Antibodies chemical reactions

Chemiluminescent Immunoassay. Chemiluminescence is the emission of visible light resulting from a chemical reaction. The majority of such reactions are oxidations, using oxygen or peroxides, and among the first chemicals studied for chemiluminescence were luminol (5-amino-2,3-dihydro-l,4-phthalazinedione [521-31-3]) and its derivatives (see Luminescent materials, chemiluminescence). Luminol or isoluminol can be directly linked to antibodies and used in a system with peroxidase to detect specific antigens. One of the first appHcations of this approach was for the detection of biotin (31). 

FIGURE 14.25 Catalytic antibodies are designed to specifically bind the transition-state intermediate in a chemical reaction, (a) The intramolecnlar hydrolysis of a hydroxy ester to yield as products a S-lactone and the alcohol phenol. Note the cyclic transition state, (b)... 

Wirsching, P, et al., 1995. Reactive immunization. Science 270 1775-1783. Description of reactive immunization, in which a highly reactive compound is used as antigen. Antibodies raised against such an antigen show catalytic activity for tlie chemical reaction that the antigen undergoes. 

Control of chemical activity and selectivity by catalytic antibodies in reactions of heterocycles 95MI11. 

In the last 10 years organic chemists have shown great interest in antibodies that can promote a variety of chemical reactions, even those that are not catalyzed by natural enzymes [84]. 

Hilvert D. Antibody-Catalyzed Concerted Chemical Reactions in Biotechnol Bridging Res. AppL, Proc. U.S.-lsr. Res. Conf. Adv. Appl Biotechnol. 1991 413, Ed. Kamely D., Chakrabarty A. M. and Kornguth S. E., Pb. Kluwer Boston... 

Figure 16.3 Conceptual illustration of two peptides before (left) and after (right) a chemical reaction with formaldehyde. The amino acids are represented as circles. In this particular peptide, a tyrosine (Y) is located within the epitope (shaded circles). An arginine (R) is located elsewhere in the peptide. Formaldehyde results in the formation of a covalent bond between the two residues, due to a Mannich condensation reaction, as shown on the right. The new configuration prevents antibodies from binding to the epitope on the left. 

These data suggest that the loss of immunoreactivity after formalin fixation involves a protein cross-linking reaction. The first amino acid is at or near the antibody epitope. The second can be on the same protein or on another nearby protein. A variety of different chemical reactions with formaldehyde can be occurring. The common theme is that regardless of the details of the formaldehyde-induced cross-linking reaction, steric interference prevents antibodies from gaining access to the epitope. 

A reasonable objection to any in vitro model is whether it accurately mirrors the actual process. A strength of this model is that the peptides in the array, mounted on the microscope glass slide, are the very same as the antibody epitopes in the native proteins. Therefore, the types of formaldehyde-induced chemical reactions at or near the epitope are the same as would likely occur in a tissue sample. An additional strength of the model is that the experimental data using the peptide array completely account for the loss of immunoreactivity after formalin fixation and the recovery of immunoreactivity after antigen retrieval (Fig. 16.5). Nonetheless, our data do not prove that the model accurately represents formaldehyde reactions in tissue specimens. For example, our data do not exclude other causes of steric interference. 

This chapter describes the design, preparation, and use of hapten-carrier conjugates used to elicit an immune response toward a coupled hapten. The chemical reactions discussed for these conjugations are useful for coupling peptides, proteins, carbohydrates, oligonucleotides, and other small organic molecules to various carrier macromolecules. The resultant conjugates are important in antibody production, immune response research, and in the creation of vaccines. 

Janda, K. D. Shevlin, C. G. Lemer, R. A Oxepane Synthesis Along a Disfavored Pathway The Rerouting of a Chemical Reaction Using a Catalytic Antibody J. Am Chem. Soc 1995,117, 2659-2660. 

Antibodies. The reaction between an antibody and its antigen does not result in the chemical modification of the antigen compared with the action of an enzyme and provides the basis for producing chromatographic media capable of selecting the complementary molecules. Either the antigen is insolubilized and used to isolate and purify the appropriate antibodies or with the increased availability of monoclonal antibodies, the reverse procedure is used. 

Since then, catalytic antibodies which catalyze different chemical reactions have been described. The reactions range from ester or carbonate hydrolysis to carbon-carbon bond forming reactions, bimolecular amide formation or peptide bond cleavage, so the application of catalytic antibodies to general synthetic organic chemistry seems to be very promising [22]. 

Once the hapten has been designed and prepared, it is conjugated with a carrier protein to induce the best immunogenicity as possible to elicit an immune response in the animal (most commonly a mouse) in which it is inoculated. The antibodies produced by the defense mechanism of the adaptive immune system that specifically recognizes the hapten are then isolated, overproduced, and purified for testing their catalytic activity toward the targeted chemical reaction. 

Barbas et al offered the following mechanisms shown in Fig. 2 for the Class 1 aldolase reaction and Ab38C2 or Ab 33F12 antibody aldolase reactions, where R is 4-isobutyramidobenzyl or -butyl. Both mechanisms involve a chemically reactive lysyl e-amino group. 

In order to construct functional microspheres by modification of the surface with adsorbed proteins, e.g., enzymes and antibodies, the conformation and orientation of adsorbed proteins must be controlled to keep them as active as free proteins. If hydrophilic particles are used as a carrier, they hardly suffer nonspecific adsorption, but even antibody cannot be adsorbed. In this case, antibody is immobilized on the particles by chemical reactions such as those mentioned in the previous section (9). 

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