Used as a spin label in electron paramagnetic resonance (EPR) spectroscopy to study protein dynamics and conformational changes. It is typically attached to proteins via covalent amide bonds to carboxyl groups, such as at the C-terminus or on aspartic/glutamic acid side chains. Its primary application lies in probing molecular environments in biological systems, especially for monitoring local structural changes and mobility in peptides and proteins. Due to its stability and sensitivity to environmental polarity and viscosity, it serves as a valuable tool in biophysical research for investigating membrane proteins, protein folding, and intermolecular interactions. Additionally, it finds applications in targeted drug delivery systems and laboratory-level medical imaging, particularly for developing indicators of inflammation or oxidative stress in tissues. It is also employed in polymer science to examine chain motion and microstructure in synthetic macromolecules.