"Mickey Mouse" bands - (Oct/05/2012 )
It sounds like it might be a salt problem, but could you post a picture so we can be sure of the effect you are talking about
Does it occur consistently in the sample(s) that you have seen it in?
Are you boiling the samples for 5 min, or is it a lower temp?
You may be lysing your cells at too high a concentration - what volume is the 25 ug in?
It does not happen with all samples, despite the fact that I prepare them in the same manner.
I only heat my samples for five minutes. I do not boil them.
Twenty-five micrograms of protein is usually in a volume of 12-20 microliters.
Does the odd band formation happen in those samples with lower volume (i.e. higher concentration)?
i suspect that you are seeing some sort of aggregation/complex formation which is resulting in retarded migration. If you can, try boiling for 5 min or heating to 70 C for 10-15 min, one of the samples that consistently does this - this should denature the samples completely in the presence of SDS and a reducing agent.