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Covalently cross linked

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https://www.readbyqxmd.com/read/29334089/asymmetric-4-2-annulations-to-construct-norcamphor-scaffolds-with-2-cyclopentenone-via-double-amine-thiol-catalysis
#1
Qian-Qian Yang, Wei Xiao, Wei Du, Qin Ouyang, Ying-Chun Chen
An efficient double catalytic system, combining chiral amine and 2-mercaptobenzoic acid, is applied for α',β-regioselective [4+2] annulations of 2-cyclopentenone with a diversity of activated alkenes, constructing multifunctional chiral bicycle[2,2,1]heptane scaffolds in good to excellent yields and enantioselectivities. In comparison with the traditional cross-dienamine species between 2-cyclopentenone and chiral amine, the interrupted enamine intermediate containing a covalently linked thiol catalyst shows significantly improved reactivity...
January 15, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29323888/covalent-immobilization-of-cellulase-using-magnetic-poly-ionic-liquid-support-improvement-of-the-enzyme-activity-and-stability
#2
Seyed Hassan Hosseini, Seyedeh Ameneh Hosseini, Nasrin Zohreh, Mahshid Yaghoubi, Ali Pourjavadi
A magnetic nanocomposite was prepared by entrapment of Fe3O4 nanoparticles into the cross-linked ionic liquid/epoxy type polymer. The resulting support was used for covalent immobilization cellulase through the reaction with epoxy groups. The ionic surface of the support improved the adsorption of enzyme and a large amount of enzyme (106.1 mg/g) was loaded onto the support surface. The effect of the presence of ionic monomer and covalent binding of enzyme was also investigated. The structures of supports were characterized by various instruments such as FT-IR, TGA, VSM, XRD, TEM, SEM and DLS...
January 11, 2018: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/29313337/improved-reversible-cross-linking-based-solid-phase-rna-extraction-for-pathogen-diagnostics
#3
Fei Zhao, Eun Yeong Lee, Yong Shin
In this study, we developed an amine-functionalized, diatomaceous earth-based, dimethyl suberimidate assisted (ADD) system as a novel binding strategy to improve solid-phase extraction method for rapid and simple purification of RNA from biological samples including human cells and pathogenic bacteria. This ADD system is based on reversible cross-linking reactions between RNA and the silica matrix. The formation of robust covalent bonds protects RNA from both the sufferance of washing steps and isolation with ribonuclease (RNase)-rich samples, leading to the extraction of higher quality RNA...
January 9, 2018: Analytical Chemistry
https://www.readbyqxmd.com/read/29310773/analysis-of-collagen-and-elastin-cross-links
#4
Mitsuo Yamauchi, Yuki Taga, Shunji Hattori, Masashi Shiiba, Masahiko Terajima
Fibrillar collagens represent the most abundant extracellular matrix proteins in vertebrates providing tissues and organs with form, stability, and connectivity. For such mechanical functions, the formation of covalent intermolecular cross-linking between molecules is essential. This process, the final posttranslational modification during collagen biosynthesis, is initiated by conversion of specific lysine and hydroxylysine residues to the respective aldehydes by the action of lysyl oxidases. This conversion triggers a series of condensation reactions with the juxtaposed lysine-aldehyde, lysine, hydroxylysine, and histidine residues within the same and neighboring molecules resulting in di-, tri-, and tetravalent cross-links...
2018: Methods in Cell Biology
https://www.readbyqxmd.com/read/29308094/stimulus-responsive-block-copolymer-nano-objects-and-hydrogels-via-dynamic-covalent-chemistry
#5
Renhua Deng, Yin Ning, Elizabeth R Jones, Victoria J Cunningham, Nicholas J W Penfold, Steven P Armes
Herein we demonstrate that dynamic covalent chemistry can be used to induce reversible morphological transitions in block copolymer nano-objects and hydrogels. Poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymer nano-objects (vesicles or worms) were prepared via polymerization-induced self-assembly. Addition of 4-carboxyphenylboronic acid (CPBA) leads to the formation of phenylboronate ester bonds with the 1,2-diol pendent groups on the hydrophilic PGMA stabilizer chains; such binding causes a subtle reduction in the packing parameter, which in turn induces either vesicle-to-worm or worm-to-sphere transitions...
