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2 week old maxiprep DNA smearing - (Nov/16/2007 )

I made a plasmid DNA (~9KB) maxiprep about two weeks ago (was stored in 4 deg C for around two weeks and then was moved to -20 recently). Its concentration is around 2 ug/ul and it shows some smearing when I run in on a 0.7% agorose gel. Is this normal for such high concn DNA? I ran 1 ul of this sample in the gel. Thanks in advance for any feedback.


Smearing is normal if too much DNA is loaded on the gel. How much DNA are you running on the gel, and how far does the smearing go?

-bitesizebio guy-

here is an image I grabbed after running it for a bit:

I loaded 1ul of the DNA prep.



that' s fine. From the looks of the picture the smearing is probably caused by to much DNA.

The kind of smearing to fear is when the tail of the smear points downwards. A down ward pointing smear means that the DNA is degrading. Upward pointing smear on the otherhand could mean several things; overloaded well, bacterial genomic DNA contamination, salt contamination, or the gel was run too fast.


Its just too much DNA in the well, as others also guessed.

2ug of DNA is too high. For simple DNA analysis, we were told to load not more than 100ng of DNA per well.