Nanodrop question for RNA - (Jun/10/2014 )
I have got a reading from RNA extracted sample with the following
A260/280 = 2.08
A260/230 = 2.26
A260 = 14.924
A230 = 7.191
Do these readings show good RNA?
does anyone know? I believe readings are good but some websites say 260/280 = 1.8-2, and 260/230 of 2.0, so I wanted to get other opinions on RNA.
I think your absorbance values are fine. From my experience, having an OD260/OD280 of 2.0 is clean RNA; I would be hesitant to use anything less than 1.8. If you're in doubt, I would suggest running a denaturing gel and check what you see there.
Looks fine to me as well. The 280/260 is roughly within range, and as for the 260/230 I'd rather be worried about too low values anyway (contamination).
The absorbance readings depend on the solvent - if you used water, then 1.9-2.0 is the accepted range for 260:280, but values differ for different buffered systems.
bob1 on Thu Jun 12 21:04:22 2014 said:
The absorbance readings depend on the solvent - if you used water, then 1.9-2.0 is the accepted range for 260:280, but values differ for different buffered systems.
Bob1, could you elaborate a bit on this? I'm definitely no nanodrop expert (I use TE or water only) and thought that blanking with the buffer/solvent would eliminate much of the differences. What accounts for the difference in ranges? Thanks!
I can't remember exactly but I think something to do with protonation of the purines and pyramidines of the DNA.
I just remembered this TechNote.
I have a similar, I have no experience with nanodrop, but I have extracted DNA using the QIAGEN kits and the 260/280 results range from 2.6-3.3. And the average DNA concentration is 122946 ug/ul
I'm not sure what to make of those numbers, since they are higher than usual.
Truz89 on Thu Jul 10 15:51:11 2014 said:
I have a similar, I have no experience with nanodrop, but I have extracted DNA using the QIAGEN kits and the 260/280 results range from 2.6-3.3. And the average DNA concentration is 122946 ug/ul
I'm not sure what to make of those numbers, since they are higher than usual.
Check the DNA on a gel - results like that usually indicate contaminants of some sort.
The curve shown by the nanodrop should give you some idea if the samples are clean.
Incidentally, the nanodrop measures in ng/ul not ug/ul...