Dear All,

 

Suppose the protein crystal resolution is about 2-3A, then in the map it should be rather difficult to distinguish the C and N in the sidechain of HIS. In this way we may regard the sidechain of HIS is flippable. But suppose in one flipped conformation of the HIS, the free N in the sidechain of HIS can form H-bond with the neighbour H of the OH of the Thr, in the other flipped conformation of the HIS, the free N in the sidechain of HIS cannot form H-bond with the neighbour H of the OH of the Thr (caused by distance issue).

 

Suppose whether the H-bond forms between the free N in the sidechain of HIS and the neighbour H of the OH of the Thr was very important biologically, in this situation how can we distinguish whether the H-bond forms?

 

Smith