Antigen construction, determination

Antibodies, advantages for sensor use, 311 Antigen construction, determination, 312,314,315/... 

Figure 22.17 Antibody-liposome conjugates may be used as targeting reagents for detection or therapeutic applications. The liposome may be constructed to contain fluorescent molecules for detection purposes or bioactive agents for therapy. The antibody component targets the complex for binding to specific antigenic determinants.

Once a standard curve has been constructed, the RIA can determine the concentration of hormone in a sample (usually plasma or urine). The values of hormone levels are usually accurate using the RIA, but certain factors (e.g., pH or ionic strength) can affect antigen binding to the antibody. Thus similar conditions must be used for the standard and the sample. 

Non-labelled immunosensors rely on various principles (Fig. 3.27.A). Either the antibody or the antigen is immobilized on the solid matrix to form a sensing device. The solid matrix should be sensitive enough at the surface to detect immunocomplex formation. Electrode, membrane, piezoelectric and optically active surfaces may in principle be used to construct non-labelled immunosensors. The antigen or antibody to be determined is dissolved in a solution and reacted with the complementary matrix-bound antibody or antigen to form an immunocomplex that alters the physical e.g. the electrode potential or intrinsic piezofrequency) or optical properties of the... 

Kragol, G., Otvos, L Jr., Feng, J., Gerhard, W and Wade, J.D. (2001) Synthesis of a disulfide-linked octameric peptide construct carrying three different antigenic determinants. Bioorg. Med. Chem. Lett. 11,1417-1420. 

Various strategies have been used to combine the variable region of antibodies, which bind to the antigen determinants, with small functional proteins. Such constructs can be produced on a large scale in various expression systems (Irving et al., 1996 Roque et al., 2004) bacterial expression systems are relatively simple and less expensive than the alternatives, but eukaryote expression systems (yeast, mammalian, and insect cells) are also being used for this purpose (Roque et al., 2004). 

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