Antibody selective binding

The chemical interest of these trace amount proteins stems from the fact that they can be used as catalysts or enzyme analogs for almost any chemical reaction (Tramontano et al., 1986 Pollack et al., 1986 Lemer et al., 1991). The fundamental difference between antibodies and enzymes does not relate so much to the protein structures as to the structure and lifetime of the substrates. Antibodies selectively bind molecules in their ground state, whereas enzymes selectively produce and then bind more strongly to short-lived transition states. Antibody-antigen complexes tend toward precipitation, whereas enzyme-transition state complexes react to enzyme-product complexes, which immediately dissociate. In both cases, however, the same noncovalent bonds are used. 

The water-soluble carbonyl 16.29 has been used as a stable label for biomolecules where it is found to bind to histidine-repeat (His-His-His-) regions. An antibody has been labeled with the "Tc complex so that the y-ray image obtained as a result of the y-emission of this Tc isotope shows the location of a tumor to which the antibody selectively binds. Technetium imaging with various coordination complexes has become a standard procedure in medicine. ... 

Wallraff, E., Schleicher, M., Modersitzki. M Reiger, D., Isenberg, G., Gerish, G. (1986). Selection of Dictyostelium mutants defective in cytoskeletal protein Use of an antibody that binds to the ends of alpha-actinin rods. EMBO J. 5,61-67. 

The concept of immunoassay was first described in 1945 when Landsteiner suggested that antibodies could bind selectively to small molecules (haptens) when they were conjugated to a larger carrier molecule. This hapten-specific concept was explored by Yalow and Berson in the late 1950s, and resulted in an immunoassay that was applied to insulin monitoring in humans. This pioneering work set the stage for the rapid advancement of immunochemical methods for clinical use. 

TES-45 and TES-55 are two glycoproteins that have yet to be identified at a genetic level, but evidence has been obtained that they may also be lectins. Carbohydrate affinity chromatography with mannose-agarose shows that TES-32 selectively binds as expected, but that TES-45 is also present in small amounts (Loukas et al., 1999) unlike TES-32, TES-45 does not bind to A -ace Lylgalac t< isamine. No sequence information has yet been obtained on TES-45, but it is recognized by polyclonal antibodies generated to TES-32,... 

Clear identification of tumour-associated antigens would facilitate the production of monoclonal antibodies capable of selectively binding to tumour tissue. Such antibodies could be employed to detect and/or destroy the tumour cells. 

Antibodies against sugars (carbohydrate residues) can be difficult to obtain and lectins are a solution to these problems. Lectins are naturally occurring plant and animal proteins or glycoproteins that selectively bind noncovalently to carbohydrate residues. Lectins can be labeled directly or secondary antibodies against lectins enables the use of other immuno techniques (30) including electron microscopy (31). 

The most interesting developments involve catalysis of simple aldol reactions. The key to reactive immunisation is the use of a hapten that is chemically reactive, rather than a passive template. This means that (i) relevant chemistry is going on during the course of antibody induction, which thus happens in the presence of intermediates involved in the reaction, and so may be modified to favor the formation of antibodies which bind these intermediates (and perhaps transition states leading to them). Furthermore (ii) it becomes possible to select for antibodies that react with, rather than just bind, to the hapten. The system used for the development of aldolase antibodies is outlined in Scheme 2... 

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