Probiotics and Prebiotics
New publication 2015 ...
Acidophiles, Thermophiles, Halophiles ...
Current Innovations and Future Trends
Download flyer
Current and forthcoming books

Potassium Chloride Concentration

Potassium chloride (KCl) is normally used in a PCR amplification at a final concentration of 50mM. To improve the PCR amplification of DNA fragments, especially fragments in the size range 100bp to 1000bp, a KCl concentration of between 70mM and 100mM is sometimes recommended. For the amplification of longer products a lower salt concentration appears to be better. But the PCR amplification of short products works better at higher salt concentrations. This is probably because an increase in salt concentration permits shorter DNA molecules to denature preferentially to longer DNA molecules. Shorter molecules are therefore amplified better at higher salt concentration. It should be remembered however that a salt concentration above 50mM can inhibit the Taq polymerase.
Real-Time PCR
Edited by: Nick A. Saunders and Martin A. Lee
Provides both the novice and experienced user with an invaluable reference to a wide-range of real-time PCR technologies and applications and supplies detailed technical insights into the underlying principles, methods and practice of real-time PCR.
"an invaluable reference" (Doodys); "wide range of real time PCR technologies" (Food Sci Technol Abs); "I was impressed by this text" Aus J Med Sci read more ...

If you are finding unwanted, long, non-specific products an increase in KCl concentration may reduce the appearance of these products. Similarly, to get rid of short, non-specific products you can decrease the KCl concentration to about 35 or 40mM. In either case do not change the MgCl2 concentration. To improve the yield of a product you can try adjusting the KCl concentration: increase it for a desired product less than 1000bp; lower it for a desired product greater than 1000bp.

Further reading:

  1. PCR Books
  2. PCR Troubleshooting and Optimization: The Essential Guide
  3. Real-Time PCR: Current Technology and Applications
  4. Real-Time PCR in Microbiology: From Diagnosis to Characterization
  5. PCR Troubleshooting: The Essential Guide