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Covalently cross linked

G Portale, J Torbet
The structure of the core scaffold of blood clots, the interlinked 3-dimensional network of fibrin fibers, is modified by mechanical forces generated by platelet driven clot retraction, wound repair and shear stress through blood flow. Here X-ray diffraction is used to investigate how uniaxial strain, ε (ε = extension/original length), alters fiber structure in highly aligned human plasma clots covalently cross-linked by Factor XIIIa. Three stretch sensitive axially repeating structures are identified. Firstly, the foundation structure with an initial ≈22 nm axial repeat stretches, fades then disappears at ε ≈ 0...
May 21, 2018: Nanoscale
Eugen Schechtel, Yaping Yan, Xiangfan Xu, Yu Cang, Wolfgang Tremel, Zuyuan Wang, Baowen Li, George Fytas
Metal oxide based polymer nanocomposites find diverse applications as functional materials, and in particular thiol-ene/TiO2 nanocomposites are promising candidates for dental restorative materials. The important mechanical and thermal properties of the nanocomposites, however, are still not well understood. In this study, the elastic modulus and thermal conductivity of thiol-ene/TiO2 nanocomposite thin films with varying weight fractions of TiO2 nanoparticles are investigated by using Brillouin light scattering spectroscopy and 3ω measurements, respectively...
November 16, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
Hongqiang Dong, Mingcheng Guo, You Liang, Chen Fan, Guanglong Ding, Wenbing Zhang, Gang Tang, Jiale Yang, Dandan Kong, Yongsong Cao
Indole-3-butyric acid (IBA) is an efficient plant growth regulator for promoting germination and the formation of rooting of various plants. Since it is unstable and presents the low utilization ratio, there is a compelling need to design an environmentally friendly formulation for IBA, which can reduce the loss of degradation and improve its utilization. Nano-sized controlled-release formulations can provide better durability and penetrate through the plant epidermis to efficiently deliver the agrochemicals to the target tissues...
August 1, 2018: Materials Science & Engineering. C, Materials for Biological Applications
Fei Tao, He Jiang, Wenwei Chen, Yongyong Zhang, Jiarong Pan, Jiaxin Jiang, Zhenbao Jia
BACKGROUND: Soy protein isolate (SPI) has promising applications in various food products because of its excellent functional properties and nutritional quality. The structural and emulsifying properties of covalently modified SPI by (-)-epigallocatechin-3-gallate (EGCG) were investigated. RESULTS: SPI was covalently modified by EGCG under alkaline conditions. SDS-PAGE analysis revealed that EGCG modification caused cross-linking of SPI proteins. Circular dichroism spectra demonstrated that the secondary structure of SPI proteins was changed by EGCG modification...
May 7, 2018: Journal of the Science of Food and Agriculture
Huong T H Nguyen, Prokopis C Andrikopoulos, Lubomír Rulíšek, Christopher J Shaffer, František Tureček
We report a gas-phase UV photodissociation study investigating non-covalent interactions between neutral hydrophobic pentapeptides and peptide ions incorporating a diazirine-tagged photoleucine residue. Phenylalanine (Phe) and proline (Pro) were chosen as the conformation-affecting residues that were incorporated into a small library of neutral pentapeptides. Gas-phase ion-molecule complexes of these peptides with photo-labeled pentapeptides were subjected to photodissociation. Selective photocleavage of the diazirine ring at 355 nm formed short-lived carbene intermediates that underwent cross-linking by insertion into H-X bonds of the target peptide...
May 7, 2018: Journal of the American Society for Mass Spectrometry
Elena Kudryashova, David B Heisler, Blake Williams, Alyssa J Harker, Kyle Shafer, Margot E Quinlan, David R Kovar, Dimitrios Vavylonis, Dmitri S Kudryashov
Delivery of bacterial toxins to host cells is hindered by host protective barriers. This obstruction dictates a remarkable efficiency of toxins, a single copy of which may kill a host cell. Efficiency of actin-targeting toxins is further hampered by an overwhelming abundance of their target. The actin cross-linking domain (ACD) toxins of Vibrio species and related bacterial genera catalyze the formation of covalently cross-linked actin oligomers. Recently, we reported that the ACD toxicity can be amplified via a multivalent inhibitory association of actin oligomers with actin assembly factors formins, suggesting that the oligomers may act as secondary toxins...
April 21, 2018: Current Biology: CB
Ekaterina S Ilina, Svetlana N Khodyreva, Olga I Lavrik
Clustered apurinic/apyrimidinic (AP) sites are more cytotoxic than isolated AP lesions because double strand breaks (DSB) can be formed during repair of closely positioned bistranded AP sites. Formation of DSB due to simultaneous cleavage of bistranded AP sites may be regulated by proteins specifically interacting with this complex lesion. A set of AP DNA duplexes containing AP sites in both strands in different mutual orientation (BS-AP DNAs) was used for search in the extracts of human cells proteins specifically recognizing clustered AP sites...
