The potential destabilizing effects on the VWF A1 domain caused by the M1304R mutation. (A) Location of Met1304 in the crystal structure of the wild-type A1. The side chain of Met1304 is surrounded by hydrophobic residues in the wild-type VWF A1 structure. (B) Flexibility of the mutant (M1304R) and wild-type A1 structures in MD simulations. Root-mean-square fluctuations (RMSF) of Cα atoms averaged over the last 40 ns of the simulations (total 50 ns) are shown. The Cα of the mutant A1 (magenta-solid line) in the simulations fluctuate more around the mean than Cα of wild-type A1 (black dashed line). The shaded area indicates the residues at or around the mutation site. (C) Time course of backbone deviation of the α-helix that contains residue 1304. RMSDs were monitored over time for the backbone of the α-helix comprising residues 1290 to 1305; mutant (magenta), wild-type (black). The mutant structure deviated more from the initial structure than did the wild-type, represented by increased CαRMSD.