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https://www.readbyqxmd.com/read/30106067/naturally-occurring-quaternary-benzo-c-phenanthridine-alkaloids-selectively-stabilize-g-quadruplexes
#1
Petra Jarosova, Petr Paroulek, Michal Rajecky, Veronika Rajecka, Eva Taborska, Ramon Eritja, Anna Aviñó, Stefania Mazzini, Raimundo Gargallo, Petr Taborsky
In this work, the interaction of six natural benzo[c]phenanthridine alkaloids (macarpine, sanguilutine, sanguirubine, chelerythrine, sanguinarine and chelirubine) with parallel and antiparallel G-quadruplex DNA structures was studied. HT22 corresponding to the end of human telomeres and the modified promoter oncogene c-kit21 and Pu22 sequences have been used. Spectroscopically-monitored melting experiments and fluorescence titrations, competitive dialysis and nuclear magnetic resonance spectroscopy were used for this purpose...
August 14, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/30104563/single-molecule-detection-with-a-millimetre-sized-transistor
#2
Eleonora Macchia, Kyriaki Manoli, Brigitte Holzer, Cinzia Di Franco, Matteo Ghittorelli, Fabrizio Torricelli, Domenico Alberga, Giuseppe Felice Mangiatordi, Gerardo Palazzo, Gaetano Scamarcio, Luisa Torsi
Label-free single-molecule detection has been achieved so far by funnelling a large number of ligands into a sequence of single-binding events with few recognition elements host on nanometric transducers. Such approaches are inherently unable to sense a cue in a bulk milieu. Conceptualizing cells' ability to sense at the physical limit by means of highly-packed recognition elements, a millimetric sized field-effect-transistor is used to detect a single molecule. To this end, the gate is bio-functionalized with a self-assembled-monolayer of 1012 capturing anti-Immunoglobulin-G and is endowed with a hydrogen-bonding network enabling cooperative interactions...
August 13, 2018: Nature Communications
https://www.readbyqxmd.com/read/30091818/a-homoleptic-krf%C3%A2-complex-hg-krf%C3%A2-%C3%A2-asf%C3%A2-%C3%A2-%C3%A2-2hf
#3
John R DeBackere, Gary J Schrobilgen
The reaction of Hg(AsF₂)₂ with a large molar excess of KrF₂ in anhydrous HF has afforded the first homoleptic KrF₂ coordination complex, [Hg(KrF₂)₈][AsF₆]₂·2HF. The [Hg(KrF₂)₈]²+ dication is well-isolated in the low-temperature crystal structure of its HF-solvated [AsF₆]- salt, and consists of eight KrF₂ molecules that are terminally coordinated to Hg²+ by means of Hg-F(KrF) bonds to form a slightly distorted, square-antiprismaticic coordination sphere around mercury. The Raman spectrum of [Hg(KrF₂)₈]²+ was assigned with the aid of calculated gas-phase vibrational frequencies...
August 9, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30088850/mechanistic-investigation-into-dna-modification-by-a-ruii-rhiii-bimetallic-complex
#4
José Á Rodríguez-Corrales, Jing Wang, Brenda S J Winkel, Karen J Brewer
Despite significant progress in the treatment of cancer, there remains an urgent need for more effective therapies that also have less impact on patient wellbeing. Photodynamic therapy employs targeted light activation of a photosensitizer in selected tissues, thereby reducing off-target toxicity. Our group previously reported a RuII,RhIII bimetallic architecture that displays multifunctional covalent photomodification of DNA in the therapeutic window through an oxygen-independent manner, features essential for treating deep and hypoxic tumors...
August 8, 2018: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/30088765/tuning-the-redox-potentials-and-ligand-field-strength-of-fe-ii-polypyridines-the-dual-%C3%AF-donor-and-%C3%AF-acceptor-character-of-bipyridine
#5
Daniel C Ashley, Elena Jakubikova
The quintet-singlet energy difference (Δ EQ/S ) in Fe(II) polypyridine complexes is often interpreted in terms of metal-ligand π interactions. DFT calculations on a series of substituted [Fe(bpy)3 ]2+ (bpy = 2,2'-bipyridine) complexes show the disparate magnitudes of substituent effects on tuning Δ EQ/S and reduction potentials ( E°). In this series, E° spans a much larger range than Δ EQ/S (2.07 vs 0.29 eV). While small changes in Δ EQ/S are controlled by metal-ligand π interactions, large changes in E° arise from modification of the electrostatic environment around the Fe center...