May 3, 2018: Biochimie
MIchele Baglioni, Joana Domingues, Emiliano Carretti, Emiliano Fratini, David Chelazzi, Rodorico Giorgi, Piero Baglioni
The removal of aged varnishes from the surface of easel paintings using the common conservation practice (i.e by means of organic solvents) often causes pigment leaching, paint loss and varnish re-deposition. Recently we proposed an innovative cleaning system based on semi-interpenetrated polymer networks (SIPN), where a covalently cross-linked poly(hydroxyethyl methacrylate), pHEMA, network is interpenetrated by linear chains of poly(vinylpyrrolidone), PVP. This chemical gel, simply loaded with water, was designed to safely remove surface dirt from water-sensitive artifacts...
May 4, 2018: ACS Applied Materials & Interfaces
Christopher P Kabb, Christopher S O'Bryan, Christopher C Deng, Thomas E Angelini, Brent S Sumerlin
Reversible covalent chemistry provides access to robust materials with the ability to be degraded and reformed upon exposure to an appropriate stimulus. Photoresponsive units are attractive for this purpose, as the spatial and temporal application of light is easily controlled. Coumarin derivatives undergo a [2 + 2] cycloaddition upon exposure to long-wave UV irradiation (365 nm), and this process can be reversed using short-wave UV light (254 nm). Therefore, polymers cross-linked by coumarin groups are excellent candidates as reversible covalent gels...
May 4, 2018: ACS Applied Materials & Interfaces
Frantisek Turecek, Yang Liu, Zachary Ramey
The small neuroprotective peptide Cys-Ala-Gln-Lys (CAQK) was selectively tagged with a diazirine group and its photochemical cross-linking was studied with model target peptides. Experimental results in combination with Born-Oppenheimer molecular dynamics revealed the structural preferences for binding to the amino acid residues in the target peptides. Effects of the target peptide sequence and N- and C-terminal modifications are discussed.
May 3, 2018: Chemistry: a European Journal
Apostolos Salmatonidis, Jutta Hesselbach, Gerhard Lilienkamp, Tobias Graumann, Winfried Daum, Arno Kwade, Georg Garnweitner
Titania nanoparticle-based thin films are highly attractive for a vast range of commercial applications. Whilst their application on polymer-based substrates is particularly appealing, the requirement of low process temperatures results in low mechanical stability. Highly crystalline anatase nanoparticles were used as the building blocks for coatings through a two-stage process. The main benefits of this method, over the more common sol-gel ones, are the relatively low temperature required for the production of metal oxide coatings, allowing the use of polymer-based substrates, and the defined crystallinity of the resulting thin films...
May 3, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Aruna Bitra, Tzanko Doukov, Michael Croft, Dirk M Zajonc
Human (h)4-1BB (TNFRSF9 or CD137) is an inducible tumor necrosis factor receptor (TNFR) super family member that interacts with its cognate ligand h4-1BBL to promote T lymphocyte activation and proliferation. h4-1BB is currently being targeted with agonists in cancer immunotherapy. Here, we determined the crystal structures of unbound h4-1BBL and both wildtype h4-1BB and a dimerization-deficient h-41BB mutant (C121S) in complex with h4-1BBL at resolutions between 2.7 Å and 3.2 Å. We observed that the structural arrangement of 4-1BBL, both unbound and in the complex, represents the canonical bell shape as seen in other similar TNF proteins and differs from the previously reported three-bladed propeller structure of 4-1BBL...
May 2, 2018: Journal of Biological Chemistry
Zeyang Li, Guan-Yu Chen
Recent advances in the development of immunosensors using polymeric nanomaterials and nanoparticles have enabled a wide range of new functions and applications in diagnostic and prognostic research. One fundamental challenge that all immunosensors must overcome is to provide the specificity of target molecular recognition by immobilizing antibodies, antibody fragments, and/or other peptides or oligonucleotide molecules that are capable of antigen recognition on a compact device surface. This review presents progress in the application of immobilization strategies including the classical adsorption process, affinity attachment, random cross-linking and specific covalent linking...
April 26, 2018: Nanomaterials
Gajanan S Ghodake, Jiwook Yang, Surendra S Shinde, Bhupendra M Mistry, Dae-Young Kim, Jung-Suk Sung, Avinash A Kadam
Enormous disposal of paper wastes (PW) causing number of environmental problems. PW is efficiently used to extract multifunctional α-cellulose fibers (αCFs). Thus, αCFs extraction from PW, and functionalization with Fe3 O4 and chitosan were successfully performed for immobilization of laccase. Therefore, in this investigation, PW extracted αCFs were tuned with supermagnetic Fe3 O4 (M) and functionalized with chitosan (CTA) (M-PW-αCF-CTA). Furthermore, M-PW-αCF-CTA was glutaraldehyde cross-linked for covalent laccase immobilization...
