PMID: 8604298Feb 15, 1996Paper

Acid-induced exchange of the imino proton in G.C pairs

Nucleic Acids Research
S NoninM Guéron

Abstract

Acid-induced catalysis of imino proton exchange in G.C pairs of DNA duplexes is surprisingly fast, being nearly as fast as for the isolated nucleoside, despite base-pair dissociation constants in the range of 10(-5) at neutral or basic pH. It is also observed in terminal G.C pairs of duplexes and in base pairs of drug-DNA complexes. We have measured imino proton exchange in deoxyguanosine and in the duplex (ATATAGATCTATAT) as a function of pH. We show that acid-induced exchange can be assigned to proton transfer from N7-protonated guanosine to cytidine in the open state of the pair. This is faster than transfer from neutral guanosine (the process of intrinsic catalysis previously characterized at neutral ph) due to the lower imino proton pK of the protonated form, 7.2 instead of 9.4. Other interpretations are excluded by a study of exchange catalysis by formiate and cytidine as exchange catalysts. The cross-over pH between the regimes of pH-independent and acid-induced exchange rates is more basic in the case of base pairs than in the mononucleoside, suggestive of an increase by one to two decades in the dissociation constant of the base pair upon N7 protonation of G. Acid-induced catalysis is much weaker in A.T base pairs, as ...Continue Reading

Citations

Jun 3, 2009·Journal of the American Chemical Society·Jonathan FarjonBernhard Brutscher
Oct 16, 2001·Nucleic Acids Research·L Jiang, I M Russu
Jun 21, 2011·Artificial DNA, PNA & XNA·Maxim D Frank-Kamenetskii
Sep 6, 2011·The Journal of Physical Chemistry. B·Yuexia LinHenry F Schaefer
May 2, 1997·Journal of Molecular Biology·S NoninD J Patel
Dec 19, 2020·Nucleic Acids Research·Ayako FurukawaKenji Sugase
Oct 24, 2001·Inorganic Chemistry·Franck LegendreJean-Claude Chottard

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