. 2011 Oct 19;101(8):1987–1998. doi: 10.1016/j.bpj.2011.08.049

Table 5.

Computed effects of guanine substitutions on the N1-H1⋅⋅⋅O6 geometry of the tetrad

Modification type	Optimization basis set	Computed change in H1⋅⋅⋅O6 length (pm)				Computed change in N1–H1⋅⋅⋅O6 Angle (°)
Modification type	Optimization basis set	G_α⋅G_β	G_β⋅G_γ	G_γ⋅G_δ	G_δ⋅G_α	G_α⋅G_β	G_β⋅G_γ	G_γ⋅G_δ	G_δ⋅G_α
8-BromoG	6-31G(d)	−0.97	0.99	1.57	5.02	−1.12	−0.12	0.00	−1.51
	6-31G(d,p)	−0.96	0.97	1.52	4.92	−1.07	−0.11	0.00	−1.45
	6-31++G(d,p)	−1.05	0.44	0.66	2.96	−0.60	0.00	−0.01	−0.69
	6-311++G(d,p)	−0.50	0.18	0.63	1.80	−0.11	0.08	−0.08	−0.18
8−OmethylG	6-31G(d)	1.08	−1.97	−2.11	−10.14	3.80	0.46	−0.22	3.35
	6-31G(d,p)	1.00	−1.98	−2.11	−10.10	3.77	0.45	−0.22	3.31
	6-31++G(d,p)	1.13	−2.10	−2.11	−10.26	3.89	0.47	−0.21	3.41
	6-311++G(d,p)	0.92	−2.44	−2.23	−11.02	4.07	0.56	−0.18	3.60
8-AminoG	6-31G(d)	−0.15	−1.06	−2.49	−6.25	2.15	0.21	0.19	1.60
	6-31G(d,p)	−0.14	−1.08	−2.50	−6.30	2.12	0.21	0.18	1.60
	6-31++G(d,p)	−0.08	−1.18	−2.51	−6.51	2.21	0.23	0.18	1.71
	6-311++G(d,p)	−0.35	−1.36	−2.70	−6.83	2.30	0.29	0.24	1.79

Geometry changes listed reflect deviations from the original values of bond length and angle as found in the unmodified optimized structures. Unmodified tetrad N1-H1⋅⋅⋅O6 hydrogen-bond geometries obtained are 6-31G(d), 214.33 pm and 157.04°; 6-31G(d,p), 214.07 pm and 157.18°; 6-31++G(d,p), 215.08 pm and 157.76°; and 6-311++G(d,p), 216.27 pm and 157.14°. Listed angles were measured toward the center of the tetrad. Variations of 2.20 pm and 0.72° were observed for hydrogen-bond length and angle, respectively, in the optimized geometries of unmodified tetrads across the basis sets explored.