Synergistic anion-directed coordination of ferric and cupric ions to bovine serum transferrin - An inorganic perspective

Musa S. Shongwe, Rachel Smith, Helder M. Marques, Jan A. Van Wyk

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

A series of new iron(III) and copper(II) complexes of bovine serum transferrin (BTf), with carbonate and/or oxalate as the synergistic anion, are presented. The complexes [Fe 2(CO 3) 2BTf], [Fe 2(C 2O 4) 2BTf], [Cu 2(CO 3) 2BTf] and [Cu(C 2O 4)BTf] were prepared by standard titrimetric techniques. The oxalate derivatives were also obtained from the corresponding carbonate complexes by anion-displacement. The site-preference of the transition metal-oxalate synergism has facilitated the preparation and isolation of the mononuclear complex [Cu(C 2O 4)BTf], the mixed-anion complexes [Cu 2(CO 3)(C 2O 4)BTf] and [Fe 2(CO 3)(C 2O 4)BTf] and the mixed-metal complex [FeCu(C 2O 4) 2BTf]. The sensitivity of electron paramagnetic resonance (EPR) spectroscopy to the nature of the synergistic anions at the specific-binding sites of the transferrins has made this physical technique particularly indispensable to this study. None of the other members of the transferrin family of proteins has ever been demonstrated to bind the ferric and cupric ions one after the other, each occupying a separate specific-binding site of the same transferrin molecule, as a response to the coordination restrictions imposed by the oxalate ion. The bathochromic shift of the visible p π-d π* CT band for iron(III)-BTf and the hypsochromic shift of the p π-d σ* CT band for copper(II)-BTf, on replacing carbonate by oxalate as the associated anion, are consistent with the relative positions of these anionic ligands in the spectrochemical series and the nature of the d-type acceptor orbitals involved in the CT transitions. The binding and spectroscopic properties of bovine serum transferrin - a serum transferrin - very nearly mirror those of human serum transferrin, but differ significantly from those of human lactoferrin.

Original languageEnglish
Pages (from-to)199-208
Number of pages10
JournalJournal of Inorganic Biochemistry
Volume98
Issue number2
DOIs
Publication statusPublished - Feb 2004

Keywords

  • Bovine serum transferrin
  • Electronic spectroscopy
  • EPR spectroscopy
  • Metal coordination
  • Synergistic anion

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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