Revealing the specific solute–solvent interactions via the measurements of the NMR spin–spin coupling constants

Revisiting the influence of pH on 1 J C α H and chemical shifts of glycine and alanine short oligopeptides

“…Figure 3 shows the titration curves of 1 H and 13 C chemical shifts of CH 2 group for all three glycine residues in triglycine. The actual pH of the solution, denoted as pD, was corrected as explained in Material and methods.…”

“…Oligopeptides with natural abundance of 13 C and 15 N were mostly purchased from Sigma Aldrich. D 2 O and enriched glycine (2-13 C, 99%; 15 N, 98%+) were purchased from Cambridge Isotope Laboratories.…”

“…A large set of 1 H, 13 C{ 1 H} and 13 C spectra were recorded and 1 H, 13 C chemical shifts and 1 J CH spinspin coupling constants were obtained. The 1 J CαH couplings were determined from 13 C satellite lines in 1 H spectra and/or from 13 C non-decoupled spectra.…”

“…It is known that NMR parameters are highly sensitive to external and internal electric fields [10][11][12][13]. The electrostatic effects on the CC, CH, CR and CN bonds of amino acids depend on the ionic state and are significantly different, which should be reflected in corresponding NMR parameters and allow differentiation of the ionic state of amino acid.…”

“…Figure 6. Linear dependence of 1 J CαH from13 C chemical shifts of CH 2 groups of glycine residues in GGG: GGG (blue diamonds), GGG (red triangles), GGG (green circles).…”