September 21, 2017: Polymer Chemistry
https://www.readbyqxmd.com/read/29306572/novel-biotin-linker-with-alkyne-and-amino-groups-for-chemical-labelling-of-a-target-protein-of-a-bioactive-small-molecule
#6
Tomoaki Anabuki, Miu Tsukahara, Masanori Okamoto, Hideyuki Matsuura, Kosaku Takahashi
We synthesized a novel linker (1) with biotin, alkyne and amino groups for the identification of target proteins using a small molecule that contains an azide group (azide probe). The alkyne in the linker bound the azide probe via an azide-alkyne Huisgen cycloaddition. A protein cross-linker effectively bound the conjugate of the linker and an azide probe with a target protein. The covalently bound complex was detected by western blotting. Linker 1 was applied to a model system using an abscisic acid receptor, RCAR/PYR/PYL (PYL)...
December 26, 2017: Bioorganic & Medicinal Chemistry Letters
https://www.readbyqxmd.com/read/29286378/combining-chemical-cross-linking-and-mass-spectrometry-of-intact-protein-complexes-to-study-the-architecture-of-multi-subunit-protein-assemblies
#7
Caroline Haupt, Tommy Hofmann, Sabine Wittig, Susann Kostmann, Argyris Politis, Carla Schmidt
Proteins interact with their ligands to form active and dynamic assemblies which carry out various cellular functions. Elucidating these interactions is therefore fundamental for the understanding of cellular processes. However, many protein complexes are dynamic assemblies and are not accessible by conventional structural techniques. Mass spectrometry contributes to the structural investigation of these assemblies, and particularly the combination of various mass spectrometric techniques delivers valuable insights into their structural arrangement...
November 28, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/29280383/engineering-of-%C3%AE-hydroxyl-esters-into-elastomer-nanoparticle-interface-towards-malleable-robust-and-reprocessable-vitrimer-composites
#8
Yingjun Liu, Zhenghai Tang, Yi Chen, Chengfeng Zhang, Baochun Guo
Rubbers are strategically important due to their indispensable applications in the daily life and high-tech fields. For their real-world applications, the covalent cross-linking, reinforcement, and malleability of rubbers are three important issues because they are closely related to the elasticity, mechanical properties and recycling of the rubber materials. Herein, we demonstrate a simple way to prepare covalently cross-linked yet recyclable, and robust elastomeric vitrimer composites by incorporating exchangeable β-hydroxyl ester bonds into elastomer-nanoparticle interface using epoxy group-functionalized silica (Esilica) as both cross-linker and reinforcement in carboxyl group-grafted styrene-butadiene rubber (CSBR)...
December 27, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29240412/integration-of-on-column-chemical-reactions-in-protein-characterization-by-lc-ms-cross-path-reactive-chromatography
#9
Jake Pawlowski, Ian Carrick, Igor A Kaltashov
Profiling of complex proteins by means of mass spectrometry (MS) frequently requires that certain chemical modifications of their covalent structure (e.g., reduction of disulfide bonds) be carried out prior to the MS or MS/MS analysis. Traditionally, these chemical reactions take place in the off-line mode to allow the excess reagents (the majority of which interfere with the MS measurements and degrade the analytical signal) to be removed from the protein solution prior to MS measurements. In addition to a significant increase in the analysis time, chemical reactions may result in a partial or full loss of the protein if the modifications adversely affect its stability, e...
December 14, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/29235511/production-of-lignin-based-insoluble-polymers-anionic-hydrogels-by-c-versicolor
#10
Ivana Brzonova, Evguenii I Kozliak, Anastasia A Andrianova, Audrey LaVallie, Alena Kubátová, Yun Ji
Unlike previous lignin biodegradation studies, white rot fungi were used to produce functional biopolymers from Kraft lignin. Lignin-based polymers (hydrogel precursors) partially soluble in both aqueous and organic solvents were produced employing a relatively fast (6 days) enzymation of Kraft lignin with basidiomycetes, primarily Coriolus versicolor, pre-grown on kenaf/lignin agar followed by either vacuum evaporation or acid precipitation. After drying followed by a treatment with alkaline water, this intermediate polymer became a pH-sensitive anionic hydrogel insoluble in either aqueous or organic solvents...
