Inhibitory oligonucleotides compete with the molecular beacon. Inhibition of fluorescence increases with addition of different oligonucleotides. αCP2, at a concentration of 0.05 µM, was preincubated overnight with various excesses of sense DNA oligonucleotides [filled circle, poly(C); open circle, S33; cross, S28; filled box, S40; open box, mutant 2; filled triangle, poly(G)] from a 64-fold excess over αCP2 to equimolar ratios.