Dabcyl (Figure 1) is a dark quencher often used in dual-labelled probes. The 3’-terminus of Dabcyl consists of a free OH. When Dabcyl is inserted at the 3’-end of a primer/probe, the polymerase can theoretically elongate the primer/probe. However, the efficiency of this elongation is rather low.
Figure 1. Structure of 5'-Dabcyl (R = sequence).
metabion offers Dabcyl in its DNA and RNA dual-labelled probes portfolio: