FK506 binding protein (FKBP) in a complex with dimethyl sulfoxide (DMSO), methyl methylsulfinylmethyl sulfide (DSS), or 4-hydroxy-2-butanone (BUT) was obtained from PDB ID 1D7H, 1D7I, and 1D7J, respectively . The FKBP-DMSO system is shown in Figure . Amber ff99SB-ILDN was used for the protein; GAFF2 was used for the DMSO, DSS, and BUT molecules, whose partial atomic charges were calculated by the semi-empirical method: AM1-BCC . Further, CHARMM22 with CMAP was used for FKBP, and SwissParam 45 was used for DMSO, DSS, and BUT.