Excited-State Proton Transfer of Firefly Dehydroluciferin

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• 作者：Itay Presiado ; Yuval Erez ; Ron Simkovitch ; Shay Shomer ; Rinat Gepshtein ; Lu铆s Pinto da Silva ; Joaquim C.G. Esteves da Silva ; Dan Huppert
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：November 8, 2012
• 年：2012
• 卷：116
• 期：44
• 页码：10770-10779
• 全文大小：589K
• 年卷期：v.116,no.44(November 8, 2012)
• ISSN：1520-5215

文摘

Steady-state and time-resolved emission techniques were used to study the protolytic processes in the excited state of dehydroluciferin, a nonbioluminescent product of the firefly enzyme luciferase. We found that the ESPT rate coefficient is only 1.1 脳 10¹⁰ s^鈥?, whereas those of class="smallcaps">d-luciferin and oxyluciferin are 3.7 脳 10¹⁰ and 2.1 脳 10¹⁰ s^鈥?, respectively. We measured the ESPT rate in water鈥搈ethanol mixtures, and we found that the rate decreases nonlinearly as the methanol content in the mixture increases. The deprotonated form of dehydroluciferin has a bimodal decay with short- and long-time decay components, as was previously found for both class="smallcaps">d-luciferin and oxyluciferin. In weakly acidic aqueous solutions, the deprotonated form鈥檚 emission is efficiently quenched. We attribute this observation to the ground-state protonation of the thiazole nitrogen, whose pK_a value is 3.