Phenyl azides are a well-known class of photoaffinity probes that require photoactivation at short wavelengths (∼260 nm). Unfortunately, 260 nm UV causes damage to proteins, nucleic acids and other biological samples. This fluorinated phenyl azide can be effectively photoactivated at ∼300 nm, thus minimizing the photodamages caused by the short UV light. 4-Azido-2,3,5,6-tetrafluorobenzoic acid succinimidyl ester is an excellent building block to introduce photoaffinity function into proteins and other amino-containing biomolecules such as peptides and amino-modified oligos. Phenyl azides are known for their ability to undergo photochemical reactions when exposed to ultraviolet (UV) light, specifically by forming highly reactive carbene intermediates that react with nearby molecules, forming covalent bonds. The singlet nitrene intermediate formed on photoactivation is highly reactive. This property makes phenyl azides useful for studying protein-protein, protein-nucleic acid interactions, ligand-receptor binding, and other biomolecular interactions.