ATTO 637 belongs to a new generation of fluorescent labels for the red spectral region. Characteristic features of the label are strong absorption, high fluorescence quantum yield, high thermal and photostability, and only little triplet formation. The dye is very stable under physiological pH-values and in buffers up to pH 8.5. However, it slowly degrades at higher pH.

ATTO 637 and its derivatives are supplied as crystalline solids. Although very similar to ATTO 635, ATTO 637 is more hydrophilic and better soluble in water. After coupling to a substrate the dye moiety is electrically neutral. For details of coupling see our recommended labeling procedure (PDF). The fluorescence is excited most efficiently in the range 605 - 650 nm. Suitable excitation sources for ATTO 637 are the 633 nm line of the He:Ne Laser or a Diode-Laser emitting at 635 nm.