There are numerous reports of coumarin ester derivatives, in particular phosphate esters, as photocleavable cages in biological systems. Despite the comprehensive analysis of the photocleavage mechanism, studies of 4-methylcoumarin caged phosphates and/or nucleotides were always performed at constant pH. In this work. we present the study of the pH effect on the photochemistry of (7-diethylaminocoumarin-4-yl)methyl phosphate (DEACM-P). Fluorescence and photocleavage quantum yields, as well as the fluorescence decay times were measured as a function of the pH. It was found that the pH produces significant changes in the overall photochemical quantum yield of DEACM-P, and the observed changes are complementary to those obtained from the fluorescence quantum yield. Deprotonation of DEACM-HPO(4)(-) to yield DEACM -PO(4)(2-), produces a decrease in the photochemical quantum yield (from 0.0045 to 0.0003) and an increase in the fluorescence quantum yield (from 0.072 to 0.092). Moreover, from the analysis of the decay times, we have also found that hydroxyl ion is not only relevant, but it is mechanistically involved in the photoreaction of DEACM-HPO(4)(-).
ISI Document Delivery No.: 690GNTimes Cited: 6
Cited Reference Count: 30
Pinheiro, Andre Vidal Jorge Parola, A. Baptista, Pedro V. Lima, J. C.
Parola, A. Jorge/F-4048-2010; Caparica, cqfb_staff/H-2611-2013; Baptista, Pedro/A-1237-2009; REQUIMTE, AL/H-9106-2013; Chaves, Pedro/K-1288-2013; Lima, Joao/F-3658-2010
Parola, A. Jorge/0000-0002-1333-9076; Baptista, Pedro/0000-0001-5255-7095; Lima, Joao/0000-0003-0528-1967
Fundacao para a Ciencia e Tecnologia [SFRH/BD/24276/2005]
The authors would like to thank Dr. Joao Pina and Professor Sergio S. Melo for the fluorescence lifetime measurements and Dr. Laura Raurell for the help in DEACM-P synthesis. The authors would like to thank Dr. Cesar Laia for his help with the flash-flow setup and fruitful discussions. The authors would like to acknowledge Fundacao para a Ciencia e Tecnologia for A. Vidal Pinheiro scholarship SFRH/BD/24276/2005.
Amer chemical soc
Washington