Transferrin, a highly prevalent serum glycoprotein that functions to transport iron to tissues, is present in serum at 3–4 mg/mL and binds iron firmly yet reversibly. Transferrin comprises 679 amino acid residues, is around 80 kDa in size, and possesses two high-affinity Fe3+ -binding sites, one in the N-terminal domain and the other in the C-terminal domain. The half-life of human transferrin is reported to be either 10–12 days or 7–10 days.

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