Table 1. Revised Torsion Parameters Obtained from a Fit to Torsion Energy Profiles Calculated at the MP2 Level of Theorya.
| angle | ϕ1 | k1 | ϕ2 | k2 | ϕ3 | k3 | ϕ4 | k4 |
|---|---|---|---|---|---|---|---|---|
| χA | –7.75 | –0.5250 | –4.44 | 1.9578 | –35.39 | –0.9569 | –21.36 | 0.2058 |
| χC | 138.56 | –1.0002 | –31.94 | 2.8162 | 34.57 | –1.1862 | –53.36 | 0.7164 |
| χT | –7.14 | –0.1027 | –2.45 | 2.2160 | –13.96 | –0.9599 | –123.92 | –0.2482 |
| χG | 6.19 | –0.5093 | –0.54 | 1.7381 | –29.00 | –0.8156 | –2.69 | 0.2408 |
| ζ | –154.60 | –0.2379 | –4.09 | 1.6200 | –51.37 | 0.4252 |
a
Torsion angle potentials, Vϕ, are expressed as 
. The
χ torsion angle parameters were
made nucleotide-specific (subscripts A, C, T, and G), while the same
set of ζ torsion angle parameters was used for all nucleotides.
Units are degrees for angles and kcal mol–1 for
force constants.