Formation of a protein-bound pyrazinium free radical cation during glycation of histone H1

Georg T. Wondrak, Sridhar Varadarajan, D. Allan Butterfield, Myron K. Jacobson

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Glycation, the nonenzymatic reaction between protein amino groups and reducing sugars, induces protein damage that has been linked to several pathological conditions, especially diabetes, and general aging. Here we describe the direct identification of a protein-bound free radical formed during early glycation of histone H1 in vitro. Earlier EPR analysis of thermal browning reactions between free amino acids and reducing sugars has implicated the sugar fragmentation product glycolaldehyde in the generation of a 1,4-disubstituted pyrazinium free radical cation. In order to evaluate the potential formation of this radical in vivo, the early glycation of BSA, lysozyme, and histone H1 by several sugars (D-glucose, D-ribose, ADP-ribose, glycolaldehyde) under conditions of physiological pH and temperature was examined by EPR. The pyrazinium free radical cation was identified on histone H1 glycated by glycolaldehyde (g = 2.00539, a(N) = 8.01 [2N], a(H) = 5.26 [4H], a(H) = 2.72 [4H]), or ADP-ribose. Reaction of glycolaldehyde with poly- L-lysine produced an identical signal, whereas reaction with BSA or lysozyme produced only a minor unresolved singlet signal. In the absence of oxygen the signal was stable over several days. Our results raise the possibility that pyrazinium radicals may form during glycation of histone H1 in vivo. (C) 2000 Elsevier Science Inc.

Original languageEnglish
Pages (from-to)557-567
Number of pages11
JournalFree Radical Biology and Medicine
Issue number6
StatePublished - Sep 15 2000

Bibliographical note

Funding Information:
This research was supported by National Institutes of Health Grants CA43894 and NS38496.


  • ADP-ribose
  • Electron paramagnetic resonance
  • Free radicals
  • Glutathione
  • Glycation
  • Glycolaldehyde
  • Histone H1
  • Pyrazinium free radical

ASJC Scopus subject areas

  • Biochemistry
  • Physiology (medical)


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