Question

Proteins are long-chains of amino acids linked together. In solution, these chains tend to fold in certain ways to give the protein a structure. This folding depends on the intermolecular forces (IMFs) between water (or other molecules) and the various amino acid side-chains, as well as the IMFs between different side chains.

1.The amino acid asparagine has a melting point of 241oC whereas that of isoleucine is 295oC. Explain this difference on the basis of IMFs. HINT: it may not be what you were expecting. Consider all IMFs.

2 Would the side-chain of asparagine form favourable IMFs with water? Why or why not? Support your answer by identifying the IMFs formed between this amino acid side chain and a water molecule. Comment on the quality of these interactions and draw the strongest IMF possible between them.
 

Answer 1

1. Asparagine is an uncharged polar amino acid and interact with water forming H-bonds.on the other hand Isolucine is a hydrophobic amino acid.

The stability of proteins in its native state has an important implication on its function and evolution. The functional site analysis may lead to better understanding of how these amino acid distributions influence the melting temperature of proteins. It has been reported that increasing the fraction of hydrophobic contacts in a protein tends to raise melting temperature; increasing the fraction of repulsive charge contacts decrease the melting temperature and consistent with a destabilizing effect.

2. Yes the side-chain of asparagine does form favourable IMFs with water as the side chain contains an -OH group which can participate in H-bonding with the surrounding water molecules.