TfCut, the correlation takes place between the tryptophan (W190 and W195 respectively) in loop W, and A213 and A219, respectively. It is therefore possible that both the enhanced fluctuations of loops H and D, as well as the decreased correlations of the dynamics of the conserved tryptophan in loop W with residues on loop D, may depend on the bulkier nature of histidine and phenylalanine, which may exert additional steric repulsion on loop W.