Conformational Study of Solid Polypeptides by ¹H Combined Rotation and Multiple Pulse Spectroscopy NMR

Abstract

The relation between the 1H chemical shift and the conformation of linear homopolypeptides and cyclic dipeptides in the solid state has been studied utilizing the 1H combined rotation and multiple pulse spectroscopy (CRAMPS) NMR method. It was found that the 1H chemical shift of the Hα signal of homopolypeptides depends on the secondary structure such as α-helix or β-sheet form, whereas those of the side-chain proton signals (Hβ, Hγ, Hδ, etc.) are almost independent of the secondary structure. The 1H chemical shifts of the Hα signal of homopolypeptides having the α-helix and the β-sheet forms were 3.9−4.0 ppm and 5.1−5.5 ppm, respectively. Accordingly, the 1H chemical shift of the Hα is very useful for conformational analysis of polypeptides in the solid state. Furthermore, it is shown that the 1H chemical shift of the Hα and the NH signals of cyclic dipeptides are sensitive to the ring conformation and the hydrogen bond length in the solid state.

Amyloidosis of Alzheimer's Aβ peptides: solid‐state nuclear magnetic resonance, electron paramagnetic resonance, transmission electron microscopy, scanning transmission electron microscopy and atomic force microscopy studies

“…This -helical component gradually disappeared after 2 weeks of incubation while theˇ-strand component increased to ca 50%, indicative of complete transformation of intermediates into amyloid fibrils. 66 Indeed, solid-state 1 H MAS NMR spectra of Aˇ 1 -40 (Arc) samples incubated for 11.5 days at both pH 3.8 and 7.4 showed a sharp extra peak at ca 3.6 ppm (on a top of a broad component) previously assigned by Shoji et al 109 to the H˛signal in polypeptides having the˛-helix secondary conformation [see dominant and relatively sharp peak, manifest in these spectra at around ca 5.3 ppm, was also previously assigned to Hs ites in theˇ-strand conformations. 109 Note that these sharp peaks at 3.6 and 5.…”

“…66 Indeed, solid-state 1 H MAS NMR spectra of Aˇ 1 -40 (Arc) samples incubated for 11.5 days at both pH 3.8 and 7.4 showed a sharp extra peak at ca 3.6 ppm (on a top of a broad component) previously assigned by Shoji et al 109 to the H˛signal in polypeptides having the˛-helix secondary conformation [see dominant and relatively sharp peak, manifest in these spectra at around ca 5.3 ppm, was also previously assigned to Hs ites in theˇ-strand conformations. 109 Note that these sharp peaks at 3.6 and 5. Previously, we assigned these changes in linewidths to ordering of molecules inˇ-sheet secondary structures in fibrils.…”

Some aspects of the NMR chemical shift/structure correlation in the structural characterization of polymers and biopolymers

“…Shoji et al 71,72 showed using 1 H CRAMPS (combined rotation and multiple pulse spectroscopy) measurements on various homopolypeptides in the solid state that the 1 H chemical shifts of the H a signal of homopolypeptides with the a-helix and b-sheet forms are 3.9-4.0 p.p.m. and 5.1-5.5 p.p.m., respectively, relative to tetramethylsilane.…”

“…To obtain a high-resolution 1 H NMR spectrum for peptides and proteins in the crystalline state, there are some reports in which a combination of MAS and CRAMPS techniques is used. 71,72 However, the CRAMPS method requires a slow MAS speed for sampling the data points during acquisition (for example, the BR24 multi-pulse sequence needs less than approximately 3 kHz for sampling). The spinning rate of 3 kHz is not enough to provide a high-resolution 1 H NMR spectrum to analyze the amide proton chemical shift in peptides and polypeptides because the amide proton is directly bonded to the quadrupolar 14 N nucleus.…”

Protein structure in anisotropic environments: Development of orientational constraints

“…Such differences may be manifested in a dispersion of isotropic frequencies which represent the average of the chemical shift tensor elements and which could lead to structural constraints (40)(41)(42)(43). Shown in Fig.…”