We have been using the Qiagen high speed maxi prep kit to isolate
plasmid DNA for a while and have had some problems. We have
standardized our growth time and pretty much always prep high copy
plasmids such as PcDNA. The problem is that sometimes we get 1 mg of
DNA and sometimes we get no DNA at all! My wife (in a separate lab)
has also had this problem and they did a side by side comparison (2
different columns, same cultures, etc) and one had 0.8mg and the other
no DNA. Has anyone else had a similar yield problem with this kit?