Document Detail

Kinetics and mechanism of the reduction of CrVI and CrV by D-lactobionic acid.
MedLine Citation:
PMID:  14729315     Owner:  NLM     Status:  MEDLINE    
The oxidation of D-lactobionic acid by Cr(VI) yields the 2-ketoaldobionic acid and Cr(3+) as final products when a 20-times or higher excess of the aldobionic acid over Cr(VI) is used. The redox reaction takes place through a complex multistep mechanism, which involves the formation of intermediate Cr(IV) and Cr(V) species. Cr(IV) reacts with lactobionic acid much faster than Cr(V) and Cr(VI) do, and cannot be directly detected. However, the formation of CrO(2)(2+), observed by the first time for an acid saccharide/Cr(VI) system, provides indirect evidence for the intermediacy of Cr(IV) in the reaction path. Cr(VI) and the intermediate Cr(V) react with lactobionic acid at comparable rates, being the complete rate laws for the Cr(VI) and Cr(V) consumption expressed by: -d[Cr(VI)]/dt=[k(I)+k(II)[H(+)]][lactobionicacid][Cr(VI)], where k(I)=(4.1+/-0.1) x 10(-3) M(-1) s(-1) and k(II)=(2.1+/-0.1) x 10(-2) M(-2) s(-1); and -d[Cr(V)]/dt=[k(III)[H(+)]+(k(IV)+k(V)[H(+)])[lactobionicacid]] [Cr(V)], where k(III)=(1.8+/-0.1) x 10(-3) M(-1) s(-1), k(IV)=(1.1+/-0.1) x 10(-2) M(-1) s(-1) and k(V)=(1.0+/-0.1) x 10(-2) M(-2) s(-1), at 33 degrees C. The Electron Paramagnetic Resonance (EPR) spectra show that five-co-ordinate oxo-Cr(V) bischelates are formed at pH 1-5 with the aldobionic acid bound to Cr(V) through the alpha-hydroxyacid group.
Viviana Roldán; Mabel Santoro; Juan C González; Juan Manuel Salas-Peregrin; Sandra Signorella; Luis F Sala
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of inorganic biochemistry     Volume:  98     ISSN:  0162-0134     ISO Abbreviation:  J. Inorg. Biochem.     Publication Date:  2004 Feb 
Date Detail:
Created Date:  2004-01-19     Completed Date:  2004-09-23     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7905788     Medline TA:  J Inorg Biochem     Country:  United States    
Other Details:
Languages:  eng     Pagination:  347-57     Citation Subset:  IM    
Departamento de Ciencias Básicas, Facultad de Ciencias Veterinarias, UNL, R.P. Kreder 735, Esperanza, Argentina.
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MeSH Terms
Carcinogens, Environmental / chemistry*,  metabolism
Chromium / chemistry*,  metabolism
Disaccharides / chemistry*,  metabolism
Spectrophotometry, Ultraviolet
Time Factors
Reg. No./Substance:
0/Carcinogens, Environmental; 0/Disaccharides; 18540-29-9/chromium hexavalent ion; 7440-47-3/Chromium; 96-82-2/lactobionic acid

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