Primary or secondary amino groups are ubiquitous in biomolecules. They are present in proteins and peptides as ε-amino groups of lysines and N-terminal amino groups. Many natural and synthetic small molecules are amines, and DNAs with amino groups can be prepared by solid phase synthesis and enzymatically.

Tetrafluorophenyl (TFP) esters belong to a group of activated esters widely used to conjugate fluorophores to the primary and secondary amines of biomolecules. Like hydroxysuccinimide (NHS) esters, they form a strong amide bond between the dye and the compound being modified; however, TFP esters are more stable at the basic pH values typically associated with reactions with amines and are also less susceptible to spontaneous hydrolysis.