Probe sequences used in - and representative images from - non-denaturing FISH experiments. Cy3INV: sequence-matched Invader, Cy3INVmm: fully base-paired but triply mismatched Invader, and Cy3DNA: unmodified analogue of sequence-matched Invader. Images viewed using Cy3 (left) or DAPI (right) filter settings. A, C and U denote 2'-O-(pyren-1-yl)methyladenosine,[49] 2'-O-(pyren-1-yl)methylcytidine[49] and monomer Y, respectively. Conditions: 38.5 °C, 10 mM Trizma®-HCl, 50mM KCl, pH 8.3, 60 min (Cy3INV) or 180 min (Cy3INVmm/Cy3DNA) incubation. Samples visualized using a fluorescence microscope at 400× magnification.