Hi,

I have been isolating some plasmids from E. coli for routine use (like PBBR1MCS), but I have a problem accurately quantifying the DNA that I get.. I used the Qiagen miniprep columns for 5 ml overnight culture, and for 15 ml cultures I did exactly the same, but precipitated the DNA from the supernatant with NaAc and isopropanol.. In the first case I have maybe a concentration of 60 ng/ul in 50 ul but I see nothing on the gel, even if I load some 5 ul..In the latter case the Nanodrop says that I have appr. 500 ug of plasmid (which is not very feasible, I know) but when I load it on the gel, I can definitely say that it is not 500ug, perhaps 1:10th of it in total but I cannot say exactly how much. I could try to do single digest, precipitation and gel comparison maybe even with a software, but this is really time consuming.. anybody have a better idea how to overcome this Nanodrop anomaly?

Thanks!

basak