Comparative kinetics of thiol oxidation in two distinct free-radical generating systems: SIN-1 versus AAPH.
To study oxidative stress in biological systems, chemical compounds capable of producing free radicals have been widely used. Here, we compared two free-radical generators, 3-morpholinosydnonimine (SIN-1) and 2,2'-azo-bis(2-amidinopropane) hydrochloride (AAPH), by measuring the thiol oxidation kinetics of various thiols. We found that SIN-1 is > 30 times potent in causing thiol oxidation than AAPH. Kinetic simulations revealed that in the SIN-1 system (0.1 mM), superoxide, nitrogen dioxide and carbonate radicals are the major reactive species which, in combination, induce ∼50% of thiol molecules to undergo one-electron oxidation, thereby forming the thiyl radical which propagates further thiol oxidation by direct coupling with thiolates. Similarly, the alkyl peroxyl radical derived from AAPH (3 mM) initiates comparable extent of one-electron oxidation and formation of the thiyl radical. In conclusion, our study provides experimental and theoretical evidence that SIN-1 is mainly an one-electron oxidizing agent that can be functionally mimicked by AAPH.
School of Pharmacy, National Defense Medical Center, Taipei, Taiwan ROC.
Shan-Chu
SC
Ho
Shih-Jiuan
SJ
Chiu
Teh-Min
TM
Hu
D000578:Amidines / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D007700:Kinetics; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000737:chemistry; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D000578:Amidines; D005609:Free Radicals; D013438:Sulfhydryl Compounds; C002385:linsidomine; C046728:2,2'-azobis(2-amidinopropane); D008981:Molsidomine