Matching Items (3)

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Secondary Structure Adopted by the Gly-Gly-X Repetitive Regions of Dragline Spider Silk

Description

Solid-state NMR and molecular dynamics (MD) simulations are presented to help elucidate the molecular secondary structure of poly(Gly-Gly-X), which is one of the most common structural repetitive motifs found in

Solid-state NMR and molecular dynamics (MD) simulations are presented to help elucidate the molecular secondary structure of poly(Gly-Gly-X), which is one of the most common structural repetitive motifs found in orb-weaving dragline spider silk proteins. The combination of NMR and computational experiments provides insight into the molecular secondary structure of poly(Gly-Gly-X) segments and provides further support that these regions are disordered and primarily non-β-sheet. Furthermore, the combination of NMR and MD simulations illustrate the possibility for several secondary structural elements in the poly(Gly-Gly-X) regions of dragline silks, including β-turns, 3[subscript 10]-helicies, and coil structures with a negligible population of α-helix observed.

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Date Created
  • 2016-12-02

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Investigating Lysine Adsorption on Fumed Silica Nanoparticles

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The adsorption of amino acids on silica surfaces has attracted considerable interest because it has a broad range of applications in various fields such as drug delivery, solid-phase peptide synthesis,

The adsorption of amino acids on silica surfaces has attracted considerable interest because it has a broad range of applications in various fields such as drug delivery, solid-phase peptide synthesis, and biocompatible materials synthesis. In this work, we systematically study lysine adsorption on fumed silica nanoparticles with thermal analysis and solid-state NMR. Thermogravimetric analysis results show that the adsorption behavior of lysine in low-concentration aqueous solutions is well-described by the Langmuir isotherm. With ultrafast magic-angle-spinning 1H NMR and multinuclear and multidimensional 13C and 15N solid-state NMR, we successfully determine the protonation state of bulk lysine and find that lysine is adsorbed on silica nanoparticle surfaces through the side-chain amine groups. Density functional theory calculations carried out on lysine and lysine–silanol complex structures further confirm that the side-chain amine groups interact with the silica surface hydroxyl groups via strong hydrogen bonding. Furthermore, we find that lysine preferentially has monolayer coverage on silica surfaces in high salt concentration solutions because of the ionic complexes formed with surface bound lysine molecules.

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Date Created
  • 2014-11-06

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Nuclear magnetic resonance (NMR) spectroscopic characterization of nanomaterials and biopolymers

Description

Nanomaterials have attracted considerable attention in recent research due to their wide applications in various fields such as material science, physical science, electrical engineering, and biomedical engineering. Researchers have developed

Nanomaterials have attracted considerable attention in recent research due to their wide applications in various fields such as material science, physical science, electrical engineering, and biomedical engineering. Researchers have developed many methods for synthesizing different types of nanostructures and have further applied them in various applications. However, in many cases, a molecular level understanding of nanoparticles and their associated surface chemistry is lacking investigation. Understanding the surface chemistry of nanomaterials is of great significance for obtaining a better understanding of the properties and functions of the nanomaterials. Nuclear magnetic resonance (NMR) spectroscopy can provide a familiar means of looking at the molecular structure of molecules bound to surfaces of nanomaterials as well as a method to determine the size of nanoparticles in solution. Here, a combination of NMR spectroscopic techniques including one- and two-dimensional NMR spectroscopies was used to investigate the surface chemistry and physical properties of some common nanomaterials, including for example, thiol-protected gold nanostructures and biomolecule-capped silica nanoparticles.

Silk is a natural protein fiber that features unique properties such as excellent mechanical properties, biocompatibility, and non-linear optical properties. These appealing physical properties originate from the silk structure, and therefore, the structural analysis of silk is of great importance for revealing the mystery of these impressive properties and developing novel silk-based biomaterials as well. Here, solid-state NMR spectroscopy was used to elucidate the secondary structure of silk proteins in N. clavipes spider dragline silk and B. mori silkworm silk. It is found that the Gly-Gly-X (X=Leu, Tyr, Gln) motif in spider dragline silk is not in a β-sheet or α-helix structure and is very likely to be present in a disordered structure with evidence for 31-helix confirmation. In addition, the conformations of the Ala, Ser, and Tyr residues in silk fibroin of B. mori were investigated and it indicates that the Ala, Ser, and Tyr residues are all present in disordered structures in silk I (before spinning), while show different conformations in silk II (after spinning). Specifically, in silk II, the Ala and Tyr residues are present in both disordered structures and β-sheet structures, and the Ser residues are present primarily in β-sheet structures.

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Date Created
  • 2017