Side chain fragmentation of N-terminal threonine or serine residue induced through intramolecular proton transfer to hydroxy sulfuranyl radical formed at neighboring methionine in dipeptides

Journal Article · Wed Jun 01 00:00:00 EDT 1994 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00090a012· OSTI ID:7019489

Schoeneich, C; Zhao, F ^[1]; Madden, K P; Bobrowski, K ^[2]

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1. Univ. of Kansas, Lawrence, KS (United States)
2. Univ. of Notre Dame, IN (United States)

The reaction of hydroxyl radicals with Ser-Met and Thr-Met at slightly acidic to neutral pH results in the side chain fragmentation of the Ser and the Thr moiety into formaldehyde and acetaldehyde, respectively. The efficiency of this process depends on the concentration of the peptide and protons with maximum yields at low peptide concentrations at near neutral pH. Significantly less aldehyde formation is observed for the reaction of hydroxyl radicals with Ala-Met, Val-Met, Gly-Ser-Met, Met-Ser, Gly-Met-Ser, Ser-Leu, Gly-Thr-Met, and Gly-Met-Thr. These results indicate that the formation of aldehyde requires (i) an N-terminal Ser or Thr residue and (ii) the presence of Met in the sequence. The underlying mechanism involves an intramolecular proton transfer from the protonated N-terminal amino group to an initially formed hydroxy sulfuranyl radical at the Met residue. This process leads to the elimination of water and the simultaneous formation of a three-electron-bonded [>S[therefore]NH[sub 2]][sup +]-peptide intermediate which absorbs at [lambda][sub max] = 385 nm and has been identified by pulse radiolysis. This intermediate decays with t[sub 1/2] = 310 ns into aldehyde and an [alpha]-amino radical of the structure H[sub 2]N-C[sup [sm bullet]]H-C(= O)NH-peptide, which has been identified by ESR spectroscopy. 57 refs., 8 figs.

• OSTI ID: 7019489
• Journal Information: Journal of the American Chemical Society; (United States), Vol. 116:11; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
HYDROXYL RADICALS
CHEMICAL REACTIONS
PEPTIDES
ACETALDEHYDE
AMINO ACIDS
CHROMATOGRAPHY
ELECTRON BEAMS
ELECTRON SPIN RESONANCE
FORMALDEHYDE
GAMMA RADIATION
METHIONINE
OXIDATION
PH VALUE
REACTION INTERMEDIATES
SERINE
THREONINE
ALDEHYDES
BEAMS
CARBOXYLIC ACIDS
DRUGS
ELECTROMAGNETIC RADIATION
HYDROXY ACIDS
IONIZING RADIATIONS
LEPTON BEAMS
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PARTICLE BEAMS
PROTEINS
RADIATIONS
RADICALS
RESONANCE
SEPARATION PROCESSES
400201* - Chemical & Physicochemical Properties
400600 - Radiation Chemistry
400102 - Chemical & Spectral Procedures