April 14, 2018: Bioresource Technology
Doudou Lou, Lin Fan, Yan Cui, Yefei Zhu, Ning Gu, Yu Zhang
Performance of nanoprobes can often determine the detection level of Lateral immunochromatography. Traditional probes were limited by the quantity and orientation of antibodies, immune activity of the Fab region or binding strength between protein and substrate. This study developed a new efficient and robust technology to construct fluorescent nanoprobes with oriented modified antibodies, based on specific binding of the Fc region of antibody with streptococcal protein G (SPG) on the surface of polystyrene microspheres (MS) and subsequent covalent cross linking at binding sites to firm them...
April 26, 2018: Analytical Chemistry
Enlai Gao, Zhiping Xu
The precisely controlled size of nanoscale fluidic channels plays a critical role in resolving the permeation-selectivity trade-off in separation and filtration applications, where highly efficient gas separation and water desalination are targeted. Inspired by natural nacre where the spacing between mineral platelets changes upon applying tension as fractured mineral bridges climb over each other, bio-inspired graphene-derived membranes with sheets cross-linked by aligned covalent bonds are proposed in design, to ensure a controlled interlayer spacing ranging from 4 Å to 14 Å while preserving structural and mechanical stabilities by prohibiting swelling...
April 26, 2018: Nanoscale
Hiroshi Nishimura, Akihiro Kamiya, Takashi Nagata, Masato Katahira, Takashi Watanabe
Cross-linking between lignin and polysaccharide in plant cell-wall determines physical, chemical, and biological features of lignocellulosic biomass. Since Erdmann's first report in 1866, numerous studies have suggested the presence of a bond between hemicelluloses and lignin; however, no clear evidence for this interaction has been reported. We describe the first direct proof of covalent bonding between plant cell-wall polysaccharides and lignin. Nuclear magnetic resonance spectroscopy was used to observe the long-range correlations through an α-ether bond between lignin and the primary hydroxyl group of a mannose residue in glucomannan...
April 25, 2018: Scientific Reports
William Merritt, Anne Marie Holter, Sharna Beahm, Connor Gonzalez, Timothy A Becker, Aaron Tabor, Andrew F Ducruet, Laura S Bonsmann, Trevor R Cotter, Sergey Frenklakh
BACKGROUND: Untreated ischemic stroke can lead to severe morbidity and death, and as such, there are numerous endovascular blood-clot removal (thrombectomy) devices approved for human use. Human thrombi types are highly variable and are typically classified in qualitative terms - 'soft/red,' 'hard/white,' or 'aged/calcified.' Quantifying human thrombus properties can accelerate the development of thrombus analogs for the study of thrombectomy outcomes, which are often inconsistent among treated patients...
April 25, 2018: Journal of Neurointerventional Surgery
Shu-Wei Wu, Xifeng Liu, A Lee Miller, Yu-Shiuan Cheng, Ming-Long Yeh, Lichun Lu
In the present study, we fabricated non-toxic, injectable, and thermo-sensitive NIPAAm-g-chitosan (NC) hydrogels with thiol modification for introduction of disulfide cross-linking strategy. Previously, NIPAAm and chitosan copolymer has been proven to have excellent biocompatibility, biodegradability and rapid phase transition after injection, suitable to serve as cell carriers or implanted scaffolds. However, weak mechanical properties significantly limit their potential for biomedical fields. In order to overcome this issue, we incorporated thiol side chains into chitosan by covalently conjugating N-acetyl-cysteine (NAC) with carbodiimide chemistry to strengthen mechanical properties...
July 15, 2018: Carbohydrate Polymers
Junzhe Lou, Fang Liu, Christopher D Lindsay, Ovijit Chaudhuri, Sarah C Heilshorn, Yan Xia
Injectable and biocompatible hydrogels have become increasingly important for cell transplantation to provide mechanical protection of cells during injection and a stable scaffold for cell adhesion post-injection. Injectable hydrogels need to be easily pushed through a syringe needle and quickly recover to a gel state, thus generally requiring noncovalent or dynamic cross-linking. However, a dilemma exists in the design of dynamic hydrogels: hydrogels with fast exchange of cross-links are easier to eject using less force, but lack long-term stability; in contrast, slow exchange of cross-links improves stability, but compromises injectability and thus the ability to protect cells under flow...
April 23, 2018: Advanced Materials
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