Biopolym. Cell. 1992; 8(1):51-56.
Structure and Function of Biopolymers
Isocytosine tautomerism in solution
1Pivovarov V. B., 1Sheina G. G.
  1. B. I. Verkin Institute for Low Temperature Physics and Engineering, NAS of Ukraine
    47, Prospekt Lenina, Kharkiv, Ukraine, 61103

Abstract

Studies on temperature changes in vibrational spcctra of aqueous solutions of isocytosine (i-Cyt) and its model compounds in the range from 23 °C to 98 °C are aimed at revealing rare tautomeric forms of i-Cyt in solutions and at clearing up physicochemical conditions of their existence. IR-spectra of methanol solutions of the above compounds are obtained. Spectral analysis and comparison between results obtained and literature data allow to conclude that tautomeric equilibrium of i-Cyt is of keto-amine – keto-imine type. The supposition of the energetic advantage of the existence of the tautomer with lesser dipole moment due to the lesser polar environment gives and argument for the increase of the rare imine form concentration at the increase of the solution temperature

References

[1] Saenger W. Principles of nucleic acid structure. New York: Springer, 1984; 556 p.
[2] Radchenko ED, Sheina GG, Smorygo NA, Blagoi YP. Experimental and theoretical studies of molecular structure features of cytosine. J Mol Struct. 1984;116(3-4):387–96.
[3] Stepanian SG, Sheina GG, Radchenko ED, Blagoi YuP. Infrared spectra and tautomerism isocytosine in an argon matrix. Zh Fiz Khim. 1989; 63(11):3008-14.
[4] Stepanian SG, Radchenko ED, Sheina GG, Blagoi YP. MNDO and IR spectroscopic studies of tautomerism of isocytosine. J Mol Struct. 1990;216:77–90.
[5] Tsuchiya Y, Tamura T, Fujii M, Ito M. Keto-enol tautomer of uracil and thymine. J PhysChem. 1988;92(7):1760–5.
[6] Dreyfus M, Bensaude O, Dodin G, Dubois JE. Tautomerism in cytosine and 3-methylcytosine. A thermodynamic and kinetic study. J Am Chem Soc. 1976;98(20):6338-49.
[7] Dreyfus M, Dodin G, Bensaude O, Dubois JE. Tautomerism of purines. 2. Amino-imino tautomerism in 1-alkyladenines. J Am Chem Soc. 1977;99(21):7027-37.
[8] Semenov SG, Tulub AA, Stesenko AI, Skaletskiy EK. Quantum chemical and UV spectroscopic study isocytosine. Zh Obshch Khim. 1988; 58(4):901-5.
[9] Tulub AA, Semenov SG, Stetsenko AI, Yudovich EE. Spectroscopic and quantum chemical studies of isocytosine. Theor Exp Chem. 1988;24(1):26–32.
[10] Sharma BD, McConnell JF. The crystal and molecular structure of isocytosine. Acta Crystallogr. 1965;19(5):797-806.
[11] Yakovlev KI, Stetzenko AI, Tulub AA et al Platinum (II) complexes with aminopyrimidines. 5th Int. symp. on platinum and other coordination compounds in cancer chemotherapy (Padua, 29June- 2 Jul. 1987). Padua, 1987: 361-2.
[12] Bellamy LJ. The infra-red spectra of complex molecules. London : Methuen New York : Wiley, 1958.
[13] Böhm S, Venyaminov SYu, Fabian H, Filimonov VV, Welfle H. Conserved unpaired adenine residues are important for ordered structures of 5S ribosomal RNA. An infrared study of the secondary and tertiary structure of Thermus thermophilus 5S rRNA. Eur J Biochem. 1985;147(3):503-10.