Chain-Folded Lamellar Stacking Structure of the Crystalline Fraction of Silk Fibroin with Silk II Form Studied by 2D C-C Homonuclear Correlation NMR Spectroscopy.

The structure of silk fibroin (SF) is a subject of significant interest due to its remarkable physical properties; however, its atomic-level structure is still not conclusive. We previously proposed a lamellar stacking structure for the crystalline fraction (Cp) with β-turns occurring every eighth amino acid. In this study, we took the following steps: At first, a model of the chain-folded lamellar stacking structure in antipolar and antiparallel β-sheet layers was constructed.

Lamellar Structure in Alanine-Glycine Copolypeptides Studied by Solid-State NMR Spectroscopy: A Model for the Crystalline Domain of Silk Fibroin in Silk II Form.

silk fibroin (SF) fibers with excellent mechanical properties have attracted widespread attention as new biomaterials. However, the structural details are still not conclusive. Here, we propose a lamellar structure for the crystalline domain of the SF fiber based on structural analyses of the Ala Cβ peaks in the C cross-polarization/magic angle spinning NMR spectra of (Ala-Gly) ( = 9, 12, 15, and 25) and C selectively labeled (Ala-Gly) model peptides.

Infrared-A Irradiation-induced Inhibition of Human Keratinocyte Proliferation and Potential Mechanisms.

Infrared-A (IRA), which can penetrate deeply into the human skin, is a major component of solar radiation and is recognized to promote photoaging of human dermis. To our knowledge, however, the cellular and molecular consequences of human epidermis exposure to IRA have not been clarified. Thus, we investigated whether IRA inhibits the proliferation of normal human epidermal keratinocytes (NHEKs).

Packing Structure of Antiparallel β-Sheet Polyalanine Region in a Sequential Model Peptide of Dragline Silk Studied Using C Solid-State NMR and MD Simulation.

Packing structures of polyalanine regions, which are considered to be the reason for the extremely high strength of spider dragline silks, were studied using a series of sequential peptides: (Glu)GlyGlyLeuGlyGlyGlnGlyAlaGly(Ala)GlyGlyAlaGlyGlnGlyGlyTyrGlyGly(Glu) ( = 3-8) using C solid-state NMR spectroscopy. The conformations of (Ala) in the freeze-dried peptides changed gradually with increasing n from random coils to α-helices with partial antiparallel β-sheet (AP-β) structures. Conversely, all the insolubilized peptides, = 6-8 after low-pH treatment and = 4-8 after formic acid/methanol treatment, formed AP-β structures with significant amounts of staggered packing arrangements.

Conformational change of C-labeled 47-mer model peptides of Nephila clavipes dragline silk in poly(vinyl alcohol) film by stretching studied by C solid-state NMR and molecular dynamics simulation.

For determination of the conformation of irregular sequences in glycine-rich region of the Nephila clavipes spider dragline silk, the combination of C selectively labeled model peptides for the typical primary structure and their C solid-state NMR observations is very useful (T. Asakura et al. Macromolecules.

Structural Analyses of Alanine Trimer and Tetramer Crystals with Antiparallel and Parallel β-Sheet Structures Using Solid-State H Spin-Diffusion 2D Correlation NMR Spectroscopy.

Poly-l-alanine (PLA) sequences are key elements of the crystalline domains of spider dragline and wild silkworm silks. In the present work, H spin-diffusion two-dimensional (2D) correlation NMR spectra were observed for selectively deuterated (Ala) and (Ala) crystals to develop the analytical method for the structure of PLA sequences. The build-up curves of the cross peaks for three kinds of H pairs in selectively deuterated (Ala) and (Ala) crystals were observed to obtain spin-diffusion rate constant k from relaxation master equations P (τ).

Quantitative Analysis of Solid-State Homonuclear Correlation Spectra of Antiparallel β-Sheet Alanine Tetramers.

Poly-l-alanine (PLA) sequences are a key element in the structure of the crystalline domains of spider dragline silks, wild silkworm silks, antifreeze proteins, and amyloids. To date, no atomic-level structures of antiparallel (AP)-PLA longer than Ala have been reported using the single-crystal X-ray diffraction analysis. In this work, dipolar-assisted rotational resonance solid-state NMR spectra were observed to determine the effective internuclear distances of C uniformly labeled alanine tetramer with antiparallel (AP) β-sheet structure whose atomic coordinates are determined from the X-ray crystallographic analysis.

