珍贵三环核苷衍生物的理论计算与实验研究

Theoretical calculation and experimental studies of rare tricyclic nucleoside derivative

N-4-desmethylwyosine (dYt), a derivative of rare tricyclic nucleosides is probably a new member of Y-nucleosides found in tRNA [1]. The structure of dYt has tricyclic ring with rigid conformation and high electron delocalization. Both the absorption and emission bands of dYt are well separated from normal bases, so it could probably be used as an effective natural fluorescent probe to study RNA structure and sequence[2].Fig.1 The secondary structure of yeast tRNAPbe anticodon loop and molecular structures ofguanosine and N-4-desmethylwyosine An ab initio study was performed to evaluate stability of three isomers of this compound. Ionization potential (IP) of dYt was calculated. It was found that the value was lower than that of guanosine and guanine. This shows that dYt loses electron more easily than guanine.In addition, the result has been verified by experimental studies performed by nanosecond laser photolysis.The reactions of dYt and a series of transient species such as reduction radicals eaq-, H· and oxidation radicals ·OH,SO4·-, CO3·- and N3· have been carried out by nanosecond pulse radiolysis. Rate constants of these reactions have been determined and related mechanisms were discussed.