Density Functional Theory Investigation Of Hyperfine Interaction In Dna Nucleobase And Nucleotide Muoniated Radicals

Density Functional Theory method at B3LYP/6-311++G(d,p) level of theory was successfully applied to investigate the structure, energy, and associated muonium hyperfine coupling constant of radicals produced by muonium addition to DNA nitrogenous bases (guanine, adenine, cytosine, and thymine) in nucleobase and nucleotide forms. Based on DFT total energy, the lowest energy Mu sites in nucleobase and nucleotide are the same: guanine (C8); adenine (C8 < N2); cytosine (N3 < C5 < C6); and thymine (C6 < C5 < 04). The values of isotropic Fermi contact coupling constant, A(iso) in purine bases does not change significantly in going from nucleobase to nucleotide system. However, muonium A(iso) for pyrimidine bases is greatly affected by changing methyl to sugar phosphate. For O4 site in thymine, the sign of muonium A(iso) changes from negative in nucleobase to positive in nucleotide, indicating a negation in the muonium Is electron spin polarization effect.