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Covalently cross linked

Tiernan Thomas O'Malley, William M Wittbold, Sara Linse, Dominic M Walsh
Extracts of Alzheimer's disease (AD) brain that contain what appear to be SDS-stable amyloid β-protein (Aβ) dimers potently block LTP and impair memory consolidation. Brain-derived dimers can be physically separated from Aβ monomer, consist primarily of Aβ42 and resist denaturation by powerful chaotropic agents. In nature, covalently cross-linked Aβ dimers could be generated in only one of two different ways - either by the formation of a dityrosine (DiY) or an isopeptide ε-(γ-glutamyl)-lysine (Q-K) bond...
October 17, 2016: Biochemistry
Qiong Xiao, Qin Yin, Hui Ni, Huinong Cai, Changzheng Wu, Anfeng Xiao
Carboxyl functioned magnetic nanoparticles (CMNPs) were prepared by a simple co-precipitation method and characterized by Fourier transform infrared spedtroscopy and scanning electron microscope. The prepared CMNPs were used for covalent immobilization of the arylsulfatase which could be applied in desulfation of agar. The optimal immobilizaion conditions were obtained as follows: glutaraldehyde concentration 1.0% (v/v), cross-linking time 3h, immobilization time 3h, immobilization temperature 5°C and enzyme dose 0...
October 13, 2016: International Journal of Biological Macromolecules
Na Sai, Wenjing Sun, Yuntang Wu, Zhong Sun, Guanggui Yu, Guowei Huang
A new enzyme-linked immunosorbent assay (ELISA) for atrazine was developed based on covalent bonding of the small molecule hapten, 2-mercaptopropionic acid-4-ethylamino-6-isopropylamino-1,3,5-triazine (MPA-atrazine), to urea-glutaraldehyde (UGA)-treated microtiter plates. In this assay, the microtiter plate surface was treated with the UGA network to both introduce amino groups, which were used to cross-link with the hapten carboxylate groups, and efficiently prevent non-specific adsorption of antibodies, which successfully eliminated the time-consuming routine blocking step...
October 12, 2016: International Immunopharmacology
Chu Gong, Caicai Lu, Bingqiang Li, Meng Shan, Guolin Wu
Hydrogel systems based on cross-linked polymeric materials with adhesive properties in wet environments have been considered as promising candidates for tissue adhesives. The 3,4-dihydroxyphenylalanine (DOPA) is believed to be responsible for the water-resistant adhesive characteristics of mussel adhesive proteins. Under the inspiration of DOPA containing adhesive proteins, a dopamine-modified poly(α,β-aspartic acid) derivative (PDAEA) was successfully synthesized by successive ring-opening reactions of polysuccinimide (PSI) with dopamine and ethanolamine, and an injectable bioadhesive hydrogel was prepared via simply mixing PDAEA and FeCl3 solutions...
October 14, 2016: Journal of Biomedical Materials Research. Part A
Shyam K Konda, Celine Kelso, Jelena Medan, Brad E Sleebs, Don R Phillips, Suzanne M Cutts, J Grant Collins
The major covalent adduct formed between a (13)C-labelled formaldehyde activated bis-amino mitoxantrone analogue (WEHI-150) and the hexanucleotide d(CG(5Me)CGCG)2 has been isolated by HPLC chromatography and the structure determined by NMR spectroscopy. The results indicate that WEHI-150 forms one covalent bond through a primary amine to the N-2 of the G2 residue, with the polycyclic ring structure intercalated at the (5Me)C3pG4/G10p(5Me)C9 site. Furthermore, the WEHI-150 aromatic ring system is oriented approximately parallel to the long axis of the base pairs, with one aliphatic side-chain in the major groove and the other side-chain in the minor groove...
October 13, 2016: Organic & Biomolecular Chemistry
Sijun Liu, Lin Li
Combining an ionically cross-linked κ-carrageenan network with a covalently cross-linked polyacrylamide network, we have fabricated a κ-carrageenan/polyacrylamide double network (DN) hydrogel using a one-pot method. The resulting DN hydrogel exhibited a high elastic modulus of 280 kPa and a fracture energy of 6150 J/m2. A model has been proposed considering unzipping of double-helical aggregates and dissociation of double helices of κ-carrageenan, which could well interpret the continuous fracture process of the first κ-carrageenan network and the toughening mechanism of the physically and chemically cross-linked κ-carrageenan/polyacrylamide DN hydrogel...
