Chapter 17, Problem 55P

(a)

Interpretation Introduction

Interpretation:

The fragments obtained from the cleavage of given peptide chain by trypsin, cyanogen bromide and chymotrypsin should be given.

Concept introduction:

Amino acids are linked each other by peptide bonds is called protein (one or more peptide bonds). Peptide bonds are amide bonds, in which carbonyl group of one amino acid bonded to amino group of other amino acid. The chain of the protein is drawn in such a way that left end is occupied by free amino group (say N-terminal) and right side of the chain is occupied by carbonyl group (say C-terminal).

Endopeptidases cleave peptide bonds that are not at the end.

Trypsin is an endopeptidase, which cleave the C-side peptide bond of positively charged side chains such as arginine and lysine.

Chymotrypsin is an endopeptidase, which cleave the C-side peptide bond of amino acids that contain aromatic six-membered rings such as Phe, Tyr and Trp.

Cyanogen bromide cleaves the C-terminal peptide of Methionine in a peptide chain.

(b)

Interpretation Introduction

Interpretation:

The numbers of primary structure if the amino acids contained in each fragment are known has to be determined.

Concept introduction:

The number of primary structures in a polypeptide is determined by checking the number of disulfide bridges connected with primary structures. 

Disulfide bridges are formed between thiol groups of cysteine.