Haptens, design

While the presentation thus far has emphasized the programmed relationship of hapten design and consequent antibody catalytic activity, there is a growing number of examples where the detailed examination of catalysis reveals mechanistic features that were not evidently design features of the system at the outset. Such discoveries are clearly a strength rather than a weakness of... 

From the results reported to date, it seems that the manner in which haptens are attached to carrier proteins leads to significant differences in certain cases. Clearly, haptens designed with aromatic moieties between the linkage to the immunogenic carrier protein and the TSA motif often have better antibody recognition. Recently, Hilvert pointed out that on both micro and macro levels, mechanistic improvements arise as a function of time. The differences in time scales for the evolution of natural enzymes and antibodies — millions of years versus weeks or months — also appear to be an explanation of the low efficiency of antibody catalysts. He also highlighted that the unique immunoglobulin fold has not been adopted by nature as one of the common scaffolds on which to build enzyme catalytic machinery. Therefore, antibody structure itself places limitations on the kind of reactions amenable to catalysis. 

Hapten design strategy for generation of an active site with a suitable catalytic residue has been further demonstrated. Thus, catalytic antibody 43D4-3D12, which was generated against the tertiary amine (61), has been found to catalyse the selective... 

Lee, N., D.P. McAdam, and J.H. Skerritt. 1998. Development of immunoassays for type II synthetic pyrethroids. 1. Hapten design and application to heterologous and homologous assays. J. Agric. Food Chem. 46 520-534. 

Naturally occurring redox enzymes have been successfully exploited for asymmetric synthesis for some years.1 Although impressive chemo-, regio-, and enantioselectivities have been achieved in some cases, these biocatalysts have prescribed selectivity and often require expensive cofactors that must be recycled for preparative work. Catalytic antibodies offer an attractive alternative, since they are not limited a priori by Nature s choices. Thus the need for cofactor recycling can be circumvented through the use of inexpensive oxidants and reductants, and, as we have seen above, selectivity can be tailored through appropriate hapten design. 

C. 84G3 Combining TSA and Reactive Immunization 1. Hapten Design... 

In our original hapten design for aldolase antibodies, the /3-diketone functionality of hapten 4 was used as a reactive immunogen to trap a chemically reactive lysine residue in the active site of an antibody as a stable enaminone. The chemical mechanism leading up to the stabilized enaminone should match that of Class I aldolases over this portion of the reaction coordinate. 

Success in the synthesis of new catalytic antibodies (CAs) depends on the efficiency of each of the following steps 1) hapten design, 2) immunogen synthesis, 3) preparation of the enzymatic tracer 4) generation and purification of antibodies and 5) kinetic assays. 

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