Kinetics of the reaction between ascorbate and free radical from vitamin E as studied by ESR steady-state method
✍ Scribed by V.A. Roginsky; H.B. Stegmann
- Publisher
- Elsevier Science
- Year
- 1993
- Tongue
- English
- Weight
- 721 KB
- Volume
- 65
- Category
- Article
- ISSN
- 0009-3084
No coin nor oath required. For personal study only.
✦ Synopsis
Kinetics of the reaction of phenoxyl radicals (TO ") from a-tocopherol (TOxH) and with aseorbate (AH) (ascorbylpalmitate (AIH)) has been studied in benzene at 37°C by using ESR steady-state method as a model reaction between vitamin E and vitamin C in biological systems. The rate constants for these reactions (kl) were measured by following TO" concentration at continuous free radical generation when AIH was consumed in reaction. For the reaction of AIH with TOI" the value ofk I was found to be 2800 ± 500 M -1 s -1, less by a factor of 102-103 as compared to generally accepted ones reported by Packer et al. (Nature (1979) 278, 737-738) and Scarpa et al. (Biochim. Biophys. Acta. (1984) 801,215-219). A similar value of k I (2500 ± 300 M -I s -I) was obtained for the reaction between AIH and TOIl". The rate constant for self-termination of aseorbyl free radical A x" in benzene at 37°C was found to be (2.3 ± 0.5) x 109 M -I s -I.