Group-specific ligands

Affinity separations include both group-specific and product-specific classes of interactions. Protein A has been extensively employed as a group-specific ligand to purify monoclonal antibodies, but its specificity is insufficient for some materials. For example, if a monoclonal is harvested in media containing 5% fetal bovine serum, the polyclonal bovine antibodies are not differentiated by a linear gradient on a protein A column but completely separated using step elution on a preparative cation exchanger column (ABx) [147],... 

The use of group-specific ligands for the class separation of nucleosides has found widespread use in the analysis of plasma and urine from patients with various diseases (Dl, D2, G3, G4, K38, P2, U4). 

V. Bouriotis, I.J. Galpin and P.D.G. Dean. Applications of immobilized phenylboronic acids as supports for group-specific ligands in the affinity chromatography of enzymes. J. Chrom. 210 267-278 (1981). 

General, or group-specific, ligands are agents that bind to a family or class of related targets. These ligands are... 

Bioselective adsorption is the process where the affinity is based on biologically relevant binding. It includes group-specific ligands, eg, lectins and nucleotide cofactors (NAD, AMP), and specific ligands, eg, certain less common cofactors (vitamin B12), receptor proteins, and antibodies as used in immunosorbents. 

The low-molecular, group-specific ligands belong to the largest class of ligands used in affinity chromatography ... 

Thiophilic ligands [ 190]. [ 191 ] form a separate class of group-specific ligands that possess high selectivity with respect to immunoglobulins. They are low-molecular compounds, and contain sul-fone and thioether groupings (see below), which show a strong affinity for mono- and polyclonal antibodies in the presence of ammonium sulfate (ca. 1 mol/L). 

Macromolecular group-specific ligands include proteins that are used widely in the purification of biologically relevant macromolecules. Important macromolecular ligands are lectins (for the isolation of glycoproteins), protein A and protein G (for the purification of immunoglobulins), calmodulin (for Ca-dependent enzymes), and the polysaccharide heparin (for the purification of clotting factors and other plasma proteins). 

Table 11.13 Group Specific Ligands Commonly Used in Affinity Chromatography...

The situation is different for some resins with group-specific ligands, where salt, pH or imidazole gradients can be used to obtain high resolution [27]. 

A free hydroxy group is always formed besides the secondary amine group. This increases the hydrophilic property of the resin. The general drawback is that a high pH is required for immobilization. High concentrations and temperature (40 °C) can increase the yield. Some resins with group-specific ligands (such as iminodiacetic acid) are produced by this method. Other popular immobilization methods include ... 

Ramirez-Vick JE, Garcia AA. Recent developments in the use of group specific ligands for affinity bioseparations. Separation and purification methods 1996-97 25(2) 85-129. 

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