Antigen-antibody affinity interactions

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. 

Antibody avidity is commonly applied to antigen-antibody interaction, where multiple, weak, noncovalent bonds form between antigen and antibody. Avidity is distinct from affinity, which is a term used to describe the strength of a single bond. As such, avidity is the combined synergistic strength of bond affinities rather than the sum of bonds. 

The examples mentioned up to now utilized strong Ag-Ab interactions using the equilibrium-mixture mode of ACE. But the quantitation of weak antigen-antibody interaction is also possible by ACE, if the mobility-shift approach, sometimes also called dynamic equilibrium affinity electrophoresis, is applied. 

The interaction between biological macromolecules can be of various degrees of complexity. These interactions may be of high specificity, as in antigen-antibody complexes, or of low specificity, as in protein-lipid associations. The complexes that are formed may be very stable, or highly unstable. These properties of a complex must be considered in selecting an affinity adsorbent to be used for the purification of a specific substance. 

Photoswitchable sub strate-protein / cofactor- enzyme/antigen-antibody interactions Light-stimulated affinity chromatography Immobilization of photoactive separation component on solid matrices... 

In addition, affinity CE separation was carried out to resolve monoclonal anti-BSA and BSA in dilute mouse ascites fluid. Then the affinity constant of this antigen-antibody interaction was measured [1004]. 

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