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 modification in its DNA portfolio:
Suggestions
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 modification in its DNA portfolio: