It has a semi-structural formula (C2H4AsS2)2-(C13H5O3)-C6H4COOH, representing the dithiarsolane substituents bound to the hydroxyxanthone core, attached to an o-substituted molecule of benzoic acid.

FlAsH-EDT2 is used for site-specific labelling, selectively binding to proteins containing the tetracysteine (TC) motif Cys-Cys-Xxx-Xxx-Cys-Cys and becoming fluorescent when bound.

[5] Such strong sulfur-arsenic bond can be, again, regulated by designing a peptide domain that exhibits higher affinity toward the arsenic, such as tetracysteine motif.

The quantum yield is 0.49 for 250 nM FlAsH is bound to a model tetracysteine-containing peptide in a phosphate-buffered saline at pH 7.4.

[6] Generally, FlAsH-EDT2 has 0.1-0.6 fluorescence quantum efficiencies with several μM detection limits for diffuse cytosolic tag and 30 - 80 extinction coefficients L mmol−1 cm−1.