Stereospecific immuno-recognition of the tetracyclic anti-depressant oxaprotiline

Stereoselectivity of antibodies for the bioanalysis of chiral drugs

The use of immunoassay techniques represents an alternative approach to the more common chromatographic methods for the determination of the concentrations of chiral drugs. In the development of the former technique, the inherent stereoselectivity of the antibodies used appears to be an important parameter to be studied. The structural features of the drug, including the environment around the asymmetric center, the flexibility of the molecule and the ability of the molecule to undergo racemization, contribute to the molecule's ability to be recognized by stereoselective antibodies. These parameters are intrinsic and can not be influenced by the investigator. On the other hand, other parameters can be modified to favor the raising of highly stereoselective antibodies. These include the synthesis of an appropriate hapten; the selection of an optimal spacer arm between the hapten and the carrier protein used for the immunization procedure; and the choice of appropriate immunization and antibody-screening procedures. The purification of antibodies using affinity chromatography may also facilitate the selection of stereoselective antibodies.

Association constants of monoclonal antibodies for hapten: heterogeneity of frequency distribution and possible relationship with hapten molecular weight

Using published data, we have investigated the relationship of the association constant (Ka) of 265 MAbs for haptens with molecular weights ranging from 111 to 1202 Da. The study indicates that: (1) differences of a factor 10(3)-10(5) are frequently found between the lowest and the highest value of Ka for the same hapten; (2) the relationship between log Ka and the hapten molecular weight of either the native drug or the molecular entity used for the Ka determination is described by a hyperbolic function; (3) beyond a critical molecular weight of approximately 300-325 Da, the log Ka reaches a plateau at a maximal value near 10(-12) M-1.