The key catalytic amino acids of the chymotrypsin active site in the free enzyme are: A. a serine, an aspartic acid with a deprotonated side chain and a histidine with a protonated side chain. B. a serine, an aspartic acid with a deprotonated side chain and a histidine with a deprotonated side chain. C. a serine, an aspartic acid with a protonated side chain and a histidine with a protonated side chain. D. a serine, an aspartic acid with a protonated side chain and a histidine with a deprotonated side chain. E. a serine, an aspartic acid, and a histidine; each of which has a deprotonated side chain.

Achemist at a pharmaceutical company is measuring equilibrium constants for reactions in which drug candidate molecules bind to a protein involved in cancer. the drug molecules bind the protein in a 1: 1 ratio to form a drug-protein complex. the protein concentration in aqueous solution at 25 ˚c is 1.74 x10-6 m . drug a is introduced into the protein solution at an initial concentration of 2.00 x10-6m. drug b is introduced into a separate, identical protein solution at an initial concentration of 2.00 x10-6m. at equilibrium, the drug a-protein solution has an a-protein complex concentration of 1.00 x10-6m, and the drug b solution has a b-protein complex concentration of 1.40 x10-6m.a. calculate the kc value for the a-protein binding reaction.b. calculate the kc value for the b-protein binding reaction.c. assuming that the drug that binds more strongly will be more effective, which drug is the better choice for further research?