The following points highlight the top two bonds relating to protein structure. The bonds are: 1. Strong Bonds 2. Weak Bonds.
Protein Structure: Bond # 1. Strong Bonds:
A. Peptide bonds:
The primary structure of proteins is derived from peptide bonds which can be established by the following evidences:
i. Proteases produce polypeptides by hydrolyzing proteins. They can also hydrolyze peptide bonds.
ii. The protein, insulin, is synthesized by linking amino-acids by peptide bonds.
iii. Polypeptides, like proteins, react with biuret reagent which is suggestive of 2 or more peptide bonds.
B. Disulphide bond:
i. The disulphide bond may interconnect two parallel chains through cysteine within each polypeptide shown in the Fig. 6.1.
ii. The bond is not broken under the usual conditions of denaturation.
iii. Per-formic acid is used to oxidize insulin to separate the protein molecule into its constituent polypeptide chains without affecting the other part of the molecule.
Protein Structure: Bond # 2. Weak Bonds:
A. Hydrogen bonds:
i. The hydrogen bond appears from the sharing of hydrogen atoms between the nitrogen and the carbonyl oxygen of different peptide bonds as shown below by star mark.
ii. Each hydrogen bond is quite weak.
iii. During denaturation of a protein, the hydrogen and hydrophobic bonds are broken.
B. Hydrophobic bonds:
i. The nonpolar side chains of neutral amino acids are closely associated with one another in proteins.
ii. No true bond exists.
iii. Nonetheless, they play an important role in maintaining protein structure.