need: info on A260-A280 absorbance measurements

[Manuel G. Claros]

On 14 Oct 1996, Guido Hooiveld wrote:

 > I was told an A280/A260 ratio

Note: A260/280

 > theoretically limit is 2.0. However, I often find a ratio larger than 2.0; like 2.1 to 2.2. So, 
 > is this (theoretically) value of 2.0 correct, if yes, does anybody have a suggestion why I find 
 > values >2; if not, what is this value? 

You have degradated nucleotides.

 > multiply A260 with 50 to obtain the concentration (ug/ml), or use 35? Which value is correct?

50 for oligonucleotides and 35 for dsDNA

 > Any comments would be appreciated!

I hope this helps

Manuel G. CLAROS, Ph.D.
Bioq. & Biologia Molecular
Fac. Ciencias
Campus de Teatinos
E-29071 Malaga