Patent ID: 6870065

Claim:
A reagent having the general formula of General Formula I: wherein group R is an electrophilic or a nucleophilic moiety suitable for reaction of the reagent with a biologically active species; wherein group R 2 is selected from one of H and OH moieties; wherein group R 3 is selected from one of an alkyl and a methylene bearing an electronegative substituent; wherein group Z is a spacer selected from one of (CH 2 ) n and CH 2 O(CH 2 CH 2 O) n 2 , and n is an integer of from 1 to 5, and n 2 is an integer of from 1 to 4; and wherein each of group Z 2 and Z 3 comprise (CH 2 )CONH(CH 2 ) 3 CONH(CH 2 ) 2 .