EFFECT OF AQUEOUS ENVIRONMENT ON TAUTOMERIZATION OF BIOMOLECULES THROUGH CATIONS - A MNDO STUDY

Barrier heights for deprotonation of certain atomic sites of cations o f N-methyl formamide, N-methyl thioformamide, adenine and guanine lead ing to formation of one or the other neutral tautomeric forms of the m olecules were studied using the MNDO molecular orbital method. Effects of the aqueous environment were considered by including two water mol ecules coupling the protonated sites. It is found that the barrier hei ght would be lowered appreciably due to the aqueous environment. The b arrier heights are different in the different cases, lying between app roximately 0.5 and 1.8 eV.