Prototropic tautomers of 5-methylcytosine and enthalpy changes of their protonation, deprotonation, and deamination: Hybrid density functional B3LYP study

Nicolaides, CA

dc.contributor.author	Nicolaides, CA	en
dc.date.accessioned	2014-03-01T01:51:57Z
dc.date.available	2014-03-01T01:51:57Z
dc.date.issued	2002	en
dc.identifier.issn	00207608	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/26514
dc.subject	5-methylcytosine	en
dc.subject	Enthalpy	en
dc.subject	Hybrid density functional	en
dc.subject	Nucleic acid bases	en
dc.subject	Prototropic tautomerism	en
dc.subject.other	Calculations	en
dc.subject.other	Conformations	en
dc.subject.other	Enthalpy	en
dc.subject.other	Ionization	en
dc.subject.other	Molecular dynamics	en
dc.subject.other	Molecular structure	en
dc.subject.other	Molecular vibrations	en
dc.subject.other	Probability density function	en
dc.subject.other	Thermodynamic properties	en
dc.subject.other	Deamination	en
dc.subject.other	Deprotonation	en
dc.subject.other	Hybrid density functional study	en
dc.subject.other	Methylcytosine	en
dc.subject.other	Protonation	en
dc.subject.other	Tautomerism	en
dc.subject.other	Tautomers	en
dc.subject.other	Quantum theory	en
dc.title	Prototropic tautomers of 5-methylcytosine and enthalpy changes of their protonation, deprotonation, and deamination: Hybrid density functional B3LYP study	en
heal.type	journalArticle	en
heal.identifier.primary	10.1002/qua.10185	en
heal.identifier.secondary	http://dx.doi.org/10.1002/qua.10185	en
heal.publicationDate	2002	en
heal.abstract	Molecular and thermodynamic properties such as geometric parameters, dipole moments, vibrational frequencies, the first ionization potentials, relative tautomerization energies, and tautomeric equilibrium constants of all prototropic tautomers of 5-methylcytosine have been studied at the hybrid density functional level B3LYP/6-31+G(d, p). The methylation on the C5 atom does not lead to significant geometric deformation of the pyrimidine structures of the corresponding tautomers of cytosine, which maintains the similar stability order. The tautomeric species 2-oxo-4-amino [T(0)], 2-hydroxy-4-amino [T(1-2s) and T(1-2t)], and trans-2-oxo-4-imino [T(3-4t)] are predominated in the gas phase. The zwitterionic conformers of tautomerism [T(1-4)] and protonation [P(4), P(1-2s-4), P(1-2t-4), and P(1-3-4)] are investigated for the first time due to their close relationship with deamination during genetic repair. Enthalpy changes (ΔrH) of protonation, deprotonation and deamination are calculated for these tautomeric species at room temperature; it is noted that the relative enthalpies [δ(ΔH)] of the tautomers are rationalized well in terms of a second-order polynomial of the sum of the mean ΔrH values of protonation and deprotonation processes.	en
heal.journalName	International Journal of Quantum Chemistry	en
dc.identifier.doi	10.1002/qua.10185	en
dc.identifier.volume	89	en
dc.identifier.issue	2	en
dc.identifier.spage	106	en
dc.identifier.epage	120	en