Naslov
Keto or Enol—That is the Question: Steady-state and Time-resolved Spectroscopy of Firefly Oxyluciferin and its Derivatives

Autori
Naumov, Panče ; Solntsev ; Kyril M. ; Laptenok, Sergey ; Rebarz, Mateusz ; Kukovec ; Boris-Marko ; Maltsev, Oleg V. ; Ruckebusch, Cyril ; Sliwa, Michel ; Hintermann, Lukas

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
2nd DYCE-ASIA Workshop/ISSP International Workshop on Life Science and Photonics, University of Tokyo (Kashiwa Campus)

Mjesto i datum
Tokyo, Japan, 17.12.2013. - 18.12.2013

Vrsta sudjelovanja
Pozvano predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
oxyluciferin; steady-state spectroscopy; time-resolved spectroscopy

Sažetak
Despite being of critical relevance for the bioanalytical performance, two key aspects of the firefly bioluminescence (BL) have long remained a subject of speculation and dispute. First, the exact chemical identity of oxyluciferin (OxyLH2) complexed with the luciferase (Luc) at various stages of the BL reaction sequence and at various conditions has not been determined yet. A second thoroughly debated issue is the molecular origin of natural or artificially (point-mutation) induced tuning of the emission energy. In this work, the most recent results from our steady-state and time-resolved spectroscopy of OxyLH2 and its derivatives will be described. These results provide direct insight into the structure and fate of different forms of the emitter in solvated form and when complexed with Luc. By studying the photochemical behavior of several synthetic derivatives, we have assessed the effects of its functional groups and support the assignments by two non-natural fluorophores. The natural emitter OxyLH2 has been studied intensively, and it behaves as a typical photoacid with an estimated pKa* of 0.5. Despite the common belief that the hydroxyl of the thiazoline- substituted phenolic group serves as a source of photogenerated protons, we were very surprised to observe excited-state proton transfer (ESPT) from HOxy, which has only one enolic hydroxyl group. Moreover, the photoacidity of HOxy was stronger than of the parent OxyLH2. Usually the HO- photoacids are based on the phenolic compounds, and the examples of non-traditional photoacids are extremely rare. We are tempted to conclude that the ESPT reactivity associated with the phenol photodissociation was misinterpreted. Based on these observations, we interpreted the photoiduced behavior of OxyLH2 in water and in the complex with Luc as a complex ESPT cascade. Depending on pH, the emitting species included keto- and enol tautomers in various protonation steps. Our spectral assignments could be directly utilized in the analysis of the multiband Luc chemiluminescence spectra.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA