insoluble DNA pellet after Qiagen Tip20

In article <eggermon-200694162025 at 134.58.181.40>,
eggermon at popserv.kuleuven.ac.be (Jan Eggermont) wrote:

> Last week I tried Qiagen Tip 20 columns to prepare some DNA. It all went
> fine until the very last step. After the isopropanol precipitation and the
> ethanol 70% wash there was a small pellet visible at the bottom of the
> tube. However, I could not resuspend this pellet in TE. I tried all sorts
> of tricks such as vortexing vigourously, increasing the volume of TE to 100
> microliters, heating to 50 0C, but to no avail. I then 'reprecipated' the
> pellet, washed it extensively with EthOH 70%, but the final pellet was as
> resistant to resuspension as the first one (despair....).
> 
> Has anyone experienced similar problems with the Tip 20? Any help,
> suggestions and tips are greatly appreciated...
> 
> PS: I have also used the Tip 100 colums which worked fine. No problems in
> resuspending the final pellet.

Hi Jan

Sounds to me like you overloaded the column with too much bacteria and/or
didn't wash enough of the protein (it is your insoluble material) away.
They warn you about this in the directions. Just use less. 

Steve Coon
sdcoon at umich.edu
University of Michigan Medical Center