ABSTRACT
Only few of the reactions known to organic chemists can be used in affinity modification. The great majority of affinity reagents are represented by electrophiles since reactive side-chain groups as well as some groups of the main chains of biopolymers are nucleophilic. Amides and esters of haloacids were the first reactive groups used in affinity reagents. Nucleotide coenzymes NAD and NADP participate in the hundreds of oxidation-reduction transformations of hydroxy and carboxylic groups as well as the aldehyde and carboxylic groups. Diazoketones and diazoacetates which are used mainly as UV-light activatable precursors of carbines can serve as alkylating groups in the dark. Acylating groups readily react with amino groups of proteins. Some cations play central roles in enzymatic catalysis being enzyme cofactors such as zinc in carboxypeptidase or part of enzyme prosthetic groups such as iron in hemoglobin. This branch of bioorganic chemistry is considered as a separate field of science, bioinorganic chemistry.
