Question

9. Aromatic residues, such as tyrosine, phenylalanine, and tryptophan, are common in a polypeptide. Their side chains have an aromatic ring, which is a resonant structure composed of TT bonds. When a cation in the solution is closed to this aromatic structure, it can polarize the ring to form a dipole. Will this cation- aromatic ring interaction be stable in water or non-polar solvent? Briefly explain why. (10 pts)

Answer 1

All three residue have aromatic rings and have polar atoms in its structure, definately it will soluble in water over the hexane when metal ion present in the enviorement or in close affinity to their structure. Because in non-polar condition like in hexane the amino-acids prefers to be attain their native state, while in aq. enviorement amino acids prefers to stay in zwitter-ionicform and metal ions preferably interact with zwitter ionic over the native structure of amino-acids.

Moreover by Theoratical and experimental conditional it was seen that all the above mentioned residue interact better and more stable when they interact with Metals 2+ ions in solution. Phenylalanine, tyrosine and tryptophan complexes with Ni2+ and Cu2+ the most stable structure when they are in aqueous conditions.