Cloning purified PCR products eluted in Qiagen's EB - Concentrate a purified PCR product eluted with EB? (Jan/31/2009 )

Hi all,

I gel extract and purify my PCR products using Qiagen's Qiaquick kit and elute with 30 ul of elution buffer (EB). How much can I concentrate this eluted DNA in EB using a vacufuge before the salts in the buffer will negatively affect the ligation reaction?

Thanks!
Kevin

EB is 10 mM tris-HCl. If you concentrate 10x and then use 1 ul in a 10 ul ligation, you will be adding 10 mM tris-HCl to the buffer, which probably won't make much of a difference. Usually you don't want high DNA concentrations for ligation, so I'm not sure why you would want to do this. High concentrations favor long concatamers rather than recircularization, reducing the DNA fragments that will actually transform.

Hey

I use freshly autoclaved water to elute, saves me from all these problems and the DNA is also stable. Atleast for 5 years at -20 degrees.

Best
TC

Elution depends on the pH of the elution buffer, which should be slightly alkaline. Pure water has an uncontrolled pH, tending to the acidic as it absorbs CO2 from the atmosphere. You could dilute the 10 mM Tris to 1 mM, and still control the pH effectively.

Thank you for the replies. I have a few PCR products that produced faint bands that I gel purified. I am using Promega's pGEM-T cloning kit so I want to use as much of my product for the ligation as I can.

i was using Vivantis GF-1 Nucleic Acid Extraction Kit to purify my DNA.....
however i was in a dilemma during the last step, i.e.: elution of DNA..

i was supposed to use the EB (elution buffer) to elute, however, the sequencing company that i would send to, request me to store my purified DNA in water.

so which one does matter ? as mentioned above, water might have uncontrolled pH, while EB has slightly alkaline pH...

any comments, pls ?
thank you.

tyrael on Feb 12 2009, 01:56 PM said:

I have always used water to be on the safe side and have had some really nice results. And surely the content of CO2 would be low in autoclaved water and therefore wont stay dissolved?

Kami23 on Feb 12 2009, 06:02 AM said:

actually due to the pressure and lack of buffering, freshly autoclave is a little acidic around pH5.
Water which has time to equilibriate with the atmosphere has a pH of around 5.6.

if that so, autoclaved distilled water is stil slightly acidic....
hmm, i better do a pH value check before i elute it with water.

DNA stored in EB wil last longer than water ? or it's the same ?

tyrael on Feb 12 2009, 07:45 AM said:

DNA in EB would probably last longer as it contains tris-HCl buffer. How much longer would the prep be useful is dependent on how much DNA was present initially and is it ssDNA or dsDNA.