Working with a new qPCR target
When looking at a new target of unknown expression level, the amount of RNA required to detect the target of interest depends on the abundance of the target in each sample. For high-copy-number transcripts you may be able to detect in as little as 10 pg, while for low-copy-number transcripts you may require more than 100 ng.
With all new targets (new sets of primers or new qPCR kits), a 10 fold serial dilution should always be run, to validate both the slope and the limit of detection (LOD) (the highest Ct value observed for a truly positive sample, as verified by melt-curve analysis). Only a single peak, which represents the specific PCR product, should be observed on the melt curve, the presence of other peaks indicates the presence of primer–dimers and/or nonspecific PCR products which can contribute to a stronger fluorescence signal and an earlier Ct, but will not be as sensitive.