Biospecific ligands

Macromolecules bearing reactive groups in the repeat units along their chains are capable of multiple interaction with the matrix. As early as 1973, Wilchek prepared Sepharose-based supports chemically modified by chemisorbed polylysine and polyvinylamine [41]. The leakage of dyes covalently bonded to these supports was reduced remarkably as compared to non-modified Sepharose activated by cyanogen bromide. Thus, stable and high capacity affinity adsorbents could be prepared by the introduction of macromolecular spacers between a matrix and a biospecific ligand. 

Porous silicas coated with N-VP — AC copolymer may be used as an activated support for the immobilization of the biospecific ligands [50] or for the synthesis of hydrophobic adsorbents [54]. 

Poly (p-nitrophenyl acrylate)-coated wide-pore glass (WPG) was also used as an activated carrier for the immobilization of biospecific ligands and enzymes, A detailed description of properties of these sorbents and catalysts as well as some specific features of their functioning is given in Sect. 6. 

Porous glass (PG) modified with covalently adsorbed poly(p-nitrophenyl acrylate), as described in Sect. 4.1, turned out to be a highly suitable carrier for immobilization of various biospecific ligands and enzymes. When the residual active ester groups of the carrier were blocked by ethanolamine, the immobilized ligands when bound to the solid support via hydrophilic and flexible poly(2-hydroxyethyl acrylamide). The effective biospecific binding provided by the ligands... 

Pseudo-biospecific ligands, such as metal chelates, amino acids, and dyes are simpler and less expensive molecules with a structural affinity to biomolecules (group specificity). Since they have simpler structures, they can be immobilized by stable, well defined chemical reactions to the chromatographic matrix. Their disadvantages are their lower specificity, as compared with biospecific ligands. However, there are many examples of molecules obtained from animal cell cultures that have been successfully purified using pseudo-biospecific ligands (El-Kak and Vijayalakshmi, 1991 Atkins et al., 2005 Serpa et al., 2005 Kumar et al., 2006). 

The resulting affinity sensors can be composed of low-molecular weight biospecific ligands, proteins, enzymes, nucleic adds, and antibodies. Cell membrane components, cell organelles, and intact cells have also been employed. The latter approaches lead to immunosensors and receptrodes. 

The use of small affinity adsorbent particles immobilized in hydrogel beads has been investigated for whole broth processing (1). The adsorbent particles can contain biospecific ligands covalently attached to a porous solid support. A mathematical model was developed to study bioproduct adsorption using immobilized affinity adsorbent beads in batch operation. 

In one of the earliest reports, Schneider et al. [5] followed a similar approach by using a reversibly water-soluble-insoluble copolymer of AT-acryloyl-m-aminobenzamidine, acrylamide and AT-acryloyl-p-aminobenzoic acid where benzamidine was the biospecific ligand, to purify trypsin from beef pancreas by affinity precipitation. 

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