In biochemistry,<unk>  is the technique of<unk> ly reacting a protein or nucleic acid with<unk>  reagents.<unk>  can have several goals, such as
to identify which parts of the molecule are exposed to solvent ("foot printing");
to determine which residues are important for a particular phenotype, e.g., which residues are important for an enzymatic activity;
to introduce new groups into a macromolecule; and
to crosslink macromolecules intra- and intermolecularly.
Chemical modification
Thermal depolymerization
Condensation reaction
Hydrolysis
Polymerization
Carboxylation
Deprotonation
Sterilization 