Hiyama Miyabi, Akiyama Hidefumi, Koga Nobuaki
Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, Japan.
Graduate School of Information Science, Nagoya University, Nagoya, Japan.
Luminescence. 2017 Sep;32(6):1100-1108. doi: 10.1002/bio.3308. Epub 2017 Apr 20.
To elucidate the emission process of firefly d-luciferin oxidation across the pH range of 7-9, we identified the emission process by comparison of the potential and free-energy profiles for the formation of the firefly substrate and emitter, including intermediate molecules such as d-luciferyl adenylate, 4-membered dioxetanone, and their deprotonated chemical species. From these relative free energies, it is observed that the oxidation pathway changes from d-luciferin → deprotonated d-luciferyl adenylate → deprotonated 4-membered dioxetanone → oxyluciferin to deprotonated d-luciferin → deprotonated d-luciferyl adenylate → deprotonated 4-membered dioxetanone → oxyluciferin with increasing pH value. This indicates that deprotonation on 6'OH occurs during the formation of dioxetanone at pH 7-8, whereas luciferin in the reactant has a 6'OH-deprotonated form at pH 9.
为了阐明萤火虫d - 荧光素在pH值7 - 9范围内氧化的发光过程，我们通过比较萤火虫底物和发光体形成过程中的电位和自由能曲线来确定发光过程，其中包括中间分子，如d - 荧光素腺苷酸、四元二氧杂环丁酮及其去质子化的化学物种。从这些相对自由能可以观察到，随着pH值的增加，氧化途径从d - 荧光素→去质子化的d - 荧光素腺苷酸→去质子化的四元二氧杂环丁酮→氧化荧光素变为去质子化的d - 荧光素→去质子化的d - 荧光素腺苷酸→去质子化的四元二氧杂环丁酮→氧化荧光素。这表明在pH值7 - 8时，二氧杂环丁酮形成过程中6'OH发生去质子化，而在pH值9时，反应物中的荧光素具有6'OH去质子化形式。
