title: Excited-State Dynamics of Melamine and Its Lysine Derivative Investigated by Femtosecond Transient Absorption Spectroscopy.
abstract: Melamine may have been an important prebiotic information carrier, but its excited-state dynamics, which determine its stability under UV radiation, have never been characterized. The ability of melamine to withstand the strong UV radiation present on the surface of the early Earth is likely to have affected its abundance in the primordial soup. Here, we studied the excited-state dynamics of melamine (a proto-nucleobase) and its lysine derivative (a proto-nucleoside) using the transient absorption technique with a UV pump, and UV and infrared probe pulses. For melamine, the excited-state population decays by internal conversion with a lifetime of 13 ps without coupling significantly to any photochemical channels. The excited-state lifetime of the lysine derivative is slightly longer (18 ps), but the dominant deactivation pathway is otherwise the same as for melamine. In both cases, the vast majority of excited molecules return to the electronic ground state on the aforementioned time scales, but a minor population is trapped in a long-lived triplet state.
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. yuyuan.zhang@montana.edu.
authors.forename: Yuyuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. ashleya1117@gmail.com.
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Beckstead
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. huys13@lzu.edu.cn.
authors.forename: Yuesong
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA. piao.6@osu.edu.
authors.forename: Xijun
authors.initials: X
authors.lastname: Piao
authors.affiliation: Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA. bong.6@osu.edu.
authors.forename: Dennis
authors.initials: D
authors.lastname: Bong
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA. kohler.40@osu.edu.|Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA. kohler.40@osu.edu.
authors.forename: Bern
authors.initials: B
authors.lastname: Kohler
mesh_terms: D004355:Drug Stability; D007700:Kinetics; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry*; D056692:Prebiotics; D011789:Quantum Theory; D013816:Thermodynamics; D014227:Triazines / Q000737:chemistry*
chemical_list: D056692:Prebiotics; D014227:Triazines; D008239:Lysine; C011907:melamine
keywords: UV photostability; prebiotic molecules; s-triazines; time-resolved vibrational spectroscopy