Help with Maxiprep plasmid low ratio - (Jan/24/2008 )

Hi,

I am using the Nucleobond maxiprep kit. I started doing maxipreps only recently.
The first time I did, I got average yield (about 200 ug from 250 ml culture broth). But my ratio was around 1.4.
And that is a problem since I am going to use these for transfection.

I repeated the maxiprep. made sure my culture were grown not more than 12 - 13 hours.
Took extra care not to break or handle the pellet too rough.
At the end, I still have a low ratio of around 1.4. and my yield is also not all that great..

I am not sure what I am doing wrong.. Why am I getting a low 260/280 ratio every time ??

Please help !

For some cases, its better to precipitate DNA after eluting from maxi kit. You should have cleaner DNA after precipitation.

Are you rinsing the pellet with ethanol and allowing it to dry COMPLETELY? This takes a long time with a maxi pellet, but if you don't do it, you'll have alcohol contamination in your DNA, which affects its purity and obviously OD as well.

Ginger