DNA-conc. in solutions

Hiranya S. Roychowdhury hroychow at nmsu.edu
Mon Feb 21 17:07:15 EST 2000


Interference from proteins (and polysaccharides) may be dealt with in the
following equation:

[N] = 49.1*A260 - 3.48*A230


The ratio 260/230 ranges from 2.2 for DNA to 2.4 for RNA.
I hardly ever use this formula, since the source of the NA seems to have a
bearing on the outcome . Not surprising, since the absorbance of NA's will
most certainly depend on the base composition. Same thing is true for
proteins, where the specific variations are even greater due to the greater
variability of aa compositions. 
Thus, the averaged extinction coefficients of individual nucleotides for the
nucleic acids have come to be accepted as standards. 




At 10:42 AM 2/21/00 GMT, a_firzinger at my-deja.com wrote:
>I usually measure DNA-conc. by determining OD at 260nm and
>280nm. Usually I assume 50µg/ml ds DNA at OD260 of 1.
>However, I know that there is a formula existing, which
>includes the OD measured at 280nm. Maybe someone of you
>remembers it and could send it to me. I just know a
>formula for protein concentration which includes
>OD260nm and 280nm:
>Prot.conc.(mg/ml)= E280 x 1,56 - E260 x 0,757
>
>Regards,
>
>Andreas :-)
>
>
>Sent via Deja.com http://www.deja.com/
>Before you buy.
>


Dr. Hiranya Sankar Roychowdhury
GENE LAB/ EPPWS
New Mexico State University
Las Cruces, NM 88003
Ph. (505) 646-5785
hroychow at nmsu.edu

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