The Comparative Study of Binding Characteristics of Cobalt and Iron to Human Serum Transferrin

Abstract

Background: Cobalt (Co) is an essential trace element. Available data suggest an interaction between cobalt and other ele- ments. In this study the characteristics of Co and iron (Fe) bindings to human apo-transferrin (apo-tf) have been investigated and compared. Methods: Using spectrophotometric titration and equilibrium dialysis techniques, the bindings of Co(III) and Fe(III) to apo-tf were studied. Results: Both Fe (III) and Co (III) as complexes with citric acid (1:20) were taken up by apo-tf, forming complexes with the maximum absorbances at 465 nm and 360 nm respectively. Conclusion: The binding of iron to apo-tf at 465 nm was reduced by 20% when 225 nmole/ml of cobalt was added to the reaction mixture. The binding constant of iron to apo-tf was calculated using scatchard plot analysis and it was 22×109 M- 1.The addition of cobalt (III), 200 µg/l to the outside of the dialysis sac reduced iron Uptake by 30%. The binding constant of Co (III) to apo-tf was also calculated and it was 3×109 M-1.
Keywords: cobalt-transferrin, iron-transferrin, binding activity