environment in which Trp* and O2-* may be concomitantly formed in biological system and demonstrate the magnitude of the influence such elements may have on the kinetics of reactions involving these two species.
在包括肽在内的多种功能化色氨酸衍生物中，通过脉冲辐解观察到超氧自由基阴离子（O2-）与色氨酸（Trp）产生的半氧化色氨酸中性自由基（Trp）之间的反应。研究发现，在带正电荷的肽中，如赖氨酸-色氨酸-赖氨酸、赖氨酸-甘氨酸-色氨酸-赖氨酸和赖氨酸-甘氨酸-色氨酸-赖氨酸-O-叔丁酯，该反应的进行速度比带负电荷的N-乙酰色氨酸（NAT）溶液快4-5倍。然而，当这些肽与带负电荷的十二烷基硫酸钠（SDS）胶束结合时，O2-与Trp自由基的反应性完全被抑制，而与天然DNA结合时反应性降低。相比之下，在含有十六烷基三甲基溴化铵（CTAB）的介质中未观察到反应性变化，因为肽不能与带正电荷的胶束结合。另一方面，由NAT形成的Trp自由基与O2-的反应性在缓冲液中降至游离Trp的一半，但在CTAB胶束中显著增加。这里研究的模型包含了生物系统中可能同时形成Trp和O2-*的复杂环境的元素，并证明了这些元素对涉及这两种物质的反应动力学可能产生的影响程度。
