Millisecond radiolytic modification of peptides by synchrotron X-rays identified by mass spectrometry

Simin D. Maleknia, Michael Brenowitz, Mark R. Chance

Research output: Contribution to journalArticlepeer-review

200 Scopus citations


Radiolysis of peptide and protein solutions with high-energy X-ray beams induces stable, covalent modifications of amino acid residues that are useful for synchrotron protein footprinting. A series of 5-14 amino acid residue peptides of varied sequences were selected to study their synchrotron radiolysis chemistry. Radiolyzed peptide products were detected within 10 ms of exposure to a white light synchrotron X-ray beam. Mass spectrometry techniques were used to characterize radiolytic modification to amino acids cysteine (Cys), methionine (Met), phenylalanine (Phe), tyrosine (Tyr), tryptophan (Trp), proline (Pro), histidine (His), and leucine (Leu). A reactivity order of Cys, Met >> Phe, Tyr, > Trp > Pro > His, Leu was determined under aerobic reaction conditions from MS/MS analysis of the radiolyzed peptide products. Radiolysis of peptides in 18O-labeled water under aerobic conditions revealed that oxygenated radical species from air and water both contribute to the modification of amino acid side chains. Cysteine and methionine side chains reacted with hydroxyl radicals generated from radiolysis of water as well as molecular oxygen. Phenylalanine and tyrosine residues were modified predominantly by hydroxyl radicals, and the source of modification of proline was exclusively through molecular oxygen.

Original languageEnglish (US)
Pages (from-to)3965-3973
Number of pages9
JournalAnalytical Chemistry
Issue number18
StatePublished - Sep 15 1999

ASJC Scopus subject areas

  • Analytical Chemistry


Dive into the research topics of 'Millisecond radiolytic modification of peptides by synchrotron X-rays identified by mass spectrometry'. Together they form a unique fingerprint.

Cite this