title: [A theoretical investigation of tautomerism of adenine, purine, guanine, and cytosine].
abstract: The parameters of tautomeric equilibrium and stability of lactam-lactim, amino-imino, and N9H <--> N7H tautomeric forms of adenine, purine, guanine, and cytosine for isolated states have been calculated. It was found that the Ade-N9H tautomeric form is most stable; in this case the intramolecular proton transfer and tautomeric transformation Ade-N9H --> Ade-N7H can occur. The parameters of tautomeric equilibrium and stability for seven tautomeric forms of guanine were determined. For cytosine, the simultaneous existence of the amino-hydroxy, imino-oxo and valence amino-hydroxy of tautomeric forms was predicted.
authors.forename: G N
authors.initials: GN
authors.lastname: Ten
authors.forename: V I
authors.initials: VI
authors.lastname: Baranov
mesh_terms: D000225:Adenine / Q000737:chemistry*; D003596:Cytosine / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D008956:Models, Chemical; D011687:Purines / Q000737:chemistry*
chemical_list: D011687:Purines; D006147:Guanine; D006859:Hydrogen; D003596:Cytosine; D000225:Adenine; C030985:purine