Peptide cysteine thiyl radicals abstract hydrogen atoms from surrounding amino acids: the photolysis of a cystine containing model peptide.
Peptide cysteine thiyl radicals were generated through UV-photolysis of disulfide precursors, in order to follow intramolecular reactions of those radicals with neighboring amino acids. When reactions were carried out in D(2)O, there was a significant incorporation of deuterium specifically into the C(alpha)-H bonds of glycine residues in positions i+1 and i-1 to the Cys residue, indicating a fast reversible H-atom transfer. This H-atom transfer occurred prior to the formation of final, nonradical products including free thiol, thioaldehyde, and aldehyde. Such fast H-atom transfer is relevant to biologic conditions of oxidative stress and to the stabilization of proteins against oxidation, where the formation of carbon-centered radicals in proteins may lead to fragmentation, intramolecular cross-linking, aggregation and/or epimerization.
Mozziconacci
Olivier
O
The Department of Pharmaceutical Chemistry, 2095 Constant Avenue, University of Kansas, Lawrence, Kansas 66047, USA.
Sharov
Victor
V
Williams
Todd D
TD
Kerwin
Bruce A
BA
Schöneich
Christian
C
D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000737:chemistry*; D003553:Cystine / Q000737:chemistry*; D041961:Deuterium Exchange Measurement; D004220:Disulfides / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D010782:Photolysis; D021241:Spectrometry, Mass, Electrospray Ionization; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry
D004220:Disulfides; D010455:Peptides; D003553:Cystine; D006859:Hydrogen; D003545:Cysteine