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Covalently cross linked

Maryam Khan, Qayyum Husain, Rani Bushra
The present study aimed to work out a high yield procedure for immobilization of Aspergillus oryzae β-galactosidase on polyaniline cobalt multiwalled carbon nanotubes nanocomposite (PANI/Co/MWCNTNC) by physical adsorption and covalent attachment via glutaraldehyde. The binding was confirmed by scanning and transmission electron microscopy along with Fourier transform-infrared spectroscopy. The immobilization yields obtained for adsorbed and cross-linked enzymes were 93% and 97%, respectively. The covalently immobilized enzyme was remarkably more stable at extremes of pH and temperature compared to native and adsorbed enzymes...
July 19, 2017: International Journal of Biological Macromolecules
Marwa I Wahba
Porous chitosan beads of superior mechanical properties were produced via a two stepped treatment process. First, the chitosan ionotropic gelation solution was supplemented with Na2CO3, which acted as a porogen. Afterwards, the beads were chemically cross-linked with glutaraldehyde. This treatment also caused the produced porous chitosan beads to acquire higher observed activities of immobilized β-D-galactosidase (β-gal). The observed activities of the β-gal immobilized onto the 0.2M and the 0.35M Na2CO3 treated beads were 1...
July 18, 2017: International Journal of Biological Macromolecules
Yifan Dai, Alireza Molazemhosseini, Chung Chiun Liu
A simple in vitro biosensor for the detection of β-amyloid 42 in phosphate-buffered saline (PBS) and undiluted human serum was fabricated and tested based on our platform sensor technology. The bio-recognition mechanism of this biosensor was based on the effect of the interaction between antibody and antigen of β-amyloid 42 to the redox couple probe of K₄Fe(CN)₆ and K₃Fe(CN)₆. Differential pulse voltammetry (DPV) served as the transduction mechanism measuring the current output derived from the redox coupling reaction...
July 20, 2017: Biosensors
Yu G Maksimova, A N Gorbunova, V A Demakov
We studied the effect of a heterogeneous environment on the stereoselectivity of transformation of racemic phenylglycine nitrile. Immobilized biocatalysts were prepared by adhesion of Pseudomonas fluorescens C2 cells on carbon-containing supports and covalent crosslinking of nitrile hydratase and amidase of Rhodococcus rhodochrous 4-1 to activated chitosan as well as by the method of cross-linked aggregates. At a reaction duration of 20 h, the ratio of phenylglycine stereoisomers changes depending on the presence of support in medium...
May 2017: Doklady. Biochemistry and Biophysics
Willem Vannecke, Christophe Ampe, Marleen Van Troys, Massimiliano Beltramo, Annemieke Madder
Chemical cross-linking is well-established for investigating protein-protein interactions. Traditionally, photo cross-linking is used but is associated with problems of selectivity and UV toxicity in a biological context. We here describe, with live cells and under normal growth conditions, selective cross-linking of a furan-modified peptide ligand to its membrane-presented receptor with zero toxicity, high efficiency, and spatio-specificity. Furan-modified kisspeptin-10 is covalently coupled to its glycosylated membrane receptor, GPR54(KISS1R)...
July 17, 2017: ACS Chemical Biology
Y Gilad, H Tuchinsky, G Ben-David, R Minnes, A Gancz, H Senderowitz, G Luboshits, M A Firer, G Gellerman
The resistance of cancer cells to chemotherapeutic agents, whether through intrinsic mechanisms or developed resistance, motivates the search for new chemotherapeutic strategies. In the present report, we demonstrate a facile synthetic strategy towards the discovery of new anti-cancer substances. This strategy is based on simple covalent coupling between known anti-cancer drugs, which results in novel 'chimeric' small molecules. One of these novel compounds, CM358, is the product of an amide bond formation between the known Topoisomerase II (Topo II) inhibitor amonafide (AM) and the known DNA mustard alkylator chlorambucil (CLB)...
June 29, 2017: European Journal of Medicinal Chemistry
Roya Biabanikhankahdani, Saadi Bayat, Kok Lian Ho, Noorjahan Banu Mohamed Alitheen, Wen Siang Tan
pH-responsive virus-like nanoparticles (VLNPs) hold promising potential as drug delivery systems for cancer therapy. In the present study, hepatitis B virus (HBV) VLNPs harbouring His-tags were used to display doxorubicin (DOX) via nitrilotriacetic acid (NTA) conjugation. The His-tags served as pH-responsive nanojoints which released DOX from VLNPs in a controlled manner. The His-tagged VLNPs conjugated non-covalently with NTA-DOX, and cross-linked with folic acid (FA) were able to specifically target and deliver the DOX into ovarian cancer cells via folate receptor (FR)-mediated endocytosis...
