Table 4. Accuracy of MM Energy Estimates with Different Torsion Parameters^a.

	force field accuracy			term count		torsion energy sum
system	V-ff14b	V-ff99c	V-ff14ntd	V-ff14	V-ff99	V-ff14	V-ff99
Arg	0.92	1.20	2.19	63	35	31.53	13.65
Ash	1.01	1.38	3.69	53	31	27.25	16.77
Asn	0.80	1.35	1.99	53	28	8.12	17.95
Asp	1.74	3.44	3.61	41	28	14.70	11.57
Cys	0.99	1.24	2.23	43	29	16.50	12.09
Cyx	1.22	1.48	1.94	38	28	19.43	10.93
Glh	0.80	0.99	2.16	60	33	29.16	14.44
Gln	0.67	0.86	2.00	60	30	20.40	18.33
Glu	1.27	1.80	2.04	48	30	16.97	12.32
Hid	0.79	0.99	1.93	52	34	25.44	11.75
Hie	0.78	1.03	1.87	52	34	23.26	11.72
Hip	1.50	1.63	2.63	51	33	24.28	11.78
Ile	0.64	1.14	2.28	63	33	24.46	13.25
Leu	0.77	0.99	2.01	48	33	18.87	13.75
Lys	1.20	1.57	2.73	56	34	17.28	14.43
Met	0.79	0.96	2.13	49	29	15.65	12.86
Phe	0.75	0.99	1.90	42	30	25.54	11.80
Ser	0.81	1.00	1.97	45	33	24.83	12.15
Thr	0.89	1.35	2.75	61	36	75.76	13.28
Trp	0.79	1.12	2.40	55	37	40.57	12.03
Tyr	0.79	0.90	1.95	45	32	24.48	13.09
Val	0.63	0.81	1.65	41	30	24.43	11.97
Ala3	1.14	1.23	1.99	30	28	61.62	25.03
Gly3	0.96	1.17	1.85	21	19	43.20	23.71

^aIn all cases, the charge set Q^vac fitted to reproduce the electrostatic potentials of blocked dipeptides in vacuo was used to estimate the molecular mechanics energy of each blocked dipeptide in vacuum. All energies are given in kcal/mol.

^bThe V-ff14 force field: Q^vac has been substituted for the implicitly polarized charge set in the release version.

^cThe ff99 force field, with Q^vac as derived for V-ff14 (identical to the force field in the first column, but with a smaller torsion parameter space).

^dV-ff14 with no torsion Fourier series terms.