PBlue fluorescent dye 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

PBlue is a UV-excitable, bright blue fluorescent dye used for labeling oligonucleotides excitable by the 407 nm spectral line of blue diode (violet color) laser. PBlue has an absorbance maximum of 401 nm and an emission maximum of 421 nm. Because UV light can photo damage labeled oligos, and many kinds of cells and tissues autofluoresce under UV light, PBlue can only be used in a limited number of applications. Nevertheless, for such applications as nucleic acid microarrays and in situ hybridization, where a blue fluorescent probe provides a easily distinguishable, contrasting color to the green, yellow, orange and red fluorescence produced by longer-wavelength probes, PBlue can be a good choice.