Question

Please help explain the reagents and what they do, explain the reasoning behind the answers please, not simply the answer. I don't understand why the answers are what they are.:

The following reagents are often used in protein chemistry: CNBr, Urea, Mercaptoethanol, Chymotrypsin, Trypsin, Performic acid, 6N HCl, Pheyl isothiocyanate

Which one is the best suited for accomplishing each of the following tasks?

a) Determination of the amino acid sequence of a small peptide

b) Reversible denaturation of a protein devoid of disulfide bonds. Which additional reagent would you need if disulfide bonds were present?

c) Hydrolysis of peptide bonds on the carboxyl side of aromatic residues

d) Cleavage of peptide bonds on the carboxyl side of methionines

e) Hydrolysis of peptide bonds on the carboxyl side of lysine and arginine residues

Again, I know the answers are:

a) phenyl isothiocyanate b) urea and β-mercaptoethanol to reduce disulfides c) chymotrypsin d) CNBr e) trypsin

However, I have no idea why they are the correct answers. Thank you.