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Covalently cross linked

Cayla Baynes, Jeong-Yeol Yoon
A microfluidic paper analytical device (μPAD) was created for the sensitive quantification of cancer antigens, carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA 19-9), from human whole blood and serum, toward diagnosis and prognosis of colorectal cancer. Anti-CEA and anti-CA 19-9 antibodies were covalently linked to submicron, fluorescent polystyrene particles, loaded, and then dried in the center of the μPAD channel. CEA- or CA 19-9-spiked blood or serum samples were loaded to the inlet of μPAD, and subsequent immunoagglutination changed the fluorescent scatter signals upon ultraviolet (UV) excitation...
September 1, 2017: SLAS Technology
Vivian Müller, Feng Shao, Milos Baljozovic, Mina Moradi, Yao Zhang, Thomas Jung, William B Thompson, Benjamin T King, Renato Zenobi, A Dieter Schlüter
This work describes a two-dimensional polymerization at an air/water interface and provides, for the first time, direct spectroscopic evidence for the kind of cross-links formed and for the conversion reached in a covalently bonded monolayer sheet. This is achieved by a combination of a variety of monolayer characterization techniques before and after transfer onto solid substrates in particular by tip-enhanced Raman spectroscopy (TERS) and TERS mapping after transfer of both the monomer and polymer monolayer onto Au(111)...
September 18, 2017: Angewandte Chemie
Matthew J Schellenberg, Jenna Ariel Lieberman, Andrés Herrero-Ruiz, Logan R Butler, Jason G Williams, Ana M Muñoz-Cabello, Geoffrey A Mueller, Robert E London, Felipe Cortés-Ledesma, R Scott Williams
Topoisomerase 2 (TOP2) DNA transactions are essential for life, and proceed via formation of the TOP2 cleavage complex (TOP2cc), a covalent enzyme-DNA reaction intermediate that is vulnerable to trapping by potent anticancer TOP2 drugs. How genotoxic TOP2 DNA-protein cross-links are resolved is unclear. We found that the SUMO ligase ZATT (ZNF451) is a multifunctional DNA repair factor that controls cellular responses to TOP2 damage. ZATT binding to TOP2cc facilitates a proteasome-independent tyrosyl-DNA phosphodiesterase 2 (TDP2) hydrolase activity on stalled TOP2cc...
September 14, 2017: Science
Shaofei Ji, Hongzhao Shao, Qiyuan Han, Christopher L Seiler, Natalia Tretyakova
5-Formylcytosine (5fC) is an endogenous DNA modification frequently found within regulatory elements of mammalian genes. Although 5fC is an oxidation product of 5-methylcytosine (5mC), the two epigenetic marks show distinct genome-wide distributions and protein affinities, suggesting that they perform different functions in epigenetic signaling. A unique feature of 5fC is the presence of a potentially reactive aldehyde group in its structure. Here, we show that 5fC bases in DNA readily form Schiff base conjugates with Lys side chains of nuclear proteins in vitro and in vivo...
September 12, 2017: Angewandte Chemie
Jerzy Karpiuk, Alina Majka, Ewelina Karolak, Jacek Nowacki
In frozen solvents at 77 K, ultrafast (≤ 250 fs) photoinduced intramolecular electron transfer (ET) in bichromophoric donor-acceptor ([D-A]) diarylmethane lactones produces a covalently linked radical ion pair, 1[D•+-A•-]. Steady state and time-resolved luminescence measurements reveal that 1[D•+-A•-] decays to charge-separated (3[D•+-A•-]) and donor-centered ([3D*-A]) triplets, which display dual phosphorescence. 3[D•+-A•-] and [3D*-A] are formed in parallel via two intersystem crossing mechanisms: spin orbit charge transfer (SOCT) and hyperfine coupling (HFC), with solvent dependent branching ratio...
September 11, 2017: Journal of Physical Chemistry Letters
Mingchuan Yu, Hanmin Zhang, Fenglin Yang
Forward osmosis (FO) technology is an efficient route to obtain purity water for drinking from wastewater or seawater. However, there are some challenges in draw solution to limit its application. We firstly introduce a novel sodium alginate-graphene oxide (SA-GO) aerogel as draw agent for highly efficient FO process. The GO nanosheets covalently cross-linked to SA matrix to form a three-dimensional and highly porous aerogel to provide excellent water flux and operation stability, together with the property of compressibility served by SA-GO aerogel resulting in easy water production and regeneration process...
September 11, 2017: ACS Applied Materials & Interfaces
Richard B Cooley, Holger Sondermann
Fundamental to all living organisms is the ability of proteins to interact with other biological molecules at the right time and location, with the proper affinity, and to do so reversibly. One well-established technique to study protein interactions is chemical cross-linking, a process in which proteins in close spatial proximity are covalently tethered together. An emerging technology that overcomes many limitations of traditional cross-linking methods is one in which photoactivatable cross-linking noncanonical amino acids are genetically encoded into a protein of interest using the cell's native translational machinery...
