The 5-isomer of TAMRA™ has a similar spectral property to 6-TAMRA™. 5-TAMRA™ is attached to an oligo through the copper (I) catalyzed alkyne-azide click reaction. The internal version of this modification is attached to the oligo through a dT base. Incorporation of the internal version will add a dT nucleotide at that position. To avoid adding an extra nucleotide, replace an existing T nucleotide in your sequence with the required modification.