Antibody-antigen interactions specificities

There is a continuing demand for fast and simple analytical methods for the determination of many clinical, biochemical and environmental analytes. In this respect, immunoassays and immunosensors that rely on antibody-antigen interactions provide a promising means of analysis owing to their specificity and sensitivity. High specificity... 

Immunoassays employ monoclonal or polyclonal antibody preparations (Chapter 13) to detect and quantify the product (Box 7.1). The specificity of antibody-antigen interaction ensures good assay precision. The use of conjugated radiolabels (RIA) or enzymes (EIA) to allow detection of antigen-antibody binding renders such assays very sensitive. Furthermore, when compared with... 

In fields such as biosensing, analyte binding often relies on very specific molecular recognition interactions that nature has supplied, such as antibody-antigen interactions or strands of complimentary DNA forming double hefices. Unfortunately, because versatile and highly selective receptors for TNT or other explosive molecules are not available, chemists are left to rely on less specific interactions. 

The specificity of antibody-antigen interactions is a result of a structural fit between the antibody binding site and the antigenic determinant. An understanding of the mechanism of the antigen-antibody interactions has revealed the existence of hypervariable and conserved regions. The... 

Proteins and antibodies are natural substrates for affinity columns because of the nature of the enzyme recognition site and the antibody-antigen interaction sites. They have a three-dimensional shape and electrical charge distributions that interact with only specific molecules or types of molecules. Once these substrate sites are identified, molecules can be isolated or synthesized with the key characteristics and used to build affinity supports. These substrates are often bound to a 6-carbon spacer so that they protrude farther away from the packing surface toward the mobile phase and are therefore more available. Certain natural and synthetic dyes have been found to serve as substrate mimics for a class of enzymes call hydrogenases and have been used to build affinity columns for their purification. 

Immunoassay involves the use of the highly specific antibody-antigen interaction for assay of the antigen or the antibody. This method is generally classified into the homogeneous and the heterogeneous formats. 

The concept of receptors is credited to the independent work of Paul Ehrlich (1845-1915) and J. N. Langley (1852-1926). With Ehrlich, the concept appeared to originate from his immunochemical studies on antibody-antigen interactions. Based on the high degree of specificity of antibodies for antigens, Ehrlich postulated the existence of stereospecific, complementary sites on the two molecules. Similar... 

Studies on monoclonal antibodies [94,102,106-110] comprise a significant part of CIEF applications. The affinity of an antibody toward its antigen is highly specific to its conformation, in order to have optimal antibody-antigen interaction. The increase of temperature might cause changes in antibody conformations and this change may be reflected in the isoelectric points (pi values), peak shape, and absorbance of the antibody [109]. 

This chapter deals with the application of immunological techniques to biochemical and molecular biological problems. We discuss the production of polyclonal antibodies and then a range of techniques that depend on the high specificity of antibody-antigen interactions. 

Immunoassays make use of the high specificity of antibody-antigen interactions. Also, coupled reactions are often used to introduce an element of amplification in the detection signal, giving the assays highly desirable properties of specificity and sensitivity. The antibody-antigen interactions can be carried out either in solution or in the solid phase in the latter, the immobilised species can be either the antigen or antibody. 

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