Cross linking, modifying, and labeling proteins are commonly used techniques for studying the structure and interaction of proteins
Cross linking is the process of chemically joining two or more molecules by a covalent bond
Modification involves attaching or cleaving chemical groups to alter the solubility or other properties of the original molecule
Labeling generally refers to any form of cross linking or modification whose purpose is to attach a chemical group (e.g., a fluorescent molecule) to aid in detection