Variation of Nonexchangeable Proton Resonance Chemical Shifts as a Probe of Aberrant Base Pair Formation in DNA

Lawrence C. Sowers, G. Victor Fazakerley, Hyun Kim, Larry Dalton, Myron F. Goodman

Research output: Contribution to journalArticle

53 Scopus citations

Abstract

Variation of nonexchangeable proton resonance chemical shifts for deoxycytidine and deoxyadenosine as a function of protonation and imino tautomer formation has been determined. Protonation induces downfield shifts of proton resonances whereas formation of the rare imino tautomer induces upfield shifts. Titration curves are constructed on the basis of spectrophotometrically determined pK values. Excellent fit is obtained between theoretical titration curves and experimental data, which indicates that chemical shifts of base protons may be used to quantitatively determine the relative concentrations of either rare imino tautomeric conformations or protonated base forms. These data may be utilized as an aid in the elucidation of the nature of hydrogen bonding between mismatched base pairs in DNA oligomers containing cytosine or adenine residues. These data, in conjunction with the oligonucleotide study of Patel et al. [Patel, D. J., Kozlowski, S. A., Ikuta, S., & Itakura, K. (1984) Biochemistry 23, 3218-3226], have been used to rigorously argue the existence of a "protonated" adenine residue in the A-C mismatch. This structure allows reconciliation of the NMR solution data with crystallographic data [Hunter, W. N., Brown, T., Anand, N. N., & Kennard, O. (1986) Nature (London) 320, 552-555], which support the protonated base pair.

Original languageEnglish (US)
Pages (from-to)3983-3988
Number of pages6
JournalBiochemistry
Volume25
Issue number14
DOIs
StatePublished - Jul 1986
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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