calculate the isoelectric point of a protein. I understand that you need to substitute variations of pH until you find a pI that is close to zero. What I need is a detailed example of the process for a simple protein (say 4 amino acids, preferably charged). It would be helpful if you could also provide a similar protein and answer only so I can check my understanding. It would also be helpful if you could declare any constants (i.e. pH=5) in advance of both problems.