Determination of accurate 1H positions of an alanine tripeptide with anti-parallel and parallel β-sheet structures by high resolution 1H solid state NMR and GIPAW chemical shift calculation

Abstract

The accurate (1)H positions of alanine tripeptide, A(3), with anti-parallel and parallel β-sheet structures could be determined by highly resolved (1)H DQMAS solid-state NMR spectra and (1)H chemical shift calculation with gauge-including projector augmented wave calculations.

Difference in the structures of alanine tri‐ and tetra‐peptides with antiparallel β‐sheet assessed by X‐ray diffraction, solid‐state NMR and chemical shift calculations by GIPAW

“…13 C, and (c) 15 N. (X-ray: calculated based on single crystal X-ray structure and Opt: 1 H geometry optimized structure). 13 C, and (c) 15 N. (X-ray: calculated based on single crystal X-ray structure and Opt: 1 H geometry optimized structure).…”

“…The DQMAS spectrum of AP-Ala 4 clearly shows that the diagonal peak at 9.0 ppm and off-diagonal shoulder peak around 8.6 ppm in the SQ domain originate from NH 3 and NH protons, respectively (see the projection in Figure 4b). [15][16][17] The H N chemical shits for Ala 4 (9.1, 8.8, and 8.7 ppm) are slightly lower than Ala 3 (8.6 and 8.3 ppm). A strong cross peak of H a at 4.6 ppm in SQ domain with the NH 3 peak at 4.6 1 9.0 5 13.6 ppm in DQ domain indicates that the peak at 4.6 ppm is the H a in the same residue, 1-H a .…”

“…Further assignments were carried out through cross peaks between H N and H a regions. 15 This result indicates that closer and stronger Interestingly, two diagonal peaks appeared in the H a region around 4.5 and 5.2 ppm in the SQ domain.…”

“…Specificcialy, the b-sheet structure of Ala 3 is a heterogeneous mixture, but of Ala 4 is uniform in composition and thus the Ala 4 structure is simpler than Ala 3 . Moreover, 15 N CP/ MAS NMR spectra demonstrate that Ala 3 gives the spectral lines composed of two sets of two amide groups 15 N and one ammonium group 15 N, 14 whereas Ala 4 gives one set of three amide groups 15 N and one ammonium group 15 N. Only the 15 N chemical shift data are listed in Table I. The C a spectrum of AP-Ala 4 is composed of four peaks in a narrower range of 47-50 ppm, whereas that of AP-Ala 3 is complex and largely dispersed over 8 ppm.…”

3D 14N/1H Double Quantum/1H Single Quantum Correlation Solid‐State NMR for Probing the Parallel and Anti‐Parallel Beta‐Sheet Arrangement of Oligo‐Peptides at Natural Abundance

“…This method revealed that the interstrand NH/NH correlations are only observed in AP‐structure. However, the measurement of 14 N/ 14 N correlation caused low sensitivity due to two 1 H/ 14 N HMQC filterings and the overlap of NH/NH correlations on the diagonal peaks in 2D spectra ,,. The limitations obscured the observation of NH/NH correlations and required a long measurement time.…”