Dansyl-X modification is a post synthesis conjugation to a primary amino group. The amino group can be placed at the 5' and 3' and for internal positions an amino modified base is used, e.g Amino dT C6
Dansyl-X NHS dye is a post synthesis conjugation dye requiring an amino group on the oligo. The amino group can be placed at the 5' or 3' or any internal position using amino C6 base. Ideally we recommend to use amino C6- dT or U for RNA oligo.
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 10-20 nanoseconds.