Theoretical Study of the Proton Transfer of Uracil and(Water),,(n=0-4): Water Stabilization and Mutagenicity for Uracil

摘要

To investigate the tautomerism of uracil-(water)_n(n=0-4)that is induced by proton transfer,we describe a study of structural tautomer interconversion and the relative stabilizing influences of water on uracil(U)and its enol form(U~*),using density functional theory(DFT)calCl_4lations by means of the B3LYP exchange and correlation functions.Thirty-three geometries,including seven significant transition states,were optimized,and their geometrical parameters have been disCl_4ssed in detail.Water moleCl_4les have been gradually placed in different regions in the vicinity of U and U~*,and the intramoleCl_4lar interactions between U,U~*,and water moleCl_4les have been studied.The relative stabilities of all tautomers were established.The calCl_4lated results indicate that there are two absolutely opposite regions in the vicinity of uracil.In one of the regions,water moleCl_4les can protect U from tautomerizing to U~*,whereas in another region,water moleCl_4les can assist the tautomerism from U to U~*.The stabilization and mutagenicity effects of increasing the number of water moleCl_4les in only one region and in both regions have been systematically studied and disCl_4ssed.