ATTO 520 is a fluorescent label similar to the widely known dye Rhodamine 6G. Its key characteristics include strong absorption, high fluorescence quantum yield, and excellent thermal and photostability. The dye is somewhat hydrophilic and, at pH levels above 7.0, exists in equilibrium with a colorless form (pseudobase). This reversible reaction does not affect its ability to couple with molecules. When the pH is lowered, absorption and fluorescence are completely restored. The dye is most efficiently excited within the 510 - 535 nm range, with an Argon-Ion laser at 514 nm being an ideal excitation source.
Atto 520 (Figure 1) is spectrally similar to CAL Fluor® Gold 540 and can therefore be used as its alternative.
Figure 1. Structure of 5'-Atto 520 (R = sequence).
metabion offers the Atto 520 in its DNA and RNA portfolio (as a 5'-, 3'- or internal Atto 520-dT modification):