Antigen-antibody interaction analysis

Affinity chromatography (12) has become an important tool in the isolation of purified fractions of such substances as enzymes. Advantage is taken of specific interactions such as antigen-antibody interactions. One substance of the pair (e.g. antigen) is bonded to a support. When a mixture is passed through the column, the specific interaction retains the corresponding antibody relative to other substances. A change of mobile phase conditions then elutes the pure antibody. This method has a real potential for analysis of specific proteins in body fluids. 

The coimmunoprecipitation of proteins by an antibody is the standard procedure to demonstrate the presence of interacting proteins. In this method, when a protein is precipitated by a specific antibody, the interacting protein(s) are also precipitated along with the protein precipitated by the antigen-antibody interaction the components of interacting protein are then visualized by Western analysis within the same band on the gel after electrophoresis. 

ELISA (enzyme-Unked immunosorbent assay) is apowerfiil analysis tool for the detection of specific proteins. It has the advantage of running a larger series of samples simultaneously at a high level of sensitivity. The main disadvantage is that protein denaturation, which can occur in processed food, often alters the antigen-antibody interactions. 

The development of antibody-based biosensors presents more difficulties than enzyme-based biosensors as the antigen-antibody interactions are not readily reversible because of the high values of the affinity constants. Another limitation is that the physicochemical changes resulting from the immunochemical reaction are often insufficient to provide detection limits comparable with those of conventional analysis. As a consequence, indirect systems have been developed that rely on the use of enzyme-or fluorescent-tagged reagents. Both competitive and sandwich formats are used. Evanescent wave-induced fluorescence is frequently chosen to avoid possible interferences from the bulk media. For... 

The analysis of peptide structure is central to the enormous advances made in the last 20 years in all aspects of biomedical sciences. The advances in peptide and protein chemistry have been accompanied by the development of a range of analytical procedures that in turn have accelerated the progress made in the imderstanding of, for example, hormone-receptor interactions and antigen-antibody interactions. 

The manipulation of antigen-antibody interactions and subsequent detection of several analytes has been achieved using SIA. Whilst many of these applications have involved the use of SIA with bead injection (to be discussed later), some have used SIA for the direct analysis of cellular and bodily fluids. 

Specific, rapid, and high-affinity recognition of antigens by antibodies is essential for the host s immune system to respond to invasion by foreign cells and pathogens. Pecht and Lancet have presented a cogent analysis of antibody interactions with haptens, and the interested reader will find their examination of the kinetics and thermodynamics to be particularly lucid. Briefly, for the simple one-step binding scheme. 

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