Antibody labeling, or the attachment of a specific tag to an antibody to aid in detection or isolation/purification of a protein, is an important technique.  Labeled antibodies are essential for immuno-based assays such as Western blots, ELISAs, ...

Protein phosphorylation is a common posttranslational modification in which a phosphate moiety is covalently bound to an amino acid.  Phosphorylation occurs through the action of specific protein modifiers called kinases. The reverse reaction, ...

Glycosylation is an extremely diverse, enzymatic process resulting in the covalent attachment of sugars (glycans and monosaccharides) to proteins. About half of all cellular proteins are glycosylated. Most, such as transmembrane receptors, ...