Problem:
The amino acid sequence of bovine insulin.
Required:
Question 1: Estimate the net charge of insulin at pH 9. (Hint: You can ignore the amino acid side chains that lack ionizable groups.)
Question 2: How would this number change if the disulfide bonds were reduced with mercaptoethanol?
Question 3: How accurate do you think is your result for part (a)? Explain. (Can you think of a reason why the actual charge of insulin might be different from what you calculated?)