August 8, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/30086184/two-mutations-at-different-positions-in-the-cnbh-domain-of-the-herg-channel-accelerate-deactivation-and-impair-the-interaction-with-the-eag-domain
#6
Shinichiro Kume, Takushi Shimomura, Michihiro Tateyama, Yoshihiro Kubo
KEY POINTS: In the hERG channel, both the EAG domain in the N-terminal and the CNBH domain in the C-terminal cytoplasmic region are known to contribute to the characteristic slow deactivation. Mutations of Phe860 in the CNBH domain, reported to fill the cyclic nucleotide (CN) binding pocket, accelerate the deactivation and decrease the FRET efficiencies between the EAG and CNBH domains. An electrostatic interaction between Arg696 and Asp727 in the C-linker domain, critical for HCN and CNG channels, is not formed in the hERG channel...
August 7, 2018: Journal of Physiology
https://www.readbyqxmd.com/read/30081466/kinetic-characterization-of-novel-hiv-1-entry-inhibitors-discovery-of-a-relationship-between-off-rate-and-potency
#7
Megan E Meuser, Michael B Murphy, Adel A Rashad, Simon Cocklin
The entry of HIV-1 into permissible cells remains an extremely attractive and underexploited therapeutic intervention point. We have previously demonstrated the ability to extend the chemotypes available for optimization in the entry inhibitor class using computational means. Here, we continue this effort, designing and testing three novel compounds with the ability to inhibit HIV-1 entry. We demonstrate that alteration of the core moiety of these entry inhibitors directly influences the potency of the compounds, despite common proximal and distal groups...
August 3, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/30080959/enzyme-mediated-site-specific-protein-coupling-strategies-for-surface-based-binding-assays
#8
Wolfgang Ott, Ellis Durner, Hermann E Gaub
Covalent surface immobilization of proteins for binding assays is typically performed non-specifically via lysine residues. However, receptors that either have lysines near their binding pockets, or whose presence at the sensor surface is electrostatically disfavoured, can be hard to probe. To overcome these limitations and to improve the homogeneity of surface functionalization, we adapted and optimized three different enzymatic coupling strategies (4´-phosphopantetheinyl transferase, Sortase A and asparaginyl endopeptidase) for biolayer interferometry surface modification...
August 6, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/30079217/selective-oxymetalation-of-terminal-alkynes-via-6-endo-cyclization-mechanistic-investigation-and-application-to-the-efficient-synthesis-of-4-substituted-isocoumarins
#9
Yuji Kita, Tetsuji Yata, Yoshihiro Nishimoto, Kouji Chiba, Makoto Yasuda
The cyclization of heteroatom-containing alkynes with π acidic metal salts is an attractive method to prepare heterocycles because the starting materials are readily available and the organometallic compounds are useful synthetic intermediates. A new organometallic species in the heterocyclization provides an opportunity to synthesize heterocycles that are difficult to obtain. Herein, we describe a novel cyclic oxymetalation of 2-alkynylbenzoate with indium or gallium salts that proceeds with an unusual regioselectivity to give isocoumarins bearing a carbon-metal bond at the 4-position...
July 28, 2018: Chemical Science
https://www.readbyqxmd.com/read/30077905/interaction-of-calmodulin-with-poly-acrylic-acid-brushes-effects-of-high-pressure-ph-value-and-ligand-binding
#10
Artem Levin, Claus Czeslik
Poly(acrylic acid) (PAA) brushes are well-known to interact with proteins in an ionic strength-dependent way. Moreover, they provide a native-like environment that largely maintains the secondary structure and biological activity of adsorbed proteins. Recently, it has been shown that the application of high pressure can lead to a reduced protein adsorption at a PAA brush in the case of a positively charged protein. Here, we analyze the effect of pressure on the interactions between a protein and a PAA brush in more detail...
July 31, 2018: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/30051915/harnessing-the-wisdom-in-colloidal-chemistry-to-make-stable-single-atom-catalysts
#11
REVIEW
Max J Hülsey, Jiaguang Zhang, Ning Yan
Research on single-atom catalysts (SACs), or atomically dispersed catalysts, has been quickly gaining momentum over the past few years. Although the unique electronic structure of singly dispersed atoms enables uncommon-sometimes exceptional-activities and selectivities for various catalytic applications, developing reliable and general procedures for preparing stable, active SACs in particular for applications under reductive conditions remains a major issue. Herein, the challenges associated with the synthesis of SACs are highlighted semiquantitatively and three stabilization techniques inspired by colloidal science including steric, ligand, and electrostatic stabilization are proposed...
