Photostability of 2,6-diaminopurine and its 2′-deoxyriboside investigated by femtosecond transient absorption spectroscopy

Abstract

Ultraviolet radiation (UVR) from the sun is essential for the prebiotic syntheses of nucleotides but it can also induce photolesions such as the cyclobutane pyrimidine dimers (CPDs) to RNA or...

The copious photochemistry of 2,6‐diaminopurine: Luminescence, triplet population, and ground state recovery*

“…The 7H-26DAP photorelaxation mechanisms were only investigated previously at the TD-BP86/CPCM(water)/ def2-TZVP//TD-B3LYP/cc-pVDZ level of theory, 18 concluding that the 7H-C6-puckered S1/GS state crossing region (~0.06 eV below the FC region) can be accessed barrierlessly from the Franck-Condon region, in contrast to the path towards the 7H-C2-puckered structure (at about the same energy of the FC region) which exhibits a barrier of 0.8 eV. Our MS-CASPT2 results suggest a deeper minimum on the 7H-26DAP tautomer 1 (ππ* L a ) potential energy hypersurface.…”

Electronic relaxation mechanism of 9‐methyl‐2,6‐diaminopurine and 2,6‐diaminopurine‐2′‐deoxyribose in solution

“…In a recent investigation, the excited state dynamics of 2,6DAP and 2,6DAP-d were examined in aqueous solution. 15 It was proposed that the excited state population in the Franck-Condon region of the S 1 (ππ* L a ) state also branches in ultrafast timescales via the C2-and C6puckering relaxation coordinates following excitation at 287 nm. 15 Herein, we have also identified both coordinates for 9Me2,6DAP-d. On the one hand, we propose that in 9Me2,6DAP and 2,6DAP-d, the population following the C6-coordinate internally converts to the ground state in an ultrafast fashion considering the small energy barrier (<0.1 eV) associated with the C6-CI.…”

“…15 It was proposed that the excited state population in the Franck-Condon region of the S 1 (ππ* L a ) state also branches in ultrafast timescales via the C2-and C6puckering relaxation coordinates following excitation at 287 nm. 15 Herein, we have also identified both coordinates for 9Me2,6DAP-d. On the one hand, we propose that in 9Me2,6DAP and 2,6DAP-d, the population following the C6-coordinate internally converts to the ground state in an ultrafast fashion considering the small energy barrier (<0.1 eV) associated with the C6-CI. On the other hand, we propose that the fraction of the population that branches into the C2-coordinates decays by a combination of internal conversion through the C2-CI and radiative decay due to the associated larger energy barrier (0.35 eV) to access the C2-CI.…”

“…[31][32][33] In a recent study, the electronic relaxation mechanisms of 2,6DAP and 2,6-diaminopurine-2′-deoxyribose (2,6DAP-d) were investigated in aqueous solutions. 15 It was proposed that 2,6DAP could have accumulated in large enough quantities during the prebiotic era due to its high photostability. 15 Those results support the notion that 2,6DAP may have been involved in the formation of prebiotic oligomers, acting as photoprotective components for the prebiotic genetic code and potentially enhancing the photostability of higher-order nucleic acid structures.…”

“…15 It was proposed that 2,6DAP could have accumulated in large enough quantities during the prebiotic era due to its high photostability. 15 Those results support the notion that 2,6DAP may have been involved in the formation of prebiotic oligomers, acting as photoprotective components for the prebiotic genetic code and potentially enhancing the photostability of higher-order nucleic acid structures. 29 In this contribution, we extend those investigations by studying the electronic deactivation pathways of 2,6DAP-d and 9-methyl-2,6-diaminopurine (9Me2,6DAP) in acetonitrile (MeCN) and in phosphate buffer solution at pH 7.4.…”