Comparison of the photobleaching rate of the thiacarbocyanine dyes with substituents of ethyl, propyl, butyl, pentyl, and pyridinium, (corresponding to DiSC2(3), DiSC3(3), DiSC4(3), DiSC5(3), and DiSCpy(3), respectively). The label on the X axis shows the amount of M. tuberculosis (MTB) genomic DNA in each reaction. The PNA probe used here is TB14, sequence shown in S1. The final concentration of PNA in the 50 μL reaction is 160 nM. All dyes had a final concentration of 9 μM. The buffer is 10 mM homopipes, pH 5.0, 0.05% Tween 80.