Refined Crystal Structure of Samia cynthia ricini Silk Fibroin Revealed by Solid-State NMR Investigations.

Samia cynthia ricini is one of the wild silkworms and its silk fibroin (SF) consists of alternatively repeating poly-l-alanine (PLA) sequences as crystalline domain and glycine-rich sequences as noncrystalline domain; the structure is similar to those of spider silk and other wild silkworm silks. In this paper, we proposed a new staggered model for the packing arrangement of the PLA sequence through the use of the Cambridge Serial Total Energy Package program and a comparison of the observed and calculated chemical shifts of the PLA sequence with the Gauge Including Projector Augmented Wave method. The new model was supported by the interatomic distance information from the cross peaks of Ala Cβ dipolar-assisted rotational resonance (DARR) spectrum of the PLA sequences in S.

Packing arrangement of C selectively labeled sequence model peptides of Samia cynthia ricini silk fibroin fibers studied by solid-state NMR.

Samia cynthia ricini (S. c. ricini) is one of the wild silkworms.

Glycerin-Induced Conformational Changes in Bombyx mori Silk Fibroin Film Monitored by (13)C CP/MAS NMR and ¹H DQMAS NMR.

In order to improve the stiff and brittle characteristics of pure Bombyx mori (B. mori) silk fibroin (SF) film in the dry state, glycerin (Glyc) has been used as a plasticizer. However, there have been very limited studies on the structural characterization of the Glyc-blended SF film.

Parallel β-Sheet Structure of Alanine Tetrapeptide in the Solid State As Studied by Solid-State NMR Spectroscopy.

The structural analysis of alanine oligopeptides is important for understanding the crystalline region in silks from spiders and wild silkworms and also the mechanism of cellular toxicity of human diseases arising from expansion in polyalanine sequences. The atomic-level structures of alanine tripeptide and tetrapeptide with antiparallel β-sheet structures (AP-Ala3 and AP-Ala4, respectively) together with alanine tripeptide with parallel β-sheet structures (P-Ala3) have been determined, but alanine tetrapeptide with a parallel β-sheet structure (P-Ala4) has not been reported yet. In this article, first, we established the preparation protocol of P-Ala4 from more stable AP-Ala4.

NMR study of the structures of repeated sequences, GAGXGA (X = S, Y, V), in Bombyx mori liquid silk.

The silk fibroin stored in the silk gland of the Bombyx mori silkworm, called "liquid silk", is spun out and converted into the silk fiber with extremely high strength and high toughness. Therefore it is important to determine the silk structure before spinning called Silk I at an atomic level to clarify the fiber formation mechanism. We proposed the repeated type II β-turn structure as Silk I in the solid state with the model peptide (AG)15 and several solid state NMR techniques previously.

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.

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.

Rebamipide increases the mucin-like glycoprotein production in corneal epithelial cells.

Purpose: Dry eye is a multifactorial disease of tears and the ocular surface due to tear deficiency or excessive tear evaporation. Tear film instability is due to a disturbance in ocular surface mucin leading to a dysfunction of mucin, resulting in dry eye. In this study, we examined the effect of rebamipide, an anti-ulcer agent, on glycoconjugate production, as an indicator of mucin-like glycoprotein in cultured corneal epithelial cells.

Lamellar structure in poly(ala-gly) determined by solid-state NMR and statistical mechanical calculations.

Lamellar structure of poly(Ala-Gly) or (AG)n in the solid was examined using 13C solid-state NMR and statistical mechanical approaches. Two doubly labeled versions, [1-13C]Gly14[1-13C]Ala15- and [1-13C]Gly18[1-13C]Ala19 of (AG)15 were examined by two-dimensional (2D) 13C spin diffusion NMR in the solid state. In addition five doubly labeled [15N,13C]-versions of the same peptide, (AG) 15 and 15 versions labeled [3-13C] in each of the successive Ala residues were utilized for REDOR and 13C CP/MAS NMR measurements, respectively.