. Author manuscript; available in PMC: 2015 Jun 15.

Published in final edited form as: J Comput Chem. 2014 Apr 18;35(16):1219–1239. doi: 10.1002/jcc.23611

Table 2.

Relative Energies of the Conformations of the Nucleosides of Adenine and Cytosine (Model Compounds 3 and 4) Sampled in Canonical A and B forms DNA ^a

Level of theory	A form: north sugar, χ = 200°		B form: south sugar, χ = 240°
Level of theory	phase angle	ΔE	phase angle	ΔE

NUSA

QM	9.35	−0.21	173.85	0.00
Drude	9.31	−0.75	173.81	0.00
C36	9.26	−1.26	172.96	0.00

NUSC

QM	12.65	−2.05	167.00	0.00
Drude	12.68	−2.92	166.94	0.00
C36	12.75	−4.52	166.53	0.00

Values presented for conformations 2 (A form) and 5 (B form) in Fig. 7. Energies in kcal/mol and angles in degrees. Sugar pucker phase angle calculated on the basis of the method of Altona and Sundaralingam¹⁰⁴ with QM data at the RIMP2/cc-pVTZ//MP2/6–31(+)G(d) level. β, γ and ε dihedral angles, and two of the five sugar torsions, ν₀ and ν₄, were restrained to the values corresponding to either A or B forms DNA. See Methods section.