ABSTRACT
Affinity modification was born as a method of the active site-directed irreversible inhibition of enzymes. The hormone ecdysterone stimulates specific genes on polytene chromosomes of Diptera and causes changes in the pattern of specific structural modifications, so-called puffs, present in chromsomes. Characterization of proteases involved in the processing of insulin represents an example of experiments where affinity modification was used to identify enzymatic activity involved in certain biochemical process. The covalent attachment of appropriately labeled affinity reagents to the binding sites allows investigating the localization of these sites in biological systems at various levels of resolution. Further, a similar approach with the label transfer to a competently bound affinity reagent was applied to a number of more stable reactive analogues of initiator nucleotides, including nucleotide 5'-imidazolides. Enzymology is the most advanced field of application of affinity modification.