July 13, 2017: Scientific Reports
Ivana Mižíková, Francesco Palumbo, Tamás Tábi, Susanne Herold, István Vadász, Konstantin Mayer, Werner Seeger, Rory E Morty
Lysyl oxidases are credited with pathogenic roles in lung diseases, including cancer, fibrosis, pulmonary hypertension, congenital diaphragmatic hernia, and bronchopulmonary dysplasia (BPD). Lysyl oxidases facilitate the covalent intra- and inter-molecular cross-linking of collagen and elastin fibers, thereby imparting tensile strength to the extracellular matrix (ECM). Alternative ECM-independent roles have recently been proposed for lysyl oxidases, including regulation of growth factor signaling, chromatin remodeling, and transcriptional regulation; all of which impact cell phenotype...
July 10, 2017: Physiological Genomics
Jorge A Marquez-Escalante, Elizabeth Carvjal-Millan, Madhav P Yadav, Madhuvanti Kale, Agustín Rascon-Chu, Alfonso A Gardea, Elisa Valenzuela-Soto, Yolanda L Lopez-Franco, Jaime Lizardi-Mendoza, Craig B Faulds
BACKGROUND: Arabinoxylans (AX) are polysaccharides constituted by a backbone of xyloses with arabinose substituents ester-linked to ferulic acid (FA). The arabinose to xylose ratio (A/X) in AX may vary from 0.3 to 1.1. AX form covalent gels by cross-linking of FA but physical interactions between AX chains also contribute to the network formation. The objective of this study was to investigate the rheological and microstructural characteristics of gels based on AX enzymatically modified in A/X...
July 11, 2017: Journal of the Science of Food and Agriculture
Tomasz Jóźwiak, Urszula Filipkowska, Paula Szymczyk, Małgorzata Kuczajowska-Zadrożna, Artur Mielcarek
A hydrogel chitosan sorbent ionically cross-linked with sodium citrate and covalently cross-linked with epichlorohydrin was used to remove nutrients from an equimolar mixture of P-PO4, N-NO2 and N-NO3. The scope of the study included, among other things, determination of the influence of pH on nutrient sorption effectiveness, nutrient sorption kinetics as well as determination of the maximum sorption capacity of cross-linked chitosan sorbents regarding P-PO4 (H2PO4(-), HPO4(2-)), N-NO2 (HNO2, NO2(-)), and N-NO3 (NO3(-))...
July 4, 2017: International Journal of Biological Macromolecules
Jun Yang, Feng Xu
Engineering reversible cross-links between nanoparticles and polymer matrix is a promising avenue to reinforce the mechanical properties of elastomers and in particular soft hydrogels. In this work, we study a model system of composite hydrogel reinforced with cellulose nanofibrils (CNFs), where the integration of reversible hydrogen bonds into a lightly covalently cross-linked polyacrylamide (PAAm) matrix. This approach yields the dual cross-linked networks with synergistically improved strength, modulus, and toughness...
July 18, 2017: Biomacromolecules
Claudia Loebel, Christopher B Rodell, Minna H Chen, Jason A Burdick
The design of injectable hydrogel systems addresses the growing demand for minimally invasive approaches for local and sustained delivery of therapeutics. We developed a class of hyaluronic acid (HA) hydrogels that form through noncovalent guest-host interactions, undergo disassembly (shear-thinning) when injected through a syringe and then reassemble within seconds (self-healing) when shear forces are removed. Its unique properties enable the use of this hydrogel system for numerous applications, such as injection in vivo (including with cells and therapeutic molecules) or as a 'bioink' in 3D-printing applications...
August 2017: Nature Protocols
Hong Ni, Feiyu Xu, Antoni P Tomsia, Eduardo Saiz, Lei Jiang, Qunfeng Cheng
Graphene composite films inspired by nacre are the subject of ongoing research efforts to optimize their properties for applications in flexible energy devices. Noncovalent interactions do not cause interruption of the delocalized conjugated π-electron system, thus preserving graphene's excellent properties. Herein, we synthesized a conjugated molecule with pyrene groups on both ends of a long linear chain (AP-DSS) from 1-aminopyrene (AP) and disuccinimidyl suberate (DSS). The AP-DSS molecules are used to cross-link adjacent graphene nanosheets via π-π interfacial interactions to improve properties of graphene films...
