What am I doing wrong?
In the process of gel electrophoresis (using if for proteins), why do actin and myosin only show on the muscle tissue and not on other tissues like the liver?
I see no one addressed your question, so I’m going to attempt to do it.
Both Actin and Myosin are mostly found in muscle tissue, as they are the building blocks of muscle fibre. So you will likely not find Actin and Myosin in the liver tissue.
I’ve used SDS-PAGE method on crude mitochondria and the reason why I saw Actin and Myosin as parts was because of a very simple reason - I’ve had muscle fibres contaminate the prep. Even with a Coomassie Brilliant Blue staining, it’s unlikely you’ll detect Actin and Myosin in a gel electrophoresis for the liver, if the protein concentration is very low.
What you can do though, is to do a western blot (protein immunoblot) and probe with antibodies. One more thing to note, and perhaps you’re aware already, there are several different myosin proteins, which means that the myosin in liver cells might not cross-react with antibodies against muscle myosin. They might also have enough of a difference in their molecular weight so you don’t actually recognise their band by mobility.
Good luck with the rest of your work!