The Effects of Quantum Tunneling on the Conformational Entropy of the Cas9 Protein

The Cas9 protein is a protein that is used in bacteria to edit out viral DNA. Cas9 is very precise and is used in laboratories all over the world for the purposes of editing gene sequences. In order for Cas9 to function properly it needs to fold into a specific shape. These shapes are referred to as conformations and the entropy corresponding to the number of conformations that a polymer chain can fold into is referred to as the conformational entropy. Until recently, the current model used for calculating the conformational entropy failed to incorporate the effects due to hydrogen bonds. Now a research group from Chicago has constructed a model that incorporates these effects. It has been demonstrated that the effects due to quantum interactions without tunneling effects influence the conformational entropy by an order of magnitude of 0.7% for backbone interactions and 10% for sidechain interactions respectively. The effects due to tunneling further influence the backbone entropy by an order of magnitude of 0.08%.