Hydroxyl groups, haptenation

The conversion of [49] into [50] involves a Claisen rearrangement. Once this was realized it was less surprising that no specific catalytic groups on the enzyme are involved. Support for the Claisen-type mechanism comes from the inhibition shown by the bicyclic dicarboxylate [51], prepared by Bartlett and Johnson (1985) as an analogue of the presumed transition state [52], This same structure [51], coupled through the hydroxyl group to a small protein, was used as a hapten to induce antibodies, one (out of eight) of which mimics the behaviour of chorismate mutase, albeit less efficiently (Table 7). 

A carboxyl group can be introduced in almost any compound by various methods. In cases where a free thiol is present, the carboxyl group can be introduced easily by reaction with bromo- or iodoacetic acid. This reaction is very mild and is usually performed at pH around 8-9. When the hapten contains a hydroxyl group, carboxylic acid may be introduced by one of the following methods (a) carboxymethylation of the hydroxyl group with bromo- or iodoacetic acid (b) esterification with dicarboxylic acid anhydrides, such as succinic anhydride, to yield hemi-succinates, which are unstable above pH 9 (c) reaction with phosgene, which results in the formation of chlorocarbonates. ... 

Synthetic procedures used to prepare antigenic hapten-carrier conjugates are reviewed by Erlanger. Procedures that have proven successful with hapten molecules that possess carboxyl, amino, hydroxyl, and carbonyl groups are fairly routine. The preparation of hapten-carrier conjugates by other synthetic routes is also considered. 

The introduction of I into molecules containing tyrosyl or histidyl moieties can be carried out chemically by the Chloramine T procedure or enzymatically by lactoperoxidase." The prelabeled Bolton-Hunter reagent [A-succinimidyl 3-(4-hydroxyl-5-[ I]iodophenylpropionate] reacts under mild conditions with molecules containing amino groups (e.g., proteins and haptens) to introduce an iodinated propyltyrosyl moi-... 

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