July 17, 2017: ACS Applied Materials & Interfaces
Horacio L Bonazza, Ricardo M Manzo, José C S Dos Santos, Enrique J Mammarella
The aim of this paper was to evaluate different strategies of chitosan activation using cross-linking reagent like glycidol, epichlorohydrin, and glutaraldehyde for Thermomyces lanuginosus lipase (TLL) immobilization. Operational activity and stability by esterification of oleic acid with ethanol and thermal inactivation using these derivatives were investigated. Derivative obtained by sequentially activation with glycidol, ethylenediamine, and glutaraldehyde and subsequent TLL immobilization showed the best performance, with high hydrolytic activity value...
June 29, 2017: Applied Biochemistry and Biotechnology
Kevin S Hof, Maartje M C Bastings
The extracellular matrix (ECM) and cells have a reciprocal relationship, one shapes the other and vice versa. One of the main challenges of synthetic material systems for developmental cell culturing, organoid and stem cell work includes the implementation of this reciprocal nature. The largest hurdle to achieve true cell-instructive materials in biomaterials engineering is a lack of spatial and temporal control over material properties and the display of bioactive signals compared to the natural cell environment...
June 28, 2017: Chimia
Süleyman Cinar, Claus Czeslik
Responsive interfaces are often realized by polymer films that change their structure and properties upon changing the pH-value, ionic strength or temperature. Here, we present a bioresponsive interfacial structure that is based on a protein, calmodulin (CaM), which undergoes a huge conformational change upon ligand binding. At first, we characterize the conformational functionality of a double Cys mutant of CaM by small-angle X-ray scattering (SAXS) and Fourier transform infrared (FTIR) spectroscopy. The CaM mutant is then used to cross-link poly(ethylene glycol) (PEG) chains, which are bound covalently to a supporting planar Si surface...
June 21, 2017: Colloids and Surfaces. B, Biointerfaces
Alejandra Castaño, Upasana Roy, Orlando D Schärer
Nitrogen mustards (NMs) react with two bases on opposite strands of a DNA duplex to form a covalent linkage, yielding adducts called DNA interstrand cross-links (ICLs). This prevents helix unwinding, blocking essential processes such as replication and transcription. Accumulation of ICLs causes cell death in rapidly dividing cells, especially cancer cells, making ICL-forming agents like NMs valuable in chemotherapy. However, the repair of ICLs can contribute to chemoresistance through a number of pathways that remain poorly understood...
2017: Methods in Enzymology
Cesare Benedetti, Paraskevi Flouda, Alice Antonello, Christine Rosenauer, Francisco F Perez-Pla, Katharina Landfester, Silvia Gross, Rafael Munoz-Espi
Photoactivated free radical miniemulsion copolymerization of methyl methacrylate (MMA) and the zirconium oxocluster Zr4O2(methacrylate)12 is used as an effective and fast preparation method of polymer/inorganic hybrid nanoparticles. The oxoclusters, covalently anchored to the polymer network, act as metal-organic cross-linkers, thus improving the thermomechanical properties of the resulting hybrid nanoparticles. Benzoin carbonyl organic compounds were used as photoinitiators. The obtained materials are compared in terms of cross-linking, effectiveness of cluster incorporation, and size distribution with the analogous nanoparticles produced by using conventional thermally-induced free radical miniemulsion copolymerization...
June 23, 2017: Nanotechnology
Mohammad Ali Darabi, Ali Khosrozadeh, Rene Mbeleck, Yuqing Liu, Qiang Chang, Junzi Jiang, Jun Cai, Quan Wang, Gaoxing Luo, Malcolm Xing
The advent of conductive self-healing (CSH) hydrogels, a class of novel materials mimicking human skin, may change the trajectory of the industrial process because of their potential applications in soft robots, biomimetic prostheses, and health-monitoring systems. Here, the development of a mechanically and electrically self-healing hydrogel based on physically and chemically cross-linked networks is reported. The autonomous intrinsic self-healing of the hydrogel is attained through dynamic ionic interactions between carboxylic groups of poly(acrylic acid) and ferric ions...
June 22, 2017: Advanced Materials
Chong-Feng Xu, Yunqiu Chen, Linda Yi, Tim Brantley, Brad Stanley, Zoran Sosic, Li Zang
Novel cross-links between an oxidized histidine and intact histidine, lysine, or cysteine residues were discovered and characterized from high-molecular weight (HMW) fractions of an IgG1 monoclonal antibody (mAb). The mAb HMW fractions were collected using preparative size-exclusion chromatography (SEC) and extensively characterized to understand the mechanism of formation of the nonreducible and covalently linked portion of the HMWs. The HMW fractions were IdeS digested, reduced, and analyzed by size-exclusion chromatography coupled with mass spectrometry (SEC-MS)...
July 10, 2017: Analytical Chemistry
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