Online single-step analysis of blood proteins: The transferrin story

The serum iron transport protein human transferrin (hTf) is a glycoprotein (MW similar to 79.6 kDa) containing two Asn-linked sites of glycosylation. The presence of specific glycoforms of hTf has been used as an indicator of carbohydrate-deficient glycoprotein syndrome (CDGS) or an indicator of alcohol abuse. The exact nature of the glycoforms described in the literature is controversial. In this work we demonstrate that the altered hTf glycoforms have lost one or both complete glycan side chains. Furthermore, we demonstrate using a combination of online immunoaffinity-postconcentration-mass spectrometry in conjunction with a blood spot cartridge that we can determine the relative quantities of the hTf glycoforms using <5 muL blood in under 30 min. This is in contrast to previous methods that used 1 m-L and took 4 days. We show that this method can be useful to analyze hTf from CDGS and alcoholic patients. (C) 2001 Academic Press.