Effective depletion of albumin using a new peptide-based affinity medium

Blood plasma and serum are very useful samples for the detection, identification and quantitation of proteins associated with both health and disease. However, analysis of plasma and serum is a challenge because traces of interesting polypeptides and proteins can be dominated by the very high concentration of albumin present. Albumin may be depleted by adsorption to immunoaffinity columns or to columns containing dyes such as Cibacron Blue, or by ultrafiltration, but these methods are far from ideal. We describe a new peptide-based affinity medium which is effective for removing albumin and is very specific. The albumin-binding capacity is at least 14 mg per mL of gel. The material may be reused hundreds of times after a simple regeneration step involving NaOH, with full retention of specificity and capacity. The material was tested with human and monkey plasma and serum and rat serum, and has been used to deplete litre volumes of human plasma. The development of other peptide-based affinity media to deplete abundant proteins is briefly discussed.