Pulse radiolysis studies of beta-carotene in oxygenated DMSO solution. Formation of beta-carotene radical cation.
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(.+).
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Ludwig Boltzmann Institute for Radiation Chemistry and Radiation Biology, c/o The University of Vienna, Austria.
D002412:Cations / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004121:Dimethyl Sulfoxide / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry*; D006868:Hydrolysis / Q000528:radiation effects; D007700:Kinetics; D010100:Oxygen / Q000737:chemistry*; D011675:Pulse Radiolysis; D012996:Solutions / Q000737:chemistry; D013053:Spectrophotometry; D019207:beta Carotene / Q000737:chemistry* / Q000528:radiation effects
D002412:Cations; D005609:Free Radicals; D012996:Solutions; D019207:beta Carotene; D010100:Oxygen; D004121:Dimethyl Sulfoxide