Atto 665 is a fluorescent dye similar to Atto 647N, featuring strong absorption, high fluorescence quantum yield, and excellent stability against heat, light, and ozone. It maintains consistent absorption and fluorescence across pH levels from 2 to 11. This hydrophobic, cationic dye carries a net +1 charge when attached to a substrate and is best excited by light in the 640 - 675 nm range, using sources like a 647 nm Krypton-Ion laser or a 650 nm diode laser. Atto 665 is usually coupled to DNA and RNA oligonucleotides.

Figure 1. Structure of 5'-Atto 665 (R = sequence).
metabion offers Atto 665 (Figure 1) in its DNA and RNA portfolio as a 5'-, 3'- or internal Atto 665-dT modification: