use much less primer,Start with 1/4 and 1/8th the amount you are using. Ideally use a hot start enzyme but if you do not have any then do not allow the enzyme and primer mix to stay together for too long before starting pcr cycling, Prepare the reagent pcr mix on ice and then transfer the tubes straight onto the pcr machine and start cycling immediately, It may be necessary to redesign the primers but try less primer first. You often get worse primer dimer when the pcr does not work. This can sometimes happen when using poor quality dna that does not amplify. Borrow some dna from a colleague that has amplified with other primers to test your primers against a good dna

use much less primer,Start with 1/4 and 1/8th the amount you are using. Ideally use a hot start enzyme but if you do not have any then do not allow the enzyme and primer mix to stay together for too long before starting pcr cycling, Prepare the reagent pcr mix on ice and then transfer the tubes straight onto the pcr machine and start cycling immediately, It may be necessary to redesign the primers but try less primer first. You often get worse primer dimer when the pcr does not work. This can sometimes happen when using poor quality dna that does not amplify. Borrow some dna from a colleague that has amplified with other primers to test your primers against a good dna

We had this problem before. We decrease concentration of primers during mixture. Also should chech the dimer delta g value using signa Aldrich software.

Regards

Maximiano

Sometimes primer dimers may be due to a higher ionic strength within the PCR mix. If possible try changing the concentration of Mg2+.

You might need to redesign primers. Conduct in silico PCR for the primers you design and analyze carefully before finalizing primers. You might also need to analyze a few other parameters through oligo analyzer for safe side to see the efficiency of primers.

Also, DNA might have some contamination in common.

Thank you paul, Antonio, Hasanka

I will try again amplification with decrease of primer concentration

How can I download signa Alderch software? and what about delta g value

you should decrease the concentration of primer used, you can also use idt primer designing tool for delta g value (more negative value=less primer dimer) in case you are not able to download sigma software.

you can run your product for longer because the primer dimer bands get light with the long run and disappear.

I hope this helps.

Thank you Laraib

Do you mean that I run product for long time in the gel electrophoresis or during amplification by PCR machine?

The product is to be run for longer duration in gel electrophoresis. The primer dimer bands will not show up.

I have encountered this problem several times. My best advice will be to proceed with something called gradient PCR. More often than not, this problem arises because we don't precisely know the optimum primer annealing temperature for PCR. If you have designed your primers accurately (they shouldn't self anneal and shouldn't make secondary structures), and you are using it at the right concentration (it is also very important), then gradient PCR can most probably solve your problem. You can read more about gradient PCR here : http://www.bio-rad.com/webroot/web/pdf/lsr/literature/Bulletin_5633.pdf

as Rajat Kumar Jha mentioned I agree with him. you can use gradient PCR. the temperature showing the lightest dimers along with the sharp PCR bands should be used further Hayder Ali

Try to reduce the amount of primers you add , or increase the annealing temperature.

Increasing the annealing temperature by as little as ONE degree sometimes makes the difference in my pcr failing or not or producing a tiny yield.

Hi ... Besides all the recommendations already posted, I would suggest you to include DMSO in the reaction mixture. Concentrations from 6 to 12% are possible. This additive is useful for primers with high GC content.

Good luck. Best

I am finding that the Touchdown Pcr protocol is solving a lot of my problems