STRUCTURES AND ENERGETIC PROPERTIES OF B-DNA NUCLEOTIDES

A density functional study is carried out for the B-DNA nucleotides ad enine, thymine, cytosine, and guanine and some of their modifications (tautomeric and methylated forms). The local spin density method is ap plied to find gas-phase structures. Gradient corrections for exchange and correlation terms are included to compute energetic features such as total, nonlocal, interaction, and reorganization energies. Special attention is paid to the relative stabilities among naturally occurrin g nucleotides and some tautomeric forms. Structural stability and flex ibility in terms of reorganization and interaction energies, of concer n in selective and mutation processes, is also discussed for nucleic a cid bases of different nucleotides.