title: [Hydration of complementary 9-methyladenine.1-methyluracil pairs at low temperatures according to data from field mass spectrometry].
abstract: The hydration of nucleotide bases of m9Ade(A), m1Ura(U) and a complementary pair A.U was studied by field ionization mass-spectrometry at room and low (170 K) temperatures in vacuum. Enthalpies of A.U-pair formation and its monohydrate A.U(H2O) were measured using temperature dependences of association constants. From the analysis of intensities of mass-spectrum peaks, corresponding to monohydrates U(H2O), A(H2O), A.U(H2O), A.U-pair and initial components A, U, and also measured enthalpies it is supposed that monohydration of bases A and U essentially prevents the formation of the coplanar pair A.U. A qualitative information about the structure and energetics of hydrate clusters A(H2O)n, U(H2O)n and A.U(H2O)n for n = 1 divided by 7 was obtained from low temperature mass-spectra. The observed peculiarities in hydrate structures A(n = 5), U(n = 4), A.U(n = 4) are treated as a consequence of cyclization of water molecules around bases.
authors.forename: L F
authors.initials: LF
authors.lastname: Sukhodub
authors.forename: A B
authors.initials: AB
authors.lastname: Teplitskiĭ
authors.forename: Iu M
authors.initials: IuM
authors.lastname: Lodianoĭ
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000032:analysis; D001482:Base Composition; D003080:Cold Temperature; D013058:Mass Spectrometry; D013816:Thermodynamics; D014498:Uracil / Q000031:analogs & derivatives* / Q000032:analysis
chemical_list: D014498:Uracil; C002596:1-methyluracil; C013115:9-methyladenine; D000225:Adenine
vernacular_title: Gidratatsiia komplementarnoĭ pary 9-metiladenin.1-metiluratsil pri nizkikh temperaturakh po dannym polevoĭ mass-spektrometrii.