TY - JOUR
T1 - Excited-state proton transfer of firefly dehydroluciferin
AU - Presiado, Itay
AU - Erez, Yuval
AU - Simkovitch, Ron
AU - Shomer, Shay
AU - Gepshtein, Rinat
AU - Pinto Da Silva, Luís
AU - Esteves Da Silva, Joaquim C.G.
AU - Huppert, Dan
PY - 2012/11/8
Y1 - 2012/11/8
N2 - 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 × - 1010 s-1, whereas those of d-luciferin and oxyluciferin are 3.7 × - 1010 and 2.1 × - 1010 s-1, respectively. We measured the ESPT rate in water-methanol 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 d-luciferin and oxyluciferin. In weakly acidic aqueous solutions, the deprotonated forms emission is efficiently quenched. We attribute this observation to the ground-state protonation of the thiazole nitrogen, whose pKa value is ∼3.
AB - 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 × - 1010 s-1, whereas those of d-luciferin and oxyluciferin are 3.7 × - 1010 and 2.1 × - 1010 s-1, respectively. We measured the ESPT rate in water-methanol 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 d-luciferin and oxyluciferin. In weakly acidic aqueous solutions, the deprotonated forms emission is efficiently quenched. We attribute this observation to the ground-state protonation of the thiazole nitrogen, whose pKa value is ∼3.
UR - http://www.scopus.com/inward/record.url?scp=84868598507&partnerID=8YFLogxK
U2 - 10.1021/jp308818r
DO - 10.1021/jp308818r
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C2 - 23057588
AN - SCOPUS:84868598507
SN - 1089-5639
VL - 116
SP - 10770
EP - 10779
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 44
ER -