Dansyl cadaverine is an amine-containing Dansyl building block. Dansyl cadaverine is also the most popular fluorescent transglutaminase substrate to label proteins by transaminidation. It has also been used to prepare other small fluorescent biomolecules via amidation or reductive amination. It should be noted that the Dansyl fluorescence is highly environment-sensitive. Dansyl dyes have environmentally sensitive fluorescence quantum yields and emission maxima along with large Stokes shifts. This environment-sensitive fluorescence property has made Dansyl dyes an important tool for biophysical studies. They are particularly useful for preparing fluorescent drug or ligand analogs that are expected to bind to hydrophobic sites in proteins or membranes or other biological receptors. Dansyl protein conjugates have fluorescence lifetimes of 1020 nanoseconds.