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 talk, the most recent results from our steady-state[1�3] and time-resolved[4] spectroscopic and structural studies 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 several non-natural fluorophores. 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.[1] J. Am. Chem. Soc. 2009; 131  : 11590�11605. [2] J. Am. Chem. Soc. 2010; 132  : 11566�11579. [3] Chem. Sci. 2013; 4  : 3803�3809. [4] J. Am. Chem. Soc. 2012; 134 , 16452�16455.

Firefly bioluminescence: A spectroscopic perspective

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.