Untitled

Abstract

Spiders synthesize several kinds of silk fibers. In the primary structure of spider silk, one of the major ampullate (dragline, frame) silks, spidroin 1, and flagelliform silk (core fibers of adhesive spiral), there are common repeated X-Gly-Gly (X = Ala, Leu, Pro, Tyr, Glu, and Arg) sequences, which are considered to be related to the elastic character of these fibers. In this paper, two dimensional spin diffusion solid-state NMR under off magic angle spinning (OMAS), (13)C chemical shift contour plots, and Rotational Echo DOuble Resonance (REDOR) were applied to determine the torsion angles of one Ala and two kinds of Gly residues in the Ala-Gly-Gly sequence of (13)C=O isotope-labeled (Ala-Gly-Gly)(10). The torsion angles were determined to be (phi, psi) = (-90 degrees, 150 degrees ) within an experimental error of +/-10 degrees for each residue. This conformation is characterized as 3(1) helix which is in agreement with the structure proposed from the X-ray powder diffraction pattern of poly(Ala-Gly-Gly). The 3(1) helix of (Ala-Gly-Gly)(10) does not change by formic acid treatment although (Ala-Gly)(15) easily changes from the silk I conformation (the structure of Bombyx mori silk fibroin before spinning in the solid state) to silk II conformation (the structure of the silk fiber after spinning) by such treatment. Thus, the 3(1) helix conformation of (Ala-Gly-Gly)(10) is considered very stable. Furthermore, the torsion angles of the 16th Leu residue of (Leu-Gly-Gly)(10) were also determined as (phi, psi) = (-90 degrees, 150 degrees ) and this peptide is also considered to take 3(1) helix conformation.

Structure of Characteristic Sequences in Nephila clavipes Dragline Silk (MaSp1) Studied with 13C Solid State NMR

“…However, the chemical shift value corresponds to both -sheet and 3 1 helix conformations 22 and therefore we cannot distinguish the conformation although it is different from either -helix (52.5 ppm) or random coil (50.0 ppm) ( Table I). The C=O chemical shift at the Gly 27th position in the sequence, LGSQ, is 171.5 ppm (the spectrum is not shown here), which is close to the value of both 3 1 helix and random coil, 171.3 ppm.…”

Conformational Characterization of (Val-Pro-Gly-Val-Gly)6 with 13C Solid State NMR

“…The mixing time of 2 s was optimized for spin diffusion between intramolecular specific carbon atoms of selectively isotope-labeled Val and Gly residues; however, for no spin-diffusion between intermolecular carbon atoms. [5][6][7] The contact time was set to 2 ms using the Variable-Amplitude CP technique. 8 About 400 scans with a number of t 1 points of 150 and a recy-cle delay of 2 s were accumulated for every 2D experiment.…”

“…demonstrate the difference between the observed and calculated spectra quantitatively. 7 The definition of the χ 2 was…”

Structural insights into the elastin mimetic (LGGVG)6 using solid‐state 13C NMR experiments and statistical analysis of the PDB

“…Solid-state nuclear magnetic resonance (NMR) spectroscopy, on the other hand, seems nearly ideal for the characterization of elastin and other fibrous proteins, such as amyloids, 6-8 collagen, 9,10 and silks. [11][12][13] Solid-state NMR has been used to show that there is likely a significant degree of heterogeneity in elastin, 14 as well as in mimetics of its hydrophobic domains. [15][16][17][18] Straightforward approaches, such as one-dimensional (1D) cross-polarization-with-magic-angle-spinning (CPMAS) 13 C NMR spectroscopy and related relaxation measurements, have been employed 14,15 in addition to significantly more sophisticated methods such as REDOR and 2D methods for the determination of internuclear distances and torsion angles, respectively.…”