I have a quite simple problem
Recently I've run the gel: it was prepared as 12% denaturing SDS PAGE gel. But it didn't look like 12% (it looked as it was more concentrated). Also during transfer to membrane (Western blot) bigger proteins weren't transfered completely. And eventually I had lateral band spreading during electrophoresis (visible on my page ruler) and also on my membrane after signal detection.
I've repeated this experiment - the same samples but on a new gel and then everything went fine.
So question is - what was wrong with the first gel? It polymerized normally. I'm thinking - maybe I added wrong Tris (usually lateral bands spreading results from incorrect salt concentration)?
Will be much grateful if you could help me to explain this