Fig. 5

a Illusration of the small domain (green) of K223R mutant, which shows the locations of the α4 helix (blue), the loop 229–236 (purple), the loop 204–208 (purple), and the loop 220–223 (red), were displayed in cartoon by PyMOL. b RMSF values of wild-type bFMO (blue) and the K223R mutant (green). The RMSF of atomic positions was calculated according to a reference frame in the trajectory, and the RMSF of residues was calculated by averaging the RMSF of atoms of each residue. c New hydrogen bond (green dashed lines) generated between R223 with E263 and V200, respectively. R223 (purple), E263 (green) and V200 (green) were displayed as sticks. d Movement of α4 helix (blue) in the K223R mutant compared with that of the wild-type bFMO (grey). The distance of the movement was indicated by yellow dashed lines