Electron correlation effects in the ab initio study on tautomerism of guanine

✍ Scribed by Jerzy Leszczyński

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 603 KB
• Volume: 174
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(90)85357-i

✦ Synopsis

The molecular structures of three guanine tautomers are examined using ab initio method at the MP2/6-31G**//HF/6-3 IG level. The study predicts amino-oxo Gua N( 7)H tautomer (1) to be the global minimum. The second amino-ox0 Gua N( )H (2) and amino-hydroxy Gus* N(9)H (3) tautomers have relative energies of 0.5 an 4.6 kJ mol-' (MP2/6-3IG** tZPE), respectively. These results explain well recent experimental IR matrix-isolation and UV photoelectron studies on guanine. The shift of tautomeric equilibria towards 2 on going from the isolated molecules towards polar solvents is predicted. The influence of the basis set and electron correlation contributions on the relative energies of tautomers is discussed.