how to confirm the presence or absence of very small dna (if below

Vince Mulholland via methods%40net.bio.net (by Vince.Mulholland from sasa.gsi.gov.uk)
Thu Feb 4 04:06:45 EST 2010


Uday,

The only thing that I can suggest is to use an assay for the detection of deoxyribose 
developed by Ken Burton in the 1950's. This is a spectrophotometer-based colorimetric 
assay which uses the reaction of deoxyribose with diphenylamine and is specific for DNA; 
it will not detect RNA (except when the RNA is present at very high concentrations).
There are more recent assays, but this is the most well known.

Burton, K (1956) A Study of the Conditions and Mechanism of the Diphenylamine Reaction 
for the Colorimetric Estimation of Deoxyribonucleic Acid. Biochem. J. 62: 315-323.

Good luck,

Vince

Vincent Mulholland
Molecular Biology Unit Manager -  Diagnostics & Molecular Biology Section
Science and Advice for Scottish Agriculture (SASA)



hi

I purified my protein under acidic conditions pH-4 with the reason that it
will be free from dna. even though its 280 absorption dominates the 260
absorption the 280/260 ratio is always 1.2.

I would doubt that there is some DNA but i could not see any signal on
agarose gel. I am also sure that the DNA is not homogeneous as it is
overexpressed in E.coli which is not a native host.

My concern is to confirm the presence or absence of DNA in the sample.

I also tried Mass spectroscopy. its a failure because of some unknown
reason.

could you please suggest me any method that can prove the presence or
absence of DNA. It would be nice if it is other than mass spectroscopy and
radio labeling.

-- 
With Regards
uday
(u.kumar from fz-juelich.de)






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