Table 3.

Experimentally observed changes in NMR chemical shift of the G_δ imino proton (H1)

Modification type	Change in Gδ H1 chemical shift (ppm)
	Neighboring residue (Gδ)⋅Modified residue (Gα)
	9⋅3	17⋅9	11⋅15	10⋅16	3⋅21
8-BromoG	−0.26	−0.32	−0.28	−0.39	−0.28
8-OmethylG	0.22	0.24	0.40	0.39	0.30
8-AminoG	0.21	0.26	0.26	0.27	0.19

Values indicate the observed change in imino proton chemical shift of the G_δ residue as measured for single-position substitutions to syn residues. Identified by unambiguous ¹⁵N-labeling experiments, change in chemical shift is measured with respect to the spectra of the unmodified sequence.