Deep Dark Quencher I (DDQ I, Figure 1) is a dark quencher often used in dual-labelled probes.
As dark quenchers, DDQ I absorbs energy without emitting fluorescence. It is in fact a non-fluorescent chromophore quenching the lower wavelength dyes such as FAM (absorption max. ca. 440 nm). As such, its quenching properties are very similar to that of Dabcyl and overlaps, to some degree, with BHQ-1®.
Figure 1. Structure of 3'-DDQ I (R = sequence).
metabion offers DDQ I in its DNA and RNA dual-labelled probes portfolio: