Table 1.
Residue | Small molecule | ΔGexp | ΔGDelPhi | ΔGMTK | ΔGerror |
---|---|---|---|---|---|
Arg+ | N-propyl guanidinium | – | −66.07 | −64.49 | – |
Lys+ | N-butyl ammonium | −69.24 | −69.44 | −69.11 | 0.13 |
His+ | Methyl imidazolium | −64.13 | −64.36 | −64.81 | −0.68 |
His0 | Methyl imidazole | −10.25 | −10.22 | −9.32 | 0.93 |
Asp− | Acetate | −80.65 | −80.44 | −79.05 | 1.60 |
Asp0 | Acetic acid | −6.70 | −6.63 | −5.57 | 1.13 |
Asn | Acetamide | −9.72 | −9.76 | −8.85 | 0.87 |
Glu− | Propionate | −79.12 | −79.21 | −77.53 | 1.59 |
Glu0 | Propionic acid | −6.47 | −6.41 | −5.25 | 1.22 |
Gln | Propionamide | −9.42 | −9.42 | −8.55 | 0.87 |
Cys− | Methylthiol ion | −76.79 | −76.66 | −75.85 | 0.94 |
Cys0 | Methylthiol | −1.24 | −1.35 | −1.08 | 0.16 |
Tyr− | p-cresol ion | −75.01 | −74.88 | −71.90 | 3.11 |
Tyr0 | p-cresol | −6.13 | −6.11 | −4.74 | 1.39 |
Ser | Methanol | −5.08 | −5.44 | −4.83 | 0.25 |
Thr | Ethanol | −4.90 | −5.02 | −4.55 | 0.35 |
Met | Methylethyl sulfide | −1.49 | −1.46 | −1.07 | 0.42 |
Trp | Methyl indole | −5.91 | −5.84 | −4.76 | 1.15 |
Phe | Toluene | −0.76 | −0.77 | −0.37 | 0.39 |
BB | N-methyl acetamide | −10.08 | −10.00 | −9.53 | 0.55 |
Shown are experimental and calculated vacuum (ɛp = 2, ɛs = 1) to water (ɛp = 2, ɛs = 80) transfer free energies (kcal/mol) for small-molecule analogs of the amino-acid side chains. ΔGexp indicates the experimental transfer free energy. ΔGDelPhi indicates the transfer free energy reported by Sitkoff et al. (27) using the DelPhi program (29). ΔGMTK and ΔGerror indicate the MTK transfer free energy and its error with respect to the experimentally measured value.