Nitrogen chemical structure in DNA and related molecules by X-ray absorption spectroscopy

Sudipa Mitra Kirtley*, Oliver C. Mullins, Jie Chen, Jan van Elp, Simon J. George, C. T. Chen, Thomas O'Halloran, Stephen P. Cramer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


The electronic environment of nitrogen in nucleic acid bases, nucleotides, polynucleotides and DNA has been studied, for the first time using X-Ray Absorption Near-Edge Spectroscopy (XANES). Generally, the spectra of these complex molecules consist of low energy bands corresponding to 1s → π* transitions and high energy bands corresponding to 1s → σ* transition, as illustrated using several nitrogen model compounds. The 1s → π* transitions show particular sensitivity to the chemical environment of the nitrogen. Oxygen substitution on ring carbon atoms generally results in a significant blue shift of the lowest 1s → π* bands while halogen substitution results in a small blue shift. These observations illustrate the significance of the disturbance of the aromatic ring system produced by exocyclic carbonyl groups. Direct substitution on the nitrogen frequently results in significant spectral perturbations. Differences between the spectra of the polynucleotides and the sums of spectra of the individual nucleotides point to the effects of hydrogen-bonding in complementary double-helix structures. The XANES spectrum of a DNA sample with a known ratio of the polynucleotides is equivalent to the weighted sum of the spectra of individual polynucleotides, indicating that the difference in base stacking interactions produces negligible spectral effects. The variability of nitrogen K-edge spectra in these samples and in protein may be useful for chemically specific imaging using X-ray microscopes.

Original languageEnglish (US)
Pages (from-to)249-254
Number of pages6
JournalBBA - Gene Structure and Expression
Issue number3
StatePublished - Oct 20 1992


  • DNA structure
  • Hydrogen bonding
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

  • Structural Biology
  • Biophysics
  • Biochemistry
  • Genetics


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