This has been discussed here many time in the past. You can search this
newsgroup's archive at e.g. http://groups.google.com. Most probably you
have too much salt in your sample and should dialyze your sample prior to
boiling. Check for example this document (p.11)
Reducing the sample volume might also help a bit.
"Katrin Westphal" <k.westphal at uni-bonn.de> wrote in message
news:3D73541D.F664307E at uni-bonn.de...
> I have problems with my SDS-PAGE: The bands grow wider the further they
> have run and the resolution grows bad: bands at the the top seem to be
> ok, while those at the bottom are blurred and much bigger than the ones
> My samples are bacterial membrane proteins or whole cell extracts in
> sodiumphosphate buffer.
>> Thanks in advance for any help!