Dye	Abs (nm)	Em (nm)	ε (M-1cm-1)	QY
ATTO 390	390	479	24.000	90
ATTO 425	436	484	45.000	90
ATTO 465	453	508	75.000	55
ATTO 488	501	523	90.000	80
ATTO 495	495	527	80.000	45
ATTO 520	516	538	110.000	90
ATTO 532	532	553	115.000	90
ATTO 550	554	576	120.000	80
ATTO 565	563	592	120.000	90
ATTO 590	594	624	120.000	80
ATTO 594	601	627	120.000	85
ATTO 610	615	634	150.000	70
ATTO 611X	611	681	100.000	35
ATTO 620	619	643	120.000	50
ATTO 633	629	657	130.000	64
ATTO 635	635	659	120.000	25
ATTO 637	635	659	120.000	25
ATTO 647	645	669	120.000	20
ATTO 647N	644	669	150.000	65
ATTO 655	663	684	125.000	30
ATTO 665	663	684	160.000	60
ATTO 680	680	700	125.000	30
ATTO 700	700	719	120.000	25
ATTO 725	729	752	120.000	10
ATTO 740	740	764	120.000	10
Abs = absorption maximum#, Em = emission maximum#, ε = molar extinction coefficient, QY = fluorescence Qantum Yield# # in water

ATTO Dyes are a series of fluorescent labels and dyes manufactured by ATTO-TEC GmbH in Siegen, Germany. The dyes have been designed for application in the area of life science, e.g. labeling of DNA, RNA and proteins as well as analytical applications, in particular fluorescence microscopy.

The ATTO Dye series covers a spectral range from 390 nm in the UV up to 740 nm in the near infrared allowing excitation with most commonly used light sources. The dyes typically are derivatives of coumarins, rhodamines, carbopyronins and oxazines. They are commercially available as free carboxylic acids, amine reactive N-hydroxy-succinimidyl-esters (NHS-ester) or thiol reactive maleimides.

Many common fluorescent labels, e.g. Fluorescein (FITC), show rather low photostability. As a result sensitivity and quality of imaging are limited if high-intensity laser excitation is used and processes are to be observed over long periods of time. This is a serious draw-back in microscopy and other techniques based on the confocal principle, e.g. in single-cell detection applications. In contrast to some widely used older dyes, the patented ATTO-labels are designed to be much more stable under prolonged irradiation.

Compared with other labels especially for the red region of the spectrum, ATTO-labels show excellent photostability and brightness. ATTO 647N fluoresces twice as strong as Cy5 in aqueous solution.^[1]

In addition many common fluorescent labels especially cyanine dyes like Cy5 deteriorate even without any irradiation (in the dark), in particular when exposed to small concentrations of ozone present in the laboratory atmosphere.^[2] Under identical conditions of ozone exposure the new dyes ATTO 633, ATTO 647N and ATTO 655 last up to 100 times longer than cyanines like Cy5 and Alexa Fluor 647.^[3][4] This is very important in microarray applications, where the dye molecules are located at the surface and thus are in direct contact with the atmosphere.

The Alexa Fluor dyes from Invitrogen, the PromoFluor Dyes from PromoKine, the Hilyte Fluor dyes from AnaSpec and the DyLight Fluor dyes of Thermo Fisher Scientific are similar lines of fluorescent dyes and are alternatives to the ATTO Dye series.

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