The following proteins represent a wide range of molecular weights and isoelectricpoints. Mr is the molecular weight of a single protein chain. • Protein 1: Mr 68,544; pI 6.11 (monomer) • Protein 2: Mr 29,041; pI 5.32 (dimer) • Protein 3: Mr 15,805; pI 5.7 (dimer) • Protein 4: Mr 12,165; pI 4.74 a. Which protein is the most acidic? Explain your answer. b. Which protein will migrate the slowest in an SDS-PAGE? Explain your answer. c. In what order will these proteins elute from a cation exchanger at pH 8? Explain your answer. d. In what order will these proteins salt out from a pH 7 solution by the dropwise addition of saturated ammonium sulfate? Explain your answer.