Pulse radiolysis studies of beta-carotene in oxygenated DMSO solution. Formation of beta-carotene radical cation

Radiation Research
N Getoff

Abstract

The spectroscopic and kinetic characteristics of beta-carotene radical cation (beta-carotene(.+)) were studied by pulse radiolysis in aerated DMSO solution. The buildup of beta-carotene(.+) with k(1) = (4.8 +/- 0.2) x 10(8) dm(3) mol(-1) s(-1) [lambda(max) = 942 nm, epsilon = (1.6 +/- 0.1) x 10(4) dm(3) mol(-1) cm(-1)] results from an electron transfer from beta-carotene to DMSO(.+). The beta-carotene(.+) species decays exclusively by first-order reaction, k = (2.1 +/- 0.1) x 10(3) s(-1), probably by two processes: (1) at low substrate concentration by hydrolysis and (2) at high concentrations also by formation of dimer radical cation (beta-carotene)(2)(.+). Under the experimental conditions, a small additional beta-carotene triplet-state absorption ((3)beta-carotene) in the range of 525 to 660 nm was observed. This triplet absorption is quenched by oxygen (k = 7 x 10(4) s(-1)), resulting in singlet oxygen ((1)O(2)), whose reactions can also lead to additional formation of beta-carotene(.+).

References

Feb 1, 1972·Photochemistry and Photobiology·P Mathis, A Vermeglio
Apr 14, 1994·The New England Journal of Medicine·Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group
Nov 6, 1996·Journal of the National Cancer Institute·S T MayneG Beecher

Citations

Jul 25, 2006·Biochimica Et Biophysica Acta·Joseph L HughesElmars Krausz
May 23, 2003·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·K Razi NaqviVassilia Partali

Related Concepts

Cations
High Pressure Liquid Chromatography Procedure
Rheumabene
Free Radicals
Hydrolysis
Dioxygen
Pulse Radiolysis
Solutions
Spectrophotometry
Carotaben

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