December 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29229527/surface-proteins-and-the-formation-of-biofilms-by-staphylococcus-aureus
#11
Sung Joon Kim, James Chang, Binayak Rimal, Hao Yang, Jacob Schaefer
Staphylococcus aureus biofilms pose a serious clinical threat as reservoirs for persistent infections. Despite this clinical significance, the composition and mechanism of formation of S. aureus biofilms are unknown. To address these problems, we used solid-state NMR to examine S. aureus (SA113), a strong biofilm-forming strain. We labeled whole cells and cell walls of planktonic cells, young biofilms formed for 12-24h after stationary phase, and more mature biofilms formed for up to 60h after stationary phase...
December 8, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/29226612/glutaraldehyde-cross-linking-increases-the-stability-of-lumbricus-terrestris-erythrocruorin
#12
Athul Rajesh, Devon Zimmerman, Kyle Spivack, Osheiza Abdulmalik, Jacob Elmer
Since donated red blood cells must be constantly refrigerated, they are not available in remote areas and battlefields. We have previously shown that the hemoglobin of the earthworm Lumbricus terrestris (LtEc) is an effective and safe substitute for donated blood that is stable enough to be stored for long periods at the relatively high temperatures that may be encountered in remote areas. The goal of this study was to increase the thermal stability of LtEc by covalently cross-linking LtEc with glutaraldehyde (gLtEc)...
December 11, 2017: Biotechnology Progress
https://www.readbyqxmd.com/read/29205113/immobilization-techniques-applied-to-the-development-of-biocatalysts-for-the-synthesis-of-nucleoside-analogue-derivatives
#13
Jorge Abel Trelles, Maria Jose Lapponiab
BACKGROUND: Nucleoside analogue (NAs) derivatives comprise a large family of pharmaceuticals clinically used as antitumoral and antiviral compounds. Originally, the production of NAs involved chemical synthesis, but a greener bioproduction alternative exists and involves the use of enzymes that catalyze transglycosylation reactions between modified purinic or pyrimidinic bases and sugars. To be considered as an option for industrial application, it is vital to immobilize these biocatalysts...
December 3, 2017: Current Pharmaceutical Design
https://www.readbyqxmd.com/read/29202281/structure-and-properties-of-epoxy-siloxane-silica-nanocomposite-coatings-for-corrosion-protection
#14
Ruben F A O Torrico, Samarah V Harb, Andressa Trentin, Mayara C Uvida, Sandra H Pulcinelli, Celso V Santilli, Peter Hammer
HYPOTHESIS: The fraction of the silica/siloxane phase is a crucial parameter, which determines the structure and thus the properties of epoxy-siloxane-silica hybrid coatings. A careful adjustment of the colloidal precursor formulation allows tuning the nanostructure towards a highly condensed and cross-linked hybrid nanocomposite, suitable as an efficient anticorrosive coating. EXPERIMENTS: Novel epoxy-siloxane-silica hybrids have been prepared through the curing reaction of poly(bisphenol A-co-epichlorohydrin) (DGEBA) with diethyltriamine (DETA) and (3-glycidoxypropyl)methyltriethoxysilane (GPTMS), followed by hydrolytic condensation of tetraethoxysilane (TEOS) and GPTMS...
November 24, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/29202224/mussel-inspired-self-healing-double-cross-link-hydrogels-by-controlled-combination-of-metal-coordination-and-covalent-cross-linking
#15
Amanda Andersen, Marie Krogsgaard, Henrik Birkedal
Mussel-inspired hydrogels held together by reversible catecholato-metal coordination bonds have recently drawn great attention owing to their attractive self-healing, viscoelastic and adhesive properties together with their pH-responsive nature. A major challenge in these systems is to orchestrate the degree of catechol oxidation that occurs under alkaline conditions in air and has a great impact on the aforementioned properties because it introduces irreversible covalent cross-links to the system, which stiffens the hydrogels but consume catechols needed for self-healing...
