title: Magnetic resonance studies of Mn(II)-, Mn(III)-, and Fe(III)-conalbumin complexes.
abstract: Apoconalbumin binds Mn(II) at two sites with association constants of K1 = 7 (+/- 1) X 10(4) and K2 = 0.4 (+/- 0.25) X 10(4) M-1. The binding is tighter in the presence of excess bicarbonate resulting in K1 = 1.8 (+/- 0.2) X 10(5) and K2 = 3 (+/- 2) X 10(4) M-1. The electron paramagnetic resonance spectrum (at both 9 and 35 GHz) of Mn(II) bound at the tight site reveals a rhombic distortion (lambda = E/D approximately equal to 0.25-0.31) in the protein ligand environment of the mental ion. An evaluation of the 1/pT1p, paramagnetic contribution to the longitudinal relaxation rate of solvent protons with Mn(II)-, Mn(III)-, and Fe(III)-derivatives of conalbumin revealed that the mental ion in each site of conalbumin is accessible to one water molecule. For Mn(II)-conalbumin and Mn(III)-conalbumin species, inner coordination sphere protons are rapidly exchanging with the bulk solvent, while slow exchange conditions prevail for Fe(III)-conalbumin.
mesh_terms: D003207:Conalbumin / Q000378:metabolism*; D004527:Egg Proteins / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D007501:Iron / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008345:Manganese / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D004527:Egg Proteins; D003207:Conalbumin; D008345:Manganese; D007501:Iron