. Author manuscript; available in PMC: 2014 Dec 10.

Published in final edited form as: J Chem Theory Comput. 2013 Dec 10;9(12):5430–5449. doi: 10.1021/ct400781b

Table 4.

Target data for Monte Carlo Simulated Annealing optimization of the polypeptide backbone electrostatic parameters along with the values from the final Drude-3 model.

Relative energies of Acetyl-(Ala)₅-amide
	RIMP2/cc-pVDZ	RIMP2/cc-pVTZ//RIMP2/cc-pVDZ	Drude-3
alphaR – C5	−10.39	−6.59	−3.89
alphaR – PPII	−16.63	−14.83	−10.17

Water interactions with alanine dipeptide.^a
	C5				PPII
	Int. Energy		Distance		Int. Energy		Distance
	QM	Drude-3	QM	Drude-3	QM	Drude-3	QM	Drude-3
OY-LP	−6.48	−6.35	1.89	1.89	−6.07	−5.78	1.90	1.91
O-LP	−5.60	−5.13	1.93	1.95	−6.13	−5.54	1.91	1.94
OY-straight	−5.50	−5.71	1.93	1.95	−5.80	−5.24	1.92	1.95
O-straight	−4.71	−4.75	1.94	1.95	−5.26	−5.08	1.93	1.95
HN	0.50	0.40	3.01	3.00	−5.15	−5.90	1.96	1.92
HNT	−5.68	−6.18	2.03	1.99	−5.76	−6.40	1.97	1.91

Molecular dipole moment of the alanine dipeptide (Debye)^b
	αR		C5		PPII		C7eq
	QM	Drude-3	QM	Drude-3	QM	Drude-3	QM	Drude-3
μ	6.23	6.67	4.66	2.63	4.17	3.59	2.32	3.77
μ_x	1.32	3.02	−4.40	−2.27	−0.93	0.82	2.29	3.62
μ_y	−1.62	−1.48	−1.01	−0.28	−3.67	−3.33	−0.27	−0.70
μ_z	5.87	5.76	1.18	1.31	−1.74	−1.09	0.30	0.78

Molecular polarizability of alanine dipeptide (Å³)
	αR		C5		PPII		C7eq
	QM	Drude-3	QM	Drude-3	QM	Drude-3	QM	Drude-3
α _{x x}	13.57	15.30	15.49	16.07	14.79	16.39	14.06	15.47
α _{y y}	12.72	14.36	12.06	13.88	12.25	13.88	13.92	14.69
α _{z z}	11.71	9.94	10.35	10.39	11.01	8.45	10.40	9.72

Energies in kcal/mol and distances in Å. a) Water interactions correspond to the minimum interaction energy distances with rigid monomer geometries with the QM data obtained using MP2/aug-cc-pVDZ optimizations followed by single point energies at the MP2/cc-pVQZ model chemistry. b) QM dipole moments and polarizabilities obtained at the B3LYP/aug-cc-pVDZ level with the polarizabilities scaled by 0.85 prior to fitting.