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

Abstract

Alanine oligomers provide a key structure for silk fibers from spider and wild silkworms.We report on structural analysis of L-alanyl-L-alanyl-L-alanyl-L-alanine (Ala)4 with anti-parallel (AP) β-structures using X-ray and solid-state NMR. All of the Ala residues in the (Ala)4 are in equivalent positions, whereas for alanine trimer (Ala)3 there are two alternative locations in a unit cell as reported previously (Fawcett and Camerman, Acta Cryst., 1975, 31, 658-665). (Ala)4 with AP β-structure is more stable than AP-(Ala)3 due to formation of the stronger hydrogen bonds. The intermolecular structure of (Ala)4 is also different from polyalanine fiber structure, indicating that the interchain arrangement of AP β-structure changes with increasing alanine sequencelength. Furthermore the precise (1)H positions, which are usually inaccesible by X-ray diffraction method, are determined by high resolution (1)H solid state NMR combined with the chemical shift calculations by the gauge-including projector augmented wave method.

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

“…Figure (C) and (D) show 1D 1 H spectra of P‐ and AP‐Ala 3 including three 1 H peaks of CH 3 , CH, and NH/NH 3 + . The detailed assignment of 1 H chemical shift of P‐ and AP‐Ala 3 and the structural information were reported in the previous study ,. Here, the protons of CH 3 , CH, NH, and NH 3 + refer to 1 H β , 1 H α , 1 H NH , and 1 H NH3 + .…”

Towards a Supertough Thermoplastic Polyisoprene Elastomer Based on a Biomimic Strategy

“…It is found that there are multi diffraction peaks in the spectra. The diffraction peaks with d spacing of 3.01–3.04 Å were detected in both oligopeptide‐decorated samples, which should be assigned to the hydrogen spacing in a β‐sheet structure . Typically, the disordered structures will induce the augment of hydrogen bonds spacing .…”

Towards a Supertough Thermoplastic Polyisoprene Elastomer Based on a Biomimic Strategy

“…As acomparison, randomly functionalized polyisoprene (R-OH-PIP) without at erminal polar block was also prepared by tuning the feeding sequence of monomers (Scheme 1). [28] Typically,t he disordered structures will induce the augment of hydrogen bonds spacing. Themolecular weights of two samples are high enough to ensure the mechanical properties.…”

“…[28] Typically,t he disordered structures will induce the augment of hydrogen bonds spacing. [28] Typically,t he disordered structures will induce the augment of hydrogen bonds spacing.…”

“…The sample was loaded to the strain at 5.0 in each cycle.Figure 2. a) Crystallinity index (CI) as afunction of strain and b) WAXD patterns of B-OH-PIP, B-4A-PIP, R-OH-PIP,a nd R-4A-PIP.peptide-decorated samples,w hich should be assigned to the hydrogen spacing in a b-sheet structure. [28] Typically,t he disordered structures will induce the augment of hydrogen bonds spacing. [29] Hence,asecond reflection around aspacing of 3.13 were attributed to the hydrogen spacing in extended chain structures.A nd the reflections at as pacing of 3.56 and 3.36 should be ascribed to the hydrogen spacing in random coils.Compared to R-4A-PIP,the diffraction peaks of B-4A-PIP assigned to b-sheet and extended chain structures were sharper, and those assigned to random coils were smaller.…”