Ab initio study of the structure of isocytosine–cytosine standard Watson–Crick base pairs in the gas phase and in water

✍ Scribed by N. U. Zhanpeisov; J. Leszczynski

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 587 KB
• Volume: 69
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1998)69:1<37::aid-qua6>3.0.co;2-y

✦ Synopsis

Ab initio quantum chemical studies at the HF and MP2 levels with the 6-31G U basis set were performed for H-bonded isocytosine᎐cytosine standard Ž . Watson᎐Crick base pairs denoted as iCC1 in the gas phase and in a water solution. Full geometry optimizations at the HF level without any constraints on the planarity of these complexes were carried out. The water solution was modeled by the explicit inclusion of one, two, four, and six water molecules. Six waters create the first full coordination sphere around the iCC1 base pair. All potentially possible hydration positions of the iCC1 base pair with one and two water molecules were considered. The interaction and solvation energies were corrected for the basis-set superposition error by using the full Boys᎐Bernardi counterpoise correction scheme. It was shown that inclusion of six instead of one, two, or four water molecules has a crucial effect on the geometry of the iCC1 base pair. In the case of six water molecules, the iCC1 moiety becomes strongly nonplanar,