Outline the steps to estimate the net charge of a peptide at pH 7.4 with the following ionizable groups: N-terminus (pKa 9.0), lysine side chain (pKa 10.5), and C-terminus (pKa 3.0).

• A. Compare pKa to pH, determine charge, identify ionizable groups, and sum charges.
• B. Identify ionizable groups, sum charges, compare pKa to pH, and determine charge.
• C. Identify ionizable groups, compare pKa to pH, determine charge, and sum charges.
• D. Sum charges, identify ionizable groups, compare pKa to pH, and determine charge.

Answer: (C)