The Chromium, Manganese, and Cobalt Complexes of Transferrin

Abstract

The two metal-binding sites of transferrin will form specific complexes with chromium, manganese, and cobalt ions. Each complex binds bicarbonate in a ratio to the metal ion near unity. In addition to characteristic optical absorption bands in the visible region a specific absorption near 295 mµ is observable for all complexes by difference spectrophotometry. Static magnetic susceptibility measurements indicate that each of the metal ions is bound in the trivalent state, with the cobalt in the low spin diamagnetic form. A distinct difference between the two sites is evident by electron paramagnetic resonance spectroscopy when chromium is bound.