A theoretical prediction on the ground-state complexes bound by metal ions to thymine base isomers

摘要

Stability orderings of 150 stable complexes formed by metal ions (Na ~+, K ~+, Ca ~(2+), Mg ~(2+), and Zn ~(2+)) and 13 stable thymine tautomers in both solvent and gas phases are obtained, and the optimal binding site for a metal ion in a specific thymine tautomer is identified. Results indicate that the complex with the canonical thymine tautomer (T1) is more stable than those with the rare ones, and the monodentate complex M-T1o4(o2) are their ground-state form in the solvent phase. The ground-state thymine complexes bound by Ca ~(2+), Mg ~(2+), or Zn ~(2+) become bidentate M-T3o4lo2,n3, which is derived from a rare thymine tautomer T3o4l, whereas those bound by Na ~+ and K ~+ are still monodentate complexes M-T1o4(o2), however, in the gas phase. The differences in stability are discussed in detail from the binding strength of metal ions, relative energy of the corresponding thymine tautomers, and solution effect.