December 4, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/29198943/human-bile-acid-transporter-asbt-slc10a2-forms-functional-non-covalent-homodimers-and-higher-order-oligomers
#16
Paresh P Chothe, Lindsay C Czuba, Robyn H Moore, Peter W Swaan
The human apical sodium-dependent bile acid transporter, hASBT/SLC10A2, plays a central role in cholesterol homeostasis via the efficient reabsorption of bile acids from the distal ileum. hASBT has been shown to self-associate in higher order complexes, but while the functional role of endogenous cysteines has been reported, their implication in the oligomerization of hASBT remains unresolved. Here, we determined the self-association architecture of hASBT by site-directed mutagenesis combined with biochemical, immunological and functional approaches...
November 30, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/29198120/in-situ-interfacial-conjugation-of-chitosan-with-cinnamaldehyde-during-homogenization-improves-the-formation-and-stability-of-chitosan-stabilized-emulsions
#17
Huanle Chen, David Julian McClements, Enmin Chen, Shilin Liu, Bin Li, Yan Li
The emulsifying properties of a natural cationic polysaccharide (chitosan) were improved by in situ conjugation with a natural essential oil (cinnamaldehyde, CA) during homogenization. In the absence of CA, chitosan-coated medium chain triglyceride (MCT) droplets were highly susceptible to creaming and coalescence at pH values ranging from 1 to 6.5. However, incorporation of relatively low levels of CA in the oil phase greatly improved the formation and stability of the oil-in-water emulsions. These effects were attributed to two main factors: (i) covalent binding of lipophilic CA moieties to hydrophilic chitosan chains leading to conjugates with good surface-activity; (ii) interfacial cross-linking of adsorbed chitosan layers by CA leading to the formation of a rigid polymeric coating around the lipid droplets that improved their stability against coalescence...
December 4, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29193844/sodium-bicarbonate-gelled-chitosan-beads-as-mechanically-stable-carriers-for-the-covalent-immobilization-of-enzymes
#18
Marwa I Wahba
The poor mechanical stability of chitosan has long impeded its industrial utilization as an immobilization carrier. In this study, the mechanical properties of chitosan beads were greatly improved through utilizing the slow rate of the sodium bicarbonate-induced chitosan gelation and combining it with the chemical cross-linking action of glutaraldehyde (GA). The GA-treated sodium bicarbonate-gelled chitosan beads exhibited much better mechanical properties and up to 2.45-fold higher observed activity of the immobilized enzyme (β-D-galactosidase (β-gal)) when compared to the GA-treated sodium tripolyphosphate (TPP)-gelled chitosan beads...
November 29, 2017: Biotechnology Progress
https://www.readbyqxmd.com/read/29180686/immobilized-cerrena-sp-laccase-preparation-thermal-inactivation-and-operational-stability-in-malachite-green-decolorization
#19
Jie Yang, Zhengjuan Wang, Yonghui Lin, Tzi Bun Ng, Xiuyun Ye, Juan Lin
Laccases are polyphenol oxidases with widespread applications in various industries. In the present study, the laccase from Cerrena sp. HYB07 was immobilized with four methods, namely entrapment in alginate, covalently binding to chitosan as well as formation of cross-linked enzyme aggregates (CLEAs) and magnetic CLEAs (M-CLEAs). The activity recovery rates of the immobilized laccases ranged from 29% to 68%. Immobilization elevated the reaction temperature optimum and reduced substrate specificity, but not necessarily the turnover rate...
November 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29178472/enzymatic-degradation-of-hyaluronan-hydrogels-with-different-capacity-for-in-situ-bio-mineralization
#20
Liyang Shi, Yu Zhang, Dmitri Ossipov
In situ cross-linked hyaluronan (HA) hydrogels with different capacities for biomineralization were prepared and their enzymatic degradation was monitored. Covalent incorporation of bisphosphonates (BPs) into HA hydrogel results in the increased stiffness of the hydrogel in comparison with the unmodified HA hydrogel of the same cross-linking density. The rate of enzymatic degradation of HABP hydrogel was significantly lower than the rate of degradation of control HA hydrogel in vitro. This effect is observed only in the presence of calcium ions that strongly bind to the matrix-anchored BP groups and promote further mineralization of the matrix...
November 27, 2017: Biopolymers
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