BHQ®-2 (Figure 1) stands for Black Hole Quencher 2 and it consists of a dark quencher, often used in dual-labelled probes. As dark quenchers, Black Hole Quenchers absorb energy without emitting fluorescence. They are in fact non-fluorescent chromophores.
Figure 1. Structure of 5'-BHQ®-2 (R = sequence).
metabion offers BHQ®-2 in its DNA and RNA dual-labelled probes portfolio: