Mechanism of 4-carboxybenzophenone-sensitized photooxidation of methionine-containing dipeptides and tripeptides in aqueous solution

Journal Article · Thu Sep 07 04:00:00 EDT 1995 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100036a037· OSTI ID:106778

Marciniak, B ^[1]; Hug, G L ^[1]; Bobrowski, K ^[2]; Kozubek, H ^[3]

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1. Univ. of Notre Dame, IL (United States)
2. Inst, of Nuclear Chemistry and Technology, Warsaw (Poland)
3. A. Mickiewicz Univ., Poznan (Poland)

The mechanism of 4-carboxybenzophenone (CB)-sensitized photooxidation of methionine-containing dipeptides (Met-Gly and Gly-Met) and tripeptides (Met-Gly-Gly, Gly-Met-Gly, and Gly-Gly-Met) was investigated using nanosecond flash photolysis and steady-state photolysis. The rate constants for quenching of the CB triplet by sulfur-containing peptides were determined to be in the range (1.8-2.3) x 10{sup 9} M{sup -1} S{sup -1} for neutral and alkaline solutions. The presence of the various electron-transfer intermediates accompanying the CB triplet quenching events was identified through the use of a multiple-regression procedure that was used to resolve the experimental transient spectra into components. The intermediates identified were the CB ketyl radical anion, the CB ketyl radical, intermolecularly (S.{sup {center_dot}}.S)-bonded radical cations, and intramolecularly (S.{sup {center_dot}}.N)-bonded radical cations derived from peptides. The types of intermediates were found to depend on the pH of the solution and on the location of the methionine unit with respect to the terminal functions. The quantum yields of all the transients and the kinetics of their formation and decay were measured by flash photolysis, and quantum yields of CO{sub 2} formation were measured by steady-state photolysis. 50 refs., 6 figs., 3 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 106778
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 36 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
55 BIOLOGY AND MEDICINE
BASIC STUDIES
ABSORPTION SPECTRA
AQUEOUS SOLUTIONS
BIOCHEMISTRY
CARBONYLS
ELECTRON TRANSFER
ORGANIC COMPOUNDS
OXIDATION
PEPTIDES
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
REACTION INTERMEDIATES