Antibody-binding epitope

Figure 7.2 Schematic showing the relationship of the native antigen to the peptide mimic. The native antigen (a protein) is shown as a winding, twisted line, so as to represent a hypothetical three-dimensional structure. The peptide represents the antibody-binding epitope (shown in dotted lines) of the native antigen. The epitope can represent a linear sequence of the native protein. Alternatively, the epitope can be formed by amino acids that are not immediately adjacent to each other in the primary sequence but brought together by the three-dimensional folding of the protein. Adapted with permission from Sompuram et al.6...

Liu et al. [140] have also used this interface for an electrochemical immunosensor for small molecules (Figure 1.26). In this sensor, one end of the molecular wire is attached to ferrocene dimethylamine with a covalent link formed between one of the amine group son the ferrocene and the carboxyl group on the wire. To the other amine is attached the antibody-binding epitope for the antibody, in this proof-of-concept study the epitope is biotin. Electron transfer can be readily achieved to the ferrocene molecule but upon antibody binding to this interface, the electrochemical signal is dramatically reduced. 

Lightowlers, M.W., Waterkeyn, J.G., Rothel, J.S., Gauci, C.G. and Harrison, G.B. (1996c) Host-protective fragments and antibody binding epitopes of the Taenia ovis 45W recombinant antigen. Parasite Immunology 18, 507-513. 

Mn-SOD was purified from human liver according to the method described previously (12). A typical purification procedure for human liver Mn-SOD is shown in Table 3 (M13). A monoclonal antibody, PG 11, was raised in mice against the human liver Mn-SOD. The competition experiments using synthetic peptides revealed that the antibody-binding epitope was localized in the COOH-terminal peptides as described previously (K4). 

Residual tumor cells can proliferate following therapeutic MAb treatment and those lacking the target antigen, or even just the antibody-binding epitope. 

Epitope inaccessible to antibody binding after formalin fixation. 

Antisen, any substance that stimulates the immune system. Antigens are often foreign substances such as bacteria or viruses that invade the body. An antigen is a ligand that contains a region or epitope which is specifically recognized by an antibody binding site. 

Fig. 1. Diagram of an EM immunogold assay localizing a protein on plastic sections. The primary antibody binds to an exposed surface epitope of the embedded cells. The antibody is then visualized by binding a second antibody coupled to a colloidal gold particle. The electron-dense gold particle visibly marks the position of the bound antibodies when visualized with the electron microscope. 

Antibody affinity from the Latin, affinis = connected with, having things in common. In immunohistochemistry, antibody affinity determines the strength of binding of a monovalent antibody, such as Fab fragment, to one epitope, i.e., how tightly an antibody binds to its particular antigen. 

Epitope is an antigenic determinant (a part of a molecule to which an antibody binds), which is a biological structure or sequence, such as a protein or carbohydrate, that is recognized by the immune system and to which an antibody binds. 

Epitope The region of an antigen to which antibody binds specifically. This is also known as the antigenic determinant. 

As a consequence, any nonspecific adsorption of protein to the interface will also cause an attenuation in electrochemistry. Hence, the antifouling layer is required to ensure the attenuation of the electrochemistry associated with the presence of antibodies is due to a specific interaction with the binding epitope on the molecular wire rather than any nonspecific effects. The ability of this layer to resist nonspecific adsorption of proteins, as well as preventing electroactive species reaching the electrode, was demonstrated by Liu and Gooding [131] previously and is demonstrated in the current paper via controls that show there is little attenuation in the ferrocene electrochemistry if a different antibody is used or if the biotin epitope is absent from the interface. 

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