Q: Checking DNA purity using spec...

Biol. Cel. bc2biced at lucano.uco.es
Tue Nov 26 11:14:17 EST 1996

Otter wrote:
> I have been using the standard protocol to determine isolated DNA purity by
> measuring the light absorbance at 260 and 280 nm.  I know that pure DNA
> absorbs at a wavelength of 260 and protein at a wavelength of 280.  My
> questions is what exactly or specifically is absorbing the light at those
> wavelengths (i.e. does one base absorb more light than another at 260, are
> there specific amino acids that are absorbing at 280 etc...)?
> Thanks for your time and help,
> Otter

I only have some data about this but it can help you. GMP has a MW of
425 and the relation DO 260/mM is 12, or DO260/ug/ml is 0.03, for AMP is
383, 15.2 and 0.04 respectively, for TMP is 322, 8.4 and 0.025 and
finaly, for CMP is 403, 7.0 and 0.02. With these data relationship
between º/1 results in the relation
I hope this could help you. About peptides and aminoacides I haven't got
any data.

Guillermo López-lluch
Facultad de Ciencias
Universidad de Córdoba.

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