I am using primers having 60bps of overhangs in addition to the actual annealing region of around 22nts, thereby making my primers some 80-82nts long. When I am using these primers I get right size of amplicon but with very low intensity and hence the problem starts. Can anybody suggest how to improve my PCR using these primers?
Long primers can be ineffective for various reasons, f.ex. they may anneal to unwanted sequences. In case you already have tried to optimize your PCR (MgCl2, annealing temp, primer concentration etc.) and checked your primers for self-annealing/ dimer formation, I would suggest considering the following. Do a two-step PCR using only the actual annealing ~22bp primers in the first round, e.g. 15 cycles or so. For the next step, take a small aliquot of the first round product (1 ul or less by further dilution) as template for the second round PCR (maybe 25+ cycles) with the overhang primers. This way you would enrich your target while diluting the first round primers to a minimum. Touchdown PCR might also help.
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