October 10, 2016: ACS Applied Materials & Interfaces
Sylvie Neyertz, David Brown, Michiel J T Raaijmakers, Nieck E Benes
Hybrid organic/inorganic hyper-cross-linked membranes based on imides covalently bonded with polyhedral oligomeric silsesquioxanes (POSS) have recently been developed for gas-separation applications under high pressure and/or temperature conditions. Their molecular sieving capabilities have been shown to depend on the nature of the organic dianhydride precursor. In the present work, realistic molecular models of such polyPOSS-imide films based on the flexible 6FDA dianhydride are compared to those based on the shorter and more rigid PMDA dianhydride...
October 7, 2016: Physical Chemistry Chemical Physics: PCCP
Leopoldo Spadea, Emanuele Tonti, Enzo Maria Vingolo
Collagen cross-linking (CXL) is a relatively new conservative approach for progressive corneal ectasia, which is able to strengthen corneal tissue reforming new covalent bonds. Subjective and objective results following this method seem to be promising. In recent years, newer CXL protocols have been developed to perform more effective and less invasive procedures. The increasing diffusion of CXL in the corneal ectatic disease has increased the need to have actual indices regarding the efficacy of the treatment...
2016: Clinical Ophthalmology
Tonatiuh Molina-Villa, Valentín Mendoza, Fernando López-Casillas
By combining the powers of Affinity Labeling and Immunoprecipitation (AFLIP), a technique for the detection of low abundance receptors in zebrafish embryos has been implemented. This technique takes advantage of the selectivity and sensitivity conferred by affinity labeling of a given receptor by its ligand with the specificity of the immunoprecipitation. We have used AFLIP to detect the type III TGF-β receptor (TGFBR3), also know as betaglycan, during early zebrafish development. AFLIP was instrumental in validating the efficacy of a TGFBR3 morphant zebrafish phenotype...
2016: Journal of Visualized Experiments: JoVE
Helen Troilo, Ruth Steer, Richard F Collins, Cay M Kielty, Clair Baldock
TGFβ plays key roles in fibrosis and cancer progression, and latency is conferred by covalent linkage to latent TGFβ binding proteins (LTBPs). LTBP1 is essential for TGFβ folding, secretion, matrix localization and activation but little is known about its structure due to its inherent size and flexibility. Here we show that LTBP1 adopts an extended conformation with stable matrix-binding N-terminus, extended central array of 11 calcium-binding EGF domains and flexible TGFβ-binding C-terminus. Moreover we demonstrate that LTBP1 forms short filament-like structures independent of other matrix components...
September 28, 2016: Scientific Reports
Robert B Quast, Biljana Ballion, Marlitt Stech, Andrei Sonnabend, Balázs R Varga, Doreen A Wüstenhagen, Péter Kele, Stefan M Schiller, Stefan Kubick
Cell-free protein synthesis systems represent versatile tools for the synthesis and modification of human membrane proteins. In particular, eukaryotic cell-free systems provide a promising platform for their structural and functional characterization. Here, we present the cell-free synthesis of functional human epidermal growth factor receptor and its vIII deletion mutant in a microsome-containing system derived from cultured Sf21 cells. We provide evidence for embedment of cell-free synthesized receptors into microsomal membranes and asparagine-linked glycosylation...
September 27, 2016: Scientific Reports
Muhammad Bilal, Hafiz M N Iqbal, Syed Zakir Hussain Shah, Hongbo Hu, Wei Wang, Xuehong Zhang
In this study, horseradish peroxidase (HRP) was covalently immobilized on the calcium-alginate support using glutaraldehyde (GA) as a cross-linking reagent for detoxification and degradation of synthetic dyes. Immobilization procedure furnished significant immobilization efficiency (86.27 ± 3.43%) along with apparent and relative activity of 24.39 ± 1.03 U/g and 84.97 ± 3.54%, respectively, for immobilized-HRP. In comparison to free-state, immobilized-HRP catalyzed the substrate oxidation reaction in a slightly acidic and wider temperature range, with an optimum at 60 °C...
December 1, 2016: Journal of Environmental Management
Thomas A Collier, Anthony Nash, Helen L Birch, Nora H de Leeuw
Covalently cross-linked advanced glycation end products (AGE) are among the major post-translational modifications to proteins as a result of non-enzymatic glycation. The formation of AGEs has been shown to have adverse effects on the properties of the collagenous tissue; they are even linked to a number of age related disorders. Little is known about the sites at which these AGEs form or why certain sites within the collagen are energetically more favourable than others. In this study we have used a proven fully atomistic molecular dynamics approach to identify six sites where the formation of the intra-molecular 3-deoxyglucosone-derived imidazolium cross-link (DOGDIC) is energetically favourable...
November 2016: Biophysical Chemistry
Ali Reza Karimi, Azam Khodadadi
Fabrication of hydrogels based on chitosan (CS) with superb self-healing behavior and high mechanical and electrical properties has become a challenging and fascinating topic. Most of the conventional hydrogels lack these properties at the same time. Our objectives in this research were to synthesize, characterize, and evaluate the general properties of chitosan covalently cross-linked with zinc phthalocyanine tetra-aldehyde (ZnPcTa) framework. Our hope was to access an unprecedented self-healable three-dimensional (3D) nanostructure that would harvest the superior mechanical and electrical properties associated with chitosan...
