USE OF MOLECULAR ANALOGS FOR THE BASES IN DNA - STABILITY OF MOLECULAR PAIRS IN GAS-PHASE AND AQUEOUS-MEDIA AND POSSIBLE ROLE OF HYDROGEN-BONDING

In a recent experimental study, it was reported that replacement of th ymine in the adenine-thymine base pair of DNA by its molecular analogs which cannot form proper hydrogen bonds with adenine (A) does not cau se disruption of DNA structure and synthesis. AM1 and ab initio molecu lar orbital calculations and electric field mapping were carried out i n order to examine the possibility of pairing of A with each one of tw o analogs of thymine in the gas phase. Self-consistent reaction field calculations were also carried out on the individual molecules and the ir pairs using the polarized continuum model in order to examine their stability in aqueous media. Our results are broadly in agreement with the conclusions drawn in the above-mentioned experimental work. (C) 1 998 John Wiley & Sons, Inc.