Single Plasmid Gel Band - (Sep/18/2012 )
Can (in any misterious special conditions) a non-digested plasmid appear as a single band (without the coiled states) in a ordinary agarose electrophoresis gel!?
I heard this rumor by a colleague and didn't found anything consistent in the literature.
Personally, I think that it not make much sense. Any thoughts or experiences!?
Sure, if the plasmid wasn't prepared properly. Dring alkaline lysis it can be nicked by the conditions, shearing of the DNA by over-vigorous shaking, vortexing or pipetting can also damage the DNA.
It is pretty uncommon though, I would still expect to see both nicked and linear forms.