Table 1 Energetic characteristics (in kcal∙mol−1) of the discovered conformational transitions of the four biologically important А·Т DNA bps obtained at the MP2/aug-cc-pVDZ//B3LYP/6-311++G(d,p) level of theory in the continuum with ε = 4 (see Fig. 1).

From: Non-dissociative structural transitions of the Watson-Crick and reverse Watson-Crick А·Т DNA base pairs into the Hoogsteen and reverse Hoogsteen forms

Conformational transition

νia

∆Gb

∆Ec

∆∆GTSd

∆∆ETSe

∆∆Gf

∆∆Eg

А·Т(wWC)R,L ↔ А·Т(wН)R,L

7.7

−0.01

−0.19

1.97

0.08

1.98

0.28

А·Т(wWC)R,L \(\mathop{\longleftrightarrow }\limits^{cys}\) А·Т(wН)L,R

250.9

−0.01

−0.19

9.53

9.00

9.54

9.19

А·Т(wrWC)R,L \(\mathop{\longleftrightarrow }\limits^{trans}\) А·Т(wrН)L,R

252.7

−0.01

−0.19

9.52

9.15

9.53

9.34

А·Т(wrWC)R,L ↔ А·Т(wrН)R,L

16.1

−0.18

−0.24

1.84

0.41

2.02

0.64

А·Т(wrWC)R,L \(\mathop{\longleftrightarrow }\limits^{cys}\) А·Т(wrН)L,R

252.3

−0.18

−0.24

9.12

8.86

9.30

9.09

А·Т(wrWC)R,L \(\mathop{\longleftrightarrow }\limits^{trans}\) А·Т(wrН)L,R

253.7

−0.18

−0.24

9.28

9.24

9.46

9.48

  1. aImaginary frequency at the TS of the conformational transition, cm−1. bThe Gibbs free energy of the product relatively the reactant of the conformational transition (T = 298.15 K). cThe electronic energy of the product relatively the reactant of the conformational transition. dThe Gibbs free energy barrier for the forward conformational transition. eThe electronic energy barrier for the forward conformational transition. fThe Gibbs free energy barrier for the reverse conformational transition. gThe electronic energy barrier for the reverse conformational transition.
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