Table 2.

Sum of the relative energies of the four 5′-GpG-3′dinucleotides of the 2-quartet G-DNA stems evaluated as gas phase single points (kcal/mol).^a>

Method/ Stem	AA	SA-aabb	SA- abab	SA-abab-2	SA- aaab	3AA+1S S	AS	SA-aaaa
QMoptb	0	+16.6 (+26.6)	+28.7	+4.6 (+14.6)	+19.1	+17.0	−6.3	−18.7 (+21.3)
QM→MMoptc	0	−9.9 (+5.3)	+5.7	−25.1 (−15.6)	−5.0	+17.9	−12.4	−60.3 (+1.0)
Differenced	0	−26.5 (−21.3)	−23.0	−29.7 (−30.2)	−24.1	+0.9	−6.1	−41.6 (−20.3)
T2-T1e		+0.9 (+6.4)	+1.6	−2.8 (−2.0)	+2.7	+5.6	+13.3	−9.2 (+7.1)

^aFor energies of all the individual GpG dinucleotides, see Supporting InformationTable S2. The values in parentheses are without the 5′ terminal O5′H…N3(G) H-bonds (cf. Table 1).

^bOptimization using the DFT-D3 COSMO approach starting from the initial structure.

^cOptimization using the parmbsc0 force field and PB method starting from the QM_opt structure.

^dDifference between MM and QM relative energies. The estimates in parentheses were obtained when considering the deductions of the energies of the terminal O5′H…N3(G) H-bonds.

^eDifference between predictions from Tables 2 and 1 (lines “Difference”).