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

The photophysics and electronic relaxation mechanism of 2,6-diaminopurine-2 ′-deoxyribose and 9-methyl-2,6-diaminopurine is experimentally and computationally investigated in acetonitrile and aqueous solution. The relaxation mechanism includes deactivation through C2- and C6-reaction coordinates and involves two conical intersections. Longer lifetimes are observed in aque ous solution than in acetonitrile and trapping of the population in the S1( ππ*) is more efficient in 2,6-diaminopurine-2′-deoxyribose than in 9-methyl-2,6-diaminopurine. Collectively, it is demonstrated that prebiotic 2,6-diaminopurine could have accumulated in significant quantities during the prebiotic era to be incorporated into non-canonical RNA and play a signific ant role in the photoprotection of primitive nucleic acids. AbstractProlonged ultraviolet exposure results in the formation of cyclobutane pyrimidine dimers (CPDs) in RNA. Consequently, prebiotic photolesion repair mechanisms should have played an important role in the maintenance of the structural integrity of primitive nucleic acids. 2,6-Diaminopurine is a prebiotic nucleobase that repairs CPDs with high efficiency when incorporated into polymers. We investigate the electronic deactivation pathways of 2,6-diaminopurine-2 ′-deoxyribose and 9-methyl-2,6-diaminopurine in acetonitrile and aqueous solution to shed light on the photophysical and excited state properties of the 2,6-diaminopurine chromophore. Evidence is presented that both...
Source: Photochemistry and Photobiology - Category: Science Authors: Tags: SPECIAL ISSUE RESEARCH ARTICLE Source Type: research