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Title: Pulse radiolysis studies of the reaction of nitrogen dioxide with the vitamin B₁₂ complexes Cob(II)alamin and nitrocobalamin

Although now recognized to be an important reactive nitrogen species in biological systems that modifies the structures of proteins, DNA and lipids, there few studies on the reactivity of ˙NO2, including the reactions between ˙NO2 and transition metal complexes. We report kinetic studies on the reaction of ˙NO2 with two forms of vitamin B12 – cob(II)alamin and nitrocobalamin. UV-vis spectroscopy and HPLC analysis of the product solution show that ˙NO2 cleanly oxidizes the metal center of cob(II)alamin to form nitrocobalamin, with a second-order rate constant of (3.5 ± 0.3) × 10⁸ M⁻¹ s ⁻¹ (pH 7.0 and 9.0, RT, I = 0.20 M). The stoichiometry of the reaction is 1:1. No reaction is detected by UV-vis spectroscopy and by HPLC analysis of the product solution when nitrocobalamin is exposed to up to 2.0 mol equiv.˙NO2.
Authors:
 [1] ;  [2] ;  [3]
  1. Kent State Univ., Kent, OH (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Auckland Univ. of Technology, Auckland (New Zealand)
Publication Date:
OSTI Identifier:
1182504
Report Number(s):
BNL--107426-2015-JA
Journal ID: ISSN 0162-0134; R&D Project: CO-004; KC0304030
Grant/Contract Number:
SC00112704
Type:
Accepted Manuscript
Journal Name:
Journal of Inorganic Biochemistry
Additional Journal Information:
Journal Volume: 142; Journal ID: ISSN 0162-0134
Publisher:
Elsevier
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY laser electron accelerator facility