2017: Methods in Molecular Biology
Shingi Yamaguchi, Kazuhide Kamiya, Kazuhito Hashimoto, Shuji Nakanishi
This work demonstrates that a single Ru atom-modified covalent triazine framework (Ru-CTF) has selectivity for the electrooxidation of benzyl alcohol in water over the oxygen evolution reaction. Additionally, Ru-CTF displayed higher stability than an immobilized Ru-organometallic complex due to the covalently cross-linked structure of CTF.
September 25, 2017: Chemical Communications: Chem Comm
Mark P Hendricks, Kohei Sato, Liam C Palmer, Samuel I Stupp
Peptide amphiphiles (PAs) are small molecules that contain hydrophobic components covalently conjugated to peptides. In this Account, we describe recent advances involving PAs that consist of a short peptide sequence linked to an aliphatic tail. The peptide sequence can be designed to form β-sheets among the amino acids near the alkyl tail, while the residues farthest from the tail are charged to promote solubility and in some cases contain a bioactive sequence. In water, β-sheet formation and hydrophobic collapse of the aliphatic tails induce assembly of the molecules into supramolecular one-dimensional nanostructures, commonly high-aspect-ratio cylindrical or ribbonlike nanofibers...
September 6, 2017: Accounts of Chemical Research
Jie Long, Bao Zhang, Xingfei Li, Xiaobei Zhan, Xueming Xu, Zhengjun Xie, Zhengyu Jin
In this study, pullulanase was firstly immobilized by covalent bonding onto chitosan/Fe3O4 nanoparticles or encapsulation in sol-gel after bonding onto chitosan/Fe3O4 nanoparticles, and then the immobilized pullulanase was used for the effective production of resistant starch (RS). The highest RS content (35.1%) was obtained under the optimized condition of pH 4.4, enzyme concentration of 10ASPU/g and hydrolysis time of 12h when debranched by free pullulsanase, indicating that RS content was significantly (p<0...
January 15, 2018: Food Chemistry
Nina B Hentzen, Linde E J Smeenk, Jagna Witek, Sereina Riniker, Helma Wennemers
Covalent cross-links are crucial for the folding and stability of triple-helical collagen, the most abundant protein in nature. Cross-linking is also an attractive strategy for the development of synthetic collagen-based biocompatible materials. Nature uses interchain disulfide bridges to stabilize collagen trimers. However, their implementation into synthetic collagen is difficult and requires the replacement of the canonical amino acids (4R)-hydroxyproline and proline by cysteine or homocysteine, which reduces the preorganization and thereby stability of collagen triple helices...
September 5, 2017: Journal of the American Chemical Society
Xian-Fu Zhang, Xudong Yang, Baomin Xu
Herein, four covalent BODIPY heterodimers that differ by dihedral angles were shown to be highly efficient excited triplet state (T1) photosensitizers (PSs) for singlet oxygen formation with a quantum yield (ΦΔ) of up to 0.94 as compared to their respective monomers, which had only negligible ΦΔ of ca. 0.060. More interestingly, these PSs generate T1via charge recombination mechanism rather than traditional inter-system crossing. The photosensitizing ability of dimers is easily tuned by either the dihedral angle (between the two linked BODIPYs) or solvent polarity...
September 20, 2017: Physical Chemistry Chemical Physics: PCCP
Savannah Afsahi, Mitchell B Lerner, Jason M Goldstein, Joo Lee, Xiaoling Tang, Dennis A Bagarozzi, Deng Pan, Lauren Locascio, Amy Walker, Francie Barron, Brett R Goldsmith
We have developed a cost-effective and portable graphene-enabled biosensor to detect Zika virus with a highly specific immobilized monoclonal antibody. Field Effect Biosensing (FEB) with monoclonal antibodies covalently linked to graphene enables real-time, quantitative detection of native Zika viral (ZIKV) antigens. The percent change in capacitance in response to doses of antigen (ZIKV NS1) coincides with levels of clinical significance with detection of antigen in buffer at concentrations as low as 450pM...
August 24, 2017: Biosensors & Bioelectronics
Artur Kaczmarczyk, Abdollah Allahverdi, Thomas B Brouwer, Lars Nordenskiöld, Nynke H Dekker, John van Noort
The eukaryotic genome is highly compacted into a protein-DNA complex called chromatin. The cell controls access of transcriptional regulators to chromosomal DNA via several mechanisms that act on chromatin-associated proteins and provide a rich spectrum of epigenetic regulation. Elucidating the mechanisms that fold chromatin fibers into higher-order structures is therefore key to understanding the epigenetic regulation of DNA accessibility. Here, using histone H4-V21C and histone H2A-E64C mutations, we employed single-molecule force spectroscopy to measure the unfolding of individual chromatin fibers that are reversibly cross-linked through the histone H4 tail...
