Excited-state intermolecular proton transfer of firefly luciferin IV. Temperature and pH dependence.
Excited-state intermolecular proton transfer of firefly luciferin IV. Temperature and pH dependence.
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DOI：
10.1021/jp110889v
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发表时间：
2011-03
期刊：
影响因子：
--
通讯作者：
Y. Erez;Itay Presiado;R. Gepshtein;D. Huppert
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文献类型：
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作者：
Y. Erez;Itay Presiado;R. Gepshtein;D. Huppert
采用时间分辨发射光谱和稳态紫外-可见光谱技术研究了萤火虫荧光素酶的天然底物d-glycoprotein在酸性水溶液和冰溶液中的光质子分解过程。在20 mM HCl水溶液或更高浓度下的D-甜菊素的发射光谱具有相对于pH中性水溶液中去质子化NRO（-*）形式的位于530 nm处的最强发射带红移的位于590 nm处的额外发射带。我们将此发射带归因于指定为（+）HNRO（-）的两性离子形式。时间分辨的发射信号表明，在530 nm处的NRO（-*）发射带和在590处的两性离子发射带被质子在酸性溶液和冰中的复合过程强烈猝灭。在冰中，淬灭速率比在液态中快10倍。我们归因于快速淬火速率的高值的质子在冰中的扩散常数。
Time-resolved emission as well as steady-state UV-vis techniques were employed to study the photoprotolytic processes that d-luciferin, the natural substrate of the firefly luciferase, undergoes in both acidic aqueous solutions and ice. The emission spectrum of D-luciferin in a 20 mM HCl aqueous solution or higher has an additional emission band at 590 nm red-shifted with respect to the strongest emission band positioned at 530 nm of the deprotonated NRO(-*) form in a pH-neutral aqueous solution. We attribute this emission band to the zwitterion form designated as (+)HNRO(-). The time-resolved emission signals show that the NRO(-*) emission band at 530 nm and the zwitterion emission band at 590 are strongly quenched by a recombination process with a proton in an acidic solution and in ice. In ice, the quenching rate is 10 times faster than in the liquid state. We attribute the fast quenching rate to the high value of the proton diffusion constant in ice.