Electrochemical Behavior of the Fe(III) Complexes of the Cyclic Hydroxamate Siderophores Alcaligin and Desferrioxamine E.

Published

Journal Article

The redox behavior of Fe(III) complexes of the cyclic hydroxamate siderophores alcaligin and desferrioxamine E was investigated by cyclic voltammetry. The limiting, pH independent redox potential (E(1/2) vs NHE) is -446 mV for alcaligin above pH 9 and -477 mV for ferrioxamine E above pH 7.5. At lower pH values, the redox potential for both complexes shifts positive, with a loss of voltammetric reversibility which is interpreted to be the consequence of a secondary dissociation of Fe(II) from the reduced form of the complexes. These observations are of biological importance, since they suggest the possibility of a reductive mechanism in microbial cells which utilize these siderophores to acquire Fe. For comparison purposes, cyclic voltammograms were obtained for Fe(III) complexes with trihydroxamic acids of cyclic (ferrioxamine E) and linear (ferrioxamine B) structures, with dihydroxamic acids of cyclic (alcaligin) and linear (rhodotorulic and sebacic acids) structures, and with monohydroxamic acids (acetohydroxamic and N-methylacetohydroxamic acids) at identical conditions. The observed redox potentials allow us to estimate the overall stability constants for fully coordinated Fe(II) complexes as log beta(II)(Fe(2)alcaligin(3)) = 24.6 and log beta(II)(ferrioxamine E) = 12.1. A linear correlation between E(1/2) and pM was found, and the basis for this relationship is discussed in terms of structural (denticity and cyclic/acyclic) and electronic differences among the {alkyl-NOH-CO-alkyl} type of hydroxamic acid ligands studied.

Full Text

Duke Authors

Cited Authors

  • Spasojevic, I; Armstrong, SK; Brickman, TJ; Crumbliss, AL

Published Date

  • February 8, 1999

Published In

Volume / Issue

  • 38 / 3

Start / End Page

  • 449 - 454

PubMed ID

  • 11673947

Pubmed Central ID

  • 11673947

Electronic International Standard Serial Number (EISSN)

  • 1520-510X

Language

  • eng

Conference Location

  • United States