Boron of the type described, or otherwise composed, may also be incorporated into antibodies using derivatizing agents that already contain boron in the form of boronic acid or its esters and further containing a derivatizing group Y. The general formula for suitable derivatizing agents is: ##STR1## where R1 and R2 can be either an alkyl group such as ethyl, propyl, butyl, etc., hydrogen or an ary