Multiple affinity removal system

The Agilent multiple affinity removal system utilizes the specificity of antibody-antigen recognition for 14 highly abundant proteins from human serum samples. The affinity column achieves reproducible and specific depletion from human serum and plasma to eliminate 94% of interfering proteins. It allows identification of proteins down to nanograms per milliliter level as reported by Agilent. 

Depletion of these and several other abundant proteins allow for in-depth analysis of low-abundance ones. There are many commercial products for protein immunodepletion. Applications of the products are reported for a Seppro column in a label-free method (135), Seppro column in a SILAP method (136), a Hu-6 Multiple Affinity Removal System (MARS) kit in an iTRAQ method (137), and a Hu-6 MARS kit in another iTRAQ -based method (138). Caution should be observed if a low-abundance protein has affinity to a high-abundance protein because it can be co-depleted. 

More specific and complete depletion of targeted abundant proteins to enable detection of low abundant proteins have been demonstrated with individual antibody methods. For instance, an immunodepletion strategy based on use of polyclonal antibodies such as the commercially available multiple affinity removal system (MARS) has shown rapid and efficient depletion of serum proteins. The system depletes the six most abundant proteins in human plasma (i.e., albumin, IgG, IgA, transferrin, haptoglobin, and antitrypsin). These six most abundant proteins represent approximately 85% of the total protein mass in human serum or plasma (Echan et al., 2005). Tissue plasminogen activator (tPA), 10—60 ng/mL in human plasma, was detected by 2D gel followed by MARS depletion of the six most abundant proteins (Cho et al., 2005). With the use of the more sensitive LC—MS/MS platform, a detection limit of tPA down to low nanogram/milliliter concentration range should be practical. 

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