Long range electron transfer between tyrosine and tryptophan in hen egg-white lysozyme

Marcelo Weinstein, Zeev B. Alfassi, Michael R. DeFelippis, Michael H. Klapper, M. Faraggi

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


The azide, dibromide and dichloride radicals oxidize one or more tryptophan side chains in hen egg-white lysozyme. The indolyl radical produced in this second-order 1-electron oxidation subsequently oxidizes a tyrosine side chain to the phenoxy radical in an intramolecular reaction with a rate constant of 130±10 s-1 at pH 7, 25°C. The final indolyl and phenoxy equilibrium mixture then decays with a t 1 2≈ s. The faster intramolecular reaction exhibits a pH dependence; on decreasing the pH from 9 the first-order rate constant increases to a maximum near pH 5.4 and then declines as the pH is lowered further. In contrast, the first-order rate constant for the intramolecular electron transfer between the tyrosine and tryptophan of the peptide trpH-pro-tyrOH remains unchanged between approx. pH 11 and 6.5 and then increases as the pH is lowered further. This difference in the observed pH dependence suggests that changes in structure or ionization state influence the protein electron transfer rate. We also discuss the radiation inactivation of lysozyme in light of these observations.

Original languageEnglish
Pages (from-to)173-178
Number of pages6
JournalBiochimica et Biophysica Acta - Proteins and Proteomics
Issue number2
StatePublished - 29 Jan 1991


  • (Hen egg-white)
  • Electron transfer
  • Intramolecular reaction
  • Lysozyme
  • Protein dynamics

ASJC Scopus subject areas

  • Molecular Biology
  • Structural Biology
  • Biophysics
  • Biochemistry


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