TY - JOUR
T1 - Synergistic anion-directed coordination of ferric and cupric ions to bovine serum transferrin - An inorganic perspective
AU - Shongwe, Musa S.
AU - Smith, Rachel
AU - Marques, Helder M.
AU - Van Wyk, Jan A.
N1 - Funding Information:
We are indebted to Professor Eric W. Ainscough (Massey University, New Zealand) for confirmation of the EPR spectroscopic data. DOPSAR (Sultan Qaboos University), the FRD (South Africa) and the Centre for Molecular Design (School of Chemistry, University of the Witwatersrand) are gratefully acknowledged for financial assistance.
PY - 2004/2
Y1 - 2004/2
N2 - 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 [Fe2(CO3)2BTf], [Fe2(C2O4)2BTf], [Cu 2(CO3)2BTf] and [Cu(C2O 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(C2O4)BTf], the mixed-anion complexes [Cu 2(CO3)(C2O4)BTf] and [Fe 2(CO3)(C2O4)BTf] and the mixed-metal complex [FeCu(C2O4)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 pπ-dπ* CT band for iron(III)-BTf and the hypsochromic shift of the pπ-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.
AB - 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 [Fe2(CO3)2BTf], [Fe2(C2O4)2BTf], [Cu 2(CO3)2BTf] and [Cu(C2O 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(C2O4)BTf], the mixed-anion complexes [Cu 2(CO3)(C2O4)BTf] and [Fe 2(CO3)(C2O4)BTf] and the mixed-metal complex [FeCu(C2O4)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 pπ-dπ* CT band for iron(III)-BTf and the hypsochromic shift of the pπ-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.
KW - Bovine serum transferrin
KW - EPR spectroscopy
KW - Electronic spectroscopy
KW - Metal coordination
KW - Synergistic anion
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U2 - 10.1016/j.jinorgbio.2003.10.009
DO - 10.1016/j.jinorgbio.2003.10.009
M3 - Article
C2 - 14729300
AN - SCOPUS:0347091842
SN - 0162-0134
VL - 98
SP - 199
EP - 208
JO - Journal of Inorganic Biochemistry
JF - Journal of Inorganic Biochemistry
IS - 2
ER -