Excited-State Intermolecular Proton Transfer of Firefly Luciferin III. Proton Transfer to a Mild Base
Steady-state and time-resolved techniques were employed to study the excited-state proton transfer (ESPT) from d-luciferin, the natural substrate of the firefly luciferase, to the mild acetate base in aqueous solutions. We found that in 1 M aqueous solutions of acetate or higher, a proton transfer (...
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Veröffentlicht in: | The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2010-12, Vol.114 (51), p.13337-13346 |
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Sprache: | eng |
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Zusammenfassung: | Steady-state and time-resolved techniques were employed to study the excited-state proton transfer (ESPT) from d-luciferin, the natural substrate of the firefly luciferase, to the mild acetate base in aqueous solutions. We found that in 1 M aqueous solutions of acetate or higher, a proton transfer (PT) process to the acetate takes place within 30 ps in both H2O and D2O solutions. The time-resolved emission signal is composed of three components. We found that the short-time component decay time is 300 and 600 fs in H2O and D2O, respectively. This component is attributed either to a PT process via the shortest water bridged complex available, ROH··H2O··Ac−, or to PT taking place within a contact ion pair. The second time component of 2000 and 3000 fs for H2O and D2O, respectively, is attributed to ROH* acetate complex, whose proton wire is longer by one water molecule. The decay rate of the third, long-time component is proportional to the acetate concentration. We attribute it to the diffusion-assisted reaction as well as to PT process to the solvent. |
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ISSN: | 1089-5639 1520-5215 |
DOI: | 10.1021/jp107360d |