Mechanism of production of hydroxyl radicals in the copper-catalyzed oxidation of dithiothreitol.
We have undertaken detailed studies of the mechanisms involved in the production of OH radicals during the copper-catalyzed oxidation of dithiothreitol (DTT). Most of these studies were conducted in real time, detecting .OH based on its reaction with coumarin-3-carboxylic acid to produce the fluorescent derivative 7-hydroxycoumarin-3-carboxylic acid (7-OHCCA). Studies of the kinetics of oxidizing DTT show that production of .OH occurs in two stages: an initial lag period during which there is little production of 7-OHCCA, and a second reaction phase during which there is more rapid generation of .OH. The duration of the initial reaction period depends on the concentrations of both DTT and Cu2+. During this initial stage, oxygen consumption is high, although an increasing concentration of Cu2+ decreases the oxygen consumption. The rate of production of .OH during the second phase of the reaction depends on the concentration of Cu2+, but little oxygen is consumed. A mechanism is proposed whereby a Cu2+-DTT complex is formed and catalyzes oxidation of free DTT via formation of an oxygen-containing intermediate. The second phase of the reaction begins after complete oxidation of free DTT and involves production of O2.- and H2O2 followed by generation of .OH via reduction of H2O2 by cuprous ion.
Kachur
A V
AV
Department of Radiation Oncology, University of Pennsylvania, Philadelphia 19104, USA.
Held
K D
KD
Koch
C J
CJ
Biaglow
J E
JE
D003300:Copper; D003374:Coumarins; D004229:Dithiothreitol / Q000737:chemistry*; D017665:Hydroxyl Radical; D007700:Kinetics; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010100:Oxygen
D003374:Coumarins; D017665:Hydroxyl Radical; D003300:Copper; D010100:Oxygen; D004229:Dithiothreitol