Concentration of DNA

Paul N Hengen pnh at
Fri Nov 22 16:52:59 EST 1996

fang at SASK.USASK.CA wrote:

> Dear netter,
> How do you measure DNA concentration accurately? By gel (agarose or 
> acrylamide) or by spectrophotometer? What is the lowest concnetration you 
> can get? Say the DNA is 500 - 1 kb in size. How do you measure very low 
> concentration, eg. around 5 ng/ul, and you could not afford 1 ml of DNA 
> sample for measureing? 
> Thank you very much in advance. 
> Li 

Dear Li:

I just demo'ed a TD-700 fluorometer from Turner Designs (Sunnyvale, CA).
I was able to detect 1-2 ng/ul of pUC19 DNA with the dye PicoGreen from
Molecular Probes (MP). The standard curve I made was linear in the range of
1-100 ng of DNA, and estimations of DNA in the range of 10-100 ng were best.
Although MP claim you can read down to 25 pg of DNA, for me, below 1 ng was
not very good because there was variability in the raw fluorescence at that
point. I had no problem measuring 5 ng/ul samples, however. If you can spare
1 ul of your DNA and know someone with a fluorometer, I recommend to do it
this way. If all you can do is a spot test, I'd look into a PicoGreen dye kit
from MP. Their address is on the FAQ list for this group.

* Paul N. Hengen, Ph.D.                           /--------------------------/*
* National Cancer Institute                       |Internet: pnh at |*
* Laboratory of Mathematical Biology              |   Phone: (301) 846-5581  |*
* Frederick Cancer Research and Development Center|     FAX: (301) 846-5598  |*
* Frederick, Maryland 21702-1201 USA              /--------------------------/*
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