Rate acceleration mechanism, origin

Traditionally, the desired monoclonal antibody is selected on the basis of binding affinity to the TSA. This approach led to a multitude of effective catalytic antibodies, the rate acceleration of which, however, is usually orders of magnitude below that of comparable enzymes. Furthermore, detailed mechanistic investigations often revealed a different catalysis mechanism than originally assumed. A different approach for the selection of catalytic antibodies is the reactive immunization where the selection criterion from simple binding is changed to chemical reactivity. 

More work has been done (1-4, 6, on systems with nei -boring sulfenyl sulfur than on any of the other systems listed in Table I. The decompositions of 3 and 4 occur with very similar rates, both showing acceleration of mcve than 10 at 60 We can therefore be reasonably sure ttiat the sulfur of the phenylthio substituent, rather than the phenyl, is responsible for the observed acceleration. The products of decomposition of observed in the original work of Bentrude (1, 2) are adequately explained by the mechanism originally proposed, that of Scheme I. 

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