The Alexa Fluor 647 Oligonucleotide Amine Labeling Kit provides a simple method for labeling amine-modified oligonucleotides with our intense, far-red—fluorescent Alexa Fluor 647 dye (spectrally similar to Cy5 dye). Oligonucleotides labeled with this kit can be used as primers and as probes in hybridization experiments but should not be used for automated DNA sequencing since the Alexa Fluor dye in the kit is supplied as mixed isomers. The kits have been optimized for labeling reactions with 50 µg of a 5'-amine—modified oligonucleotide, 18 to 24 bases in length. Fluorescence of this long-wavelength Alexa Fluor dye is not visible to the human eye but is readily detected by most imaging systems.