Amide proton chemical shift

Tjandra N and Bax A 1997 Solution NMR measurement of amide proton chemical shift anisotropy in N-15-enriched proteins. Correlation with hydrogen bond length J. Am. Chem. Soc. 119 8076-82... 

The effect of a change in temperature or solvent on chemical shift is a parameter which must be carefully studied. On the basis of several examples it was proposed that evidence for hydrogen bonding (36) could be derived from the failure of an amide-proton chemical shift to be sensitive to a change in temperature. Later observations from this laboratory have shown that the chemical shift of certain amide protons not hydrogen bonded also may not be sensitive to a change in temperature. 

The above N—H bond length difference between the a-helix and /3-sheet forms seems to be related to the hydrogen bond strengths and amide proton chemical shifts. From the X-ray diffraction studies of poly(L-alanines) by... 

The i N H -NOEs can also be presented in a two-dimensional spectrum, using tbe [ N, H]-COSY-relayed i N H -NOE experiment. Positive and negative cross-peaks may then be displayed in separate subspectra (Fig. 6, B and C), which affords a nice illustration of the different dispersion of the chemical shifts in the unfolded and folded parts of the protein (Wuthrich, 1986). The spectrum of Fig. 6B is typical for a globular domain, with the backbone amide proton chemical shifts spread out from 7 to 10 ppm, and the spectrum of the tail in Fig. 6C contains backbone amide proton peaks only between 8.0 and 8.7 ppm, wbicb is typical for an extended random coil polypeptide chain. 

Tjandra N, Bax A (1997) Solution NMR measurement of amide proton chemical shift anisotropy in N-ebmiched proteins. Corrrelation with hydrogen bond length. J Am Chem Soc 119 8076-8082 Tossell JA (1984) Correlation of Si NMR chemical shifts in sihcates with orbital energy differences obtained from x-ray spectra. Phys Chem Mineral 10 137-141 Tossell JA (1992) Calculation of the Si NMR shielding tensor in forsterite. Phys Chem Mineral 19 338-342... 

Figure 1. Amide proton chemical shift changes in the trp repressor-mtr ODNA operator upon complex formation.

From the study of the pH dependence of the amide proton chemical shifts, Wuthrich and Wagner (1979) were able to conclude that the titration shifts result from long-range interactions with the ionizable groups of the protein, and therefore they are mainly dependent on the protein conformation. 

---