Reactivity of Peroxy Radicals Coordinated to Vitamin B12 Studied by Electron Spin Resonance Spectroscopy

[img]PDF - Authorized users only
Language: English
88Kb
Title:Reactivity of Peroxy Radicals Coordinated to Vitamin B12 Studied by Electron Spin Resonance Spectroscopy
Creators:
Tkáč, Alexander
Hanušovská, Eva
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 69, 11, pp. 2091-2097
Uncontrolled Keywords:Electron transfer, H-transfer reactions, Vitamin B<sub>12</sub>, Antioxidants, Peroxy radicals, Cobalt, ESR spectroscopy, Vitamin E

Abstract

One-electron transfer from chelated Co(II)(3d<sup>7</sup>) of vitamin B<sub>12</sub> (cyanocobalamine) to <i>tert</i>-butylhydroperoxide forms at ambient temperature in non-polar solvents peroxy radicals stabilized by π-coordination to Co(III)(3d<sup>6</sup>) of the oxidized vitamin. In the absence of oxygen, the peroxy radicals manifest themselves as singlet ESR lines at <i>g</i> = 2.0174. After addition of sterically hindered phenols, apart from the decreased original singlet line, a new signal of stable phenoxy radicals, formed by H-abstraction from the phenols, is observed. Phenoxy radicals generated from unhindered phenols remain stabilized by σ-coordination to the cobalt(III) centre, giving rise to an ESR signal split into eight lines due to interaction of the unpaired electron with the magnetic moment of the <sup>59</sup>Co nucleus (<i>I</i> = 7/2) of vitamin B<sub>12</sub>. Large molecules with unhindered OH groups, such as testosterone or cholesterol cannot be coordinated after the primary radical attack and the generated radicals disappear by recombination. By this technique, the sensitivity of biological targets to primary peroxy radical attack as well as the efficiency of different antioxidants (vitamin E, Stobadine) can be tested. <p>

Title:Reactivity of Peroxy Radicals Coordinated to Vitamin B12 Studied by Electron Spin Resonance Spectroscopy
Creators:
Tkáč, Alexander
Hanušovská, Eva
Uncontrolled Keywords:Electron transfer, H-transfer reactions, Vitamin B<sub>12</sub>, Antioxidants, Peroxy radicals, Cobalt, ESR spectroscopy, Vitamin E
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:69
Number:11
Page Range:pp. 2091-2097
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc20042091UNSPECIFIED
ID Code:2323
Item Type:Article
Deposited On:06 Feb 2009 17:17
Last Modified:06 Feb 2009 16:17

Citation

Tkáč, Alexander; Hanušovská, Eva (2004) Reactivity of Peroxy Radicals Coordinated to Vitamin B12 Studied by Electron Spin Resonance Spectroscopy. Collection of Czechoslovak Chemical Communications, 69 (11). pp. 2091-2097. ISSN 0010-0765

Repository Staff Only: item control page