Low sized bands in plasmid preperations - its not RNA! (May/13/2009 )
10 ul of 10ng/ul is 100ng.it's not that high. and most of the MW is contributed by heavy molecular weight molecule ( the one at the high end) while the low end is small thus getting less binding to the extend that u can't see it.
I just wanted to say that disappearance of the upper bands (relaxed plasmid) and persistence of the lower band in the dilute sample can not be because of lowering of the intensity due to dilution. Isn't is quite logical? 
Problem located!
That extra band was coming from the lab-made loading dye; donno how 
We just loaded only the loading dye in agarose gel n the same band was there! Can it be because of some microbial growth in the dye containing just glycerol, bromophenol blue and water?
ram on Jul 19 2009, 07:10 PM said:
That extra band was coming from the lab-made loading dye; donno how
We just loaded only the loading dye in agarose gel n the same band was there! Can it be because of some microbial growth in the dye containing just glycerol, bromophenol blue and water? maybe its a DNA contam. That is, someone has used the sample loading tip in the loading dye and introduced the sample into the dye!