August 30, 2017: Journal of Biological Chemistry
Yanny Marliana Baba Ismail, Ana Marina Ferreira, Oana Bretcanu, Kenneth Dalgarno, Alicia J El Haj
This paper presents a new approach in assembling bone extracellular matrix components onto PLA films, and investigates the most favourable environment which can be created using the technique for cell-material interactions. Poly (lactic acid) (PLA) films were chemically modified by covalently binding the poly(ethylene imine) (PEI) as to prepare the substrate for immobilization of polyelectrolyte multilayers (PEMs) coating. Negatively charged polyelectrolyte consists of well-dispersed silicon-carbonated hydroxyapatite (SiCHA) nanopowders in hyaluronic acid (Hya) was deposited onto the modified PLA films followed by SiCHA in collagen type I as the positively charged polyelectrolyte...
August 14, 2017: Colloids and Surfaces. B, Biointerfaces
Jing Fu, Paul A Guerette, Andrea Pavesi, Nils Horbelt, Chwee Teck Lim, Matthew J Harrington, Ali Miserez
Stiff fibers are used as reinforcing phases in a wide range of high-performance composite materials. Silk is one of the most widely studied bio-fibers, but alternative materials with specific advantages are also being explored. Among these, native hagfish (Eptatretus stoutii) slime thread is an attractive protein-based polymer. These threads consist of coiled-coil intermediate filaments (IFs) as nano-scale building blocks, which can be transformed into extended β-sheet-containing chains upon draw-processing, resulting in fibers with impressive mechanical performance...
September 14, 2017: Nanoscale
Matthew T Mawhinney, Thomas L Williams, James L Hart, Mitra L Taheri, Brigita Urbanc
Deficiency in insulin secretion and function that characterize type 2 diabetes often requires administration of extraneous insulin, leading to injection-site amyloidosis. Insulin aggregation at neutral pH is not well understood. Although oligomer formation is believed to play an important role, insulin oligomers have not been fully characterized yet. Here, we elucidate similarities and differences between in vitro insulin aggregation at acidic and neutral pH for a range of insulin concentrations (2.5-100 μM) by using kinetic thioflavin T fluorescence, circular dichroism, atomic force and electron microscopy imaging...
August 10, 2017: Proteins
K Wilma, T Unger, S Tuncel Kostakoğlu, M Hollfelder, C Hunger, A Lang, A G Gürek, M Thelakkat, J Köhler, A Köhler, S Gekle, R Hildner
We investigate the excited state dynamics and the conformations of a new molecular donor-bridge-acceptor system, a Cu(ii)-phthalocyanine (CuPc) covalently linked via a flexible aliphatic spacer to a perylenebisimide (PBI). We performed time-resolved polarization anisotropy and pump-probe measurements in combination with molecular dynamics simulations. Our data suggest the existence of three conformations of the dyad: two more extended, metastable conformations with centre-of-mass distances >1 nm between the PBI and CuPc units of the dyad, and a highly stable folded structure, in which the PBI and CuPc units are stacked on top of each other with a centre-of-mass distance of 0...
August 23, 2017: Physical Chemistry Chemical Physics: PCCP
C N R Rao, K Pramoda, Ram Kumar
Covalent linking of 2D structures such as graphene, MoS2 and C3N4 by employing coupling reactions provides a strategy to generate a variety of materials with new or improved properties. These materials in a way provide the counter point based on covalent bonds to the van der Waals heterostructures. In this article, we describe materials obtained by linking graphene, MoS2 and BN with other layered structures and also with one-dimensional nanotubes and zero-dimensional MOFs and MOPs. Novel properties of the materials relate not only to porosity, surface area and gas adsorption, but also to supercapacitor characterstics, mechanical properties and the hydrogen evolution reaction...
August 10, 2017: Chemical Communications: Chem Comm
Hamid Maadi, Babak Nami, Zhixiang Wang
Dimerization of the epithelial growth factor (EGF) family of receptor tyrosine kinases is a crucial step for activation of these receptors. Different chemicals such as BS(3) and DSS have been introduced to covalently bind the interacting receptors and fix the dimers. Unique properties of BS(3) including higher water solubility and membrane impermeability make it suitable for assessing receptor-receptor interactions in live cells. In this protocol, we aim to explain a method to evaluate the dimerization of EGF receptors family using BS(3) as a cross-linker reagent...
2017: Methods in Molecular Biology
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