Transferrin (Tf), an iron transporter, is mainly biosynthesized in the liver, but can also be biosynthesized in the brain; i.e., by oligodendrocytes and the choroid plexus, a cerebrospinal fluid (CSF) producing tissue. The CSF contains two Tf isoforms, brain-type Tf and serum-type Tf, which differ in their glycan structures. Brain-type Tf is uniquely glycolsylated with biantennary asialo- and agalacto-complex type N-glycans that carry bisecting β1,4-GlcNAc and core α1,6-Fuc. The glycans of serum-type Tf in the CSF are similar to those of Tf in serum.

> 95% as determined by Bis-Tris PAGE; > 95% as determined by HPLC