Pinto da Silva Luís, Esteves da Silva Joaquim C G
Centro de Investigação em Química, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, R. Campo Alegre 687, 4169-007 Porto (Portugal).
Chemphyschem. 2015 Feb 2;16(2):455-64. doi: 10.1002/cphc.201402533. Epub 2014 Nov 17.
A theoretical analysis of the enol-based photoacidity of oxyluciferin in water is presented. The basis for this phenomenon is found to be the hydrogen-bonding network that involves the conjugated photobase of oxyluciferin. The hydrogen-bonding network involving the enolate thiazole moiety is stronger than that of the benzothiazole phenolate moiety. Therefore, enolate oxyluciferin should be stabilized versus the phenolate anion. This difference in strength is attributed to the fact that the thiazole moiety has more potential hydrogen-bond acceptors near the proton donor atom than the benzothiazole moiety. Moreover, the phenol-based excited-state proton transfer leads to a decrease in the hydrogen-bond acceptor potential of the thiazole atoms. The ground-state enol-based acidity of oxyluciferin is also studied. This phenomenon can be explained by stabilization of the enolate anion through strengthening of a bond between water and the nitrogen atom of the thiazole ring, in an enol-based proton-transfer-dependent way.
本文对水中氧化荧光素基于烯醇的光酸度进行了理论分析。发现这种现象的基础是涉及氧化荧光素共轭光碱的氢键网络。涉及烯醇式噻唑部分的氢键网络比苯并噻唑酚盐部分的更强。因此，相对于酚盐阴离子，烯醇式氧化荧光素应该更稳定。强度上的这种差异归因于这样一个事实，即噻唑部分在质子供体原子附近比苯并噻唑部分有更多潜在的氢键受体。此外，基于酚的激发态质子转移导致噻唑原子的氢键受体潜力降低。还研究了氧化荧光素基于烯醇的基态酸度。这种现象可以通过烯醇式质子转移依赖的方式，通过加强水与噻唑环氮原子之间的键来稳定烯醇盐阴离子来解释。