October 12, 2016: ACS Applied Materials & Interfaces
Christopher M Madl, Lily M Katz, Sarah C Heilshorn
Covalently-crosslinked hydrogels are commonly used as 3D matrices for cell culture and transplantation. However, the crosslinking chemistries used to prepare these gels generally cross-react with functional groups present on the cell surface, potentially leading to cytotoxicity and other undesired effects. Bio-orthogonal chemistries have been developed that do not react with biologically relevant functional groups, thereby preventing these undesirable side reactions. However, previously developed biomaterials using these chemistries still possess less than ideal properties for cell encapsulation, such as slow gelation kinetics and limited tuning of matrix mechanics and biochemistry...
June 7, 2016: Advanced Functional Materials
C C O'Sullivan, M Lindenberg, C Bryla, N Patronas, C J Peer, L Amiri-Kordestani, N Davarpanah, E M Gonzalez, M Burotto, P Choyke, S M Steinberg, D J Liewehr, W D Figg, T Fojo, S Balasubramaniam, S E Bates
PURPOSE: Improved therapies and imaging modalities are needed for the treatment of breast cancer brain metastases (BCBM). ANG1005 is a drug conjugate consisting of paclitaxel covalently linked to Angiopep-2, designed to cross the blood-brain barrier. We conducted a biomarker substudy to evaluate (18)F-FLT-PET for response assessment. METHODS: Ten patients with measurable BCBM received ANG1005 at a dose of 550 mg/m(2) IV every 21 days. Before and after cycle 1, patients underwent PET imaging with (18)F-FLT, a thymidine analog, retention of which reflects cellular proliferation, for comparison with gadolinium-contrast magnetic resonance imaging (Gd-MRI) in brain metastases detection and response assessment...
November 2016: Breast Cancer Research and Treatment
H A Calderon, A Okonkwo, I Estrada-Guel, V G Hadjiev, F Alvarez-Ramírez, F C Robles Hernández
We present experimental evidence under low-dose conditions transmission electron microscopy for the unfolding of the evolving changes in carbon soot during mechanical milling. The milled soot shows evolving changes as a function of the milling severity or time. Those changes are responsible for the transformation from amorphous carbon to graphenes, graphitic carbon, and highly ordered structures such as morphed graphenes, namely Rh6 and Rh6-II. The morphed graphenes are corrugated layers of carbon with cross-linked covalently nature and sp(2)- or sp(3)-type allotropes...
2017: Adv Struct Chem Imaging
Amnon Golan, Ning Wei, Elah Pick
The COP9 signalosome (CSN) is an evolutionary conserved complex that is found in all eukaryotes, and implicated in regulating the activity of Cullin-RING ubiquitin Ligases (CRLs). Activity of CRLs is highly regulated; complexes are active when the cullin subunit is covalently attached to the ubiquitin like modifier, Nedd8. Neddylation/deneddylation cycles are required for proper CRLs activity, and deneddylation is performed by the CSN complex.We describe here a method utilizing resin-coupled antibodies to deplete the CSN from human cell extracts, and to obtain endogenous CSN complexes by immunopurification...
2016: Methods in Molecular Biology
Cesare Benedetti, Alessandro Cazzolaro, Mauro Carraro, Robert Graf, Katharina Landfester, Silvia Gross, Rafael Muñoz-Espí
Organic-inorganic hybrid nanoparticles are prepared by free-radical copolymerization of methyl methacrylate (MMA) with the structurally well-defined methacrylate-functionalized zirconium oxocluster Zr4O2(methacrylate)12. The polymerization process occurs in the confined space of miniemulsion droplets. The formation of covalent chemical bonds between the organic and the inorganic counterparts improves the distribution of the guest species (oxoclusters) in the polymer particles, overcoming problems related to migration, leaching, and stability...
October 5, 2016: ACS Applied Materials & Interfaces
Johannes Hellwig, Samantha Micciulla, Julia Strebe, Regine von Klitzing
Atomic force microscopy (AFM) is used to carry out rheology measurements on the nanoscale and to determine the mechanical properties of poly(l-lysine) (PLL)/hyaluronic acid (HA) multilayer films. Storage (G') and loss modulus (G″) of the films are calculated and compared with the values obtained from quartz crystal microbalance with dissipation monitoring measurements (QCM-D). A predominant elastic behavior independently of the applied frequencies (5-100 Hz) is observed for native HA/PLL films consisting of 36 double layer...
October 4, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
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