The image below plots the denaturation of ribonuclease A as

The image below plots the denaturation of ribonuclease A as a function of guanidine hydrochloride (GdnHCl, structure shown at the right of the plot) concentration, monitored by circular dichroism. Explain this curve in biochemical terms (what is happening to the structure of the protein and why?). Comment about the cooperative nature of this process.

Solution

The graph is showing that the ribonuclease is getting denatured by guanidine hydrochloride which is leading to a negative rotation but not to that extent as observed with urea denaturation. This leads to a randomly coiled conformation.

With the assumption of a 2 state mechanism, an apparent free energy of unfolding is changing almost linearly with the increasing concentration of denaturant.Guanidine hydrochloride is highly effective in unfolding ribonuclease because of the buried polypeptide chain of ribonuclease A is highly polar.