title: Excited-state intermolecular proton transfer of the firefly's chromophore D-luciferin.
abstract: Steady-state absorption and emission as well as time-resolved emission spectroscopies were employed to study the photophysics and photochemistry of D-luciferin, the firefly active bioluminescent compound. In aqueous solution the electronically excited-state protonated D-luciferin compound undergoes an efficient process of proton transfer to the solvent, with a rate constant k(PT) = 3.0 x 10(10) s(-1). We found a kinetic isotope effect of about 2.5 for this process. The deprotonated form of D-luciferin in the excited state recombines irreversibly with the geminate proton. Hence, the fluorescence decay of the deprotonated form is nonexponential, and the fluorescence quantum yield is low.
authors.affiliation: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Erez
authors.forename: Dan
authors.initials: D
authors.lastname: Huppert
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D052160:Benzothiazoles / Q000737:chemistry*; D055162:Biocatalysis; D002413:Cations, Divalent; D048888:Fireflies / Q000737:chemistry*; D049454:Firefly Luciferin / Q000737:chemistry*; D007700:Kinetics; D049408:Luminescent Agents / Q000737:chemistry*; D008163:Luminescent Measurements; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism; D010084:Oxidation-Reduction; D011522:Protons; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D002413:Cations, Divalent; C532924:D-luciferin; D049408:Luminescent Agents; D011522:Protons; D012997:Solvents; D014867:Water; D049454:Firefly Luciferin; D000255:Adenosine Triphosphate; D008274:Magnesium