Bioaffinity

N. Guzman, On-line bioaffinity, molecular recognition and preconcenti ation in CE technology , EC-GC, 17 16 (1999). 

The described bioaffinity separations demonstrate that polyacrylamide spacers aid the selective binding of highly complex and delicate biomacromolecules and their associates. Moreover, these solutes remain biologically active after desorption probably due to the high inertness and flexibility of the surrounding polymer chains fixed on the solid support. The unbound parts of serum usually show no loss of the activities of their constituents. Thus we evaluate the surface of inorganic supports coated with chemisorbed iV-hydroxyethyl polyacrylamide and its derivatives as being biocompatible. 

Reviews of w/o-ME-based LLE of biomolecules are readily available [4,57,102-104]. However, new results have been generated in this field since the publication of the cited reviews. For instance, there has been a large amount of research involving new surfactant and surfactant systems, particularly those involving nonionic and natural surfactants such as phosphatidylcholine and bioaffinity surfactants (Table 1), in order to increase biocompatibility and selectivity and prevent denaturation that occurs using ionic surfactants. The more recent results along these lines will be presented here, along with an overview of the LLM process. 

In addition to the covalent binding, some methods derived from bioaffinity chromatography can be used for non covalent attachment of antibodies to a surface by the inactive Fc portion. The advantage is that antigen binding sites stay undamaged and accessible for the analytes due to the orientation of antibody with the active Fab portions towards the tested medium. 

Biosensors may be classified into two categories biocatalytic biosensors and bioaffinity biosensors. Biocatalytic sensors contain a biocatalyst such as an enzyme to recognize the analytic selectively. Bioaflinity biosensors, on the other hand, may involve antibody, binding protein or receptor protein, which form stable complexes with the corresponding ligand. An immunosensor in which antibody is used as the receptor may represent a bioaflinity biosensor. 

The bioaffinity parameter a basically reflects the free metal ion concentration, whereas the limiting flux ratio b reflects the total labile metal species concentration. Due to the complexation, the ratio a/b thus changes by a factor (1 +sKcl) in spherical geometry, while the factor (1 I sKc ) (l I Kc ) is required for planar geometry [26]. 

Bioaffinity chromatography, 6 399—400 Bioantimutagen, vanillin as, 25 556 Bioassay dyes, 9 518 Bioassays, microfluidics in, 26 968-969 Bioaugmentation, defined, 3 758t Bioaugmentation/bioremediation effluent treatment, 9 436, 438 Bioavailability, of antisense oligonucleotides, 17 628 Biocatalysis, 3 668-683 16 395. See also Biocatalyst entries... 

PORATH, J. J. Chrom. 218 (1981) 241. Development of modem bioaffinity chromatography. 

R. J. Derks, A. C. Hogenboom, G. van der Zwan, H. Irth On-line continuous-flow, multi-protein biochemical assays for the characterization of bioaffinity compounds using electrospray quadmpole time-of-flight mass spectrometry. Anal Chem 2003, 75, 3376-3384. 

These preliminary developments have relied on either metabolic enzyme reactions (viz. those where the substrate is consumed and a product is formed as a result) and bioaffinity reactions (viz. those that are followed via electron density changes). This Section discusses sensors based on immobilized enzymes and both types of reaction metabolic and bioaffinity. 

Table 13.1 lists a number of ligands that are used in bioaffinity applications. These, and many other biological compounds, can be attached to chromatographic supports using the materials and methods described previously in this chapter. Many commercial suppliers even provide these ligands already coupled to supports or packed in columns. Several hundred different types of immobilized biological molecules are presently available in this fashion [3-6,21,25]. 

The earliest applications of bioaffinity chromatography involved its use in enzyme purification (see Figure 13.7) [7]. Enzyme purification has continued to be a major application of this technique [57]. Some ligands that are employed for this purpose are enzyme inhibitors, coenzymes, substrates, and cofactors. Examples include methods that use nucleotide mono-, di-, and triphosphates for the... 

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