July 27, 2018: Advanced Materials
https://www.readbyqxmd.com/read/30044911/noncovalent-electrostatic-interactions-induce-positively-cooperative-binding-of-small-molecules-to-alzheimer-s-and-parkinson-s-disease-related-amyloids
#12
Jessica L Cifelli, Christina C Capule, Jerry Yang
Amyloids are self-assembled protein aggregates that represent a major hallmark of many neurologic and systemic diseases. Among the common features of amyloids is the presence of a high density of multiple binding sites for small molecule ligands, making them an attractive target for design of multimeric binding agents. Here, we demonstrate that noncovalent, intermolecular interactions between a 1:1 mixture of oppositely charged benzothiazole molecules enhances their binding to two different amyloid aggregates: Alzheimer's-related amyloid-β (Aβ) peptides or Parkinson's-related α-synuclein (αS) proteins...
August 2, 2018: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/30044097/functional-and-biomimetic-dna-nanostructures-on-lipid-membranes
#13
Na Wu, Feng Chen, Yue Zhao, Xu Yu, Jing Wei, Yongxi Zhao
Sophisticated and dynamic membrane-anchored DNA nanostructures were developed to mimic variety of membrane proteins, which play crucial roles on cellular functions. DNA biomimetic constructions bound on membranes are capable of modulating the morphologies, physical properties and functions of lipid membranes, via mobility on membranes and/or inherent architectural features. This inspired young field of DNA-lipid-based nanobiomimetic systems is on the foundation of DNA nanotechnology. In this review, we highlight key successes in the development of structural DNA nanotechnology and demonstrated some typical static and dynamic complex DNA nanostructures firstly...
July 25, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/30039184/polynuclear-ruthenium-organometallic-complexes-containing-a-1-3-5-triazine-ligand-synthesis-dna-interaction-and-biological-activity
#14
Floyd A Beckford, Madison B Niece, Brittany P Lassiter, Stephen J Beebe, Alvin A Holder
It is now well established that ruthenium complexes are attractive alternatives to platinum-based anticancer agents. Most of the ruthenium compounds currently under investigation contain a single metal center. The synthesis of multinuclear analogues may provide access to novel complexes with enhanced biological activity. In this work, we have synthesized a set of three trinuclear complexes containing organometallic ruthenium fragments-(arene)RuCl-coordinated to a 2,4,6-tris(di-2-pyridylamino)-1,3,5-triazine core [(Arene = benzene (2), p-cymene (1), or hexamethylbenzene (3)]...
July 23, 2018: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/30033856/molecular-dynamics-and-free-energy-studies-on-the-drosophila-melanogaster-and-leptinotarsa-decemlineata-ecdysone-receptor-complexed-with-agonists-mechanism-for-binding-and-selectivity
#15
Fangfang Wang, Bo Zhou
The ecdysone receptor is a nuclear hormone receptor that plays a pivotal role in insect metamorphosis and development. To address the molecular mechanisms of binding and selectivity, the interactions of two typical agonists Ponasterone A and 20-Hydroxyecdysone with Drosophila melanogaster (DME) and Leptinotarsa decemlineata ecdysone (LDE) receptors were investigated by homology modeling, molecular docking, molecular dynamics simulation and thermodynamic analysis. We discover that: 1) the L5-loop, L11-loop and H12 helix for DME, L7-loop and L11-loop for LDE are more flexible, which affect the global dynamics of the ligand binding pocket, thus facilitating the ligand recognition of ecdysone receptor; 2) several key residues (Thr55/Thr37, Phe109/Phe91, Arg95/Arg77, Arg99/Arg81, Phe108/Leu90 and Ala110/Val92) are responsible for the binding of the proteins; 3) the binding free energy is mainly contributed by the van der Waals forces compared with the electrostatic interactions of ligand and receptor; 4) the computed binding free energy difference between DME-C1 and LDE-C1 is -1...
July 22, 2018: Journal of Biomolecular Structure & Dynamics
https://www.readbyqxmd.com/read/30033171/thermodynamics-of-the-adsorption-of-monoclonal-antibodies-in-phenylboronate-chromatography-affinity-versus-multimodal-interactions
#16
Sara A S L Rosa, C L da Silva, M Raquel Aires-Barros, A C Dias-Cabral, Ana M Azevedo
The aim of this work was to investigate the complex phenomena underlying the adsorption of an anti-human IL-8 (anti-IL8) monoclonal antibody (mAb) to m-aminophenylboronate (m-APBA) by Flow Microcalorimetry (FMC) and to understand the role of non-specific interactions in the adsorption process. FMC was exploited as a dynamic on-line method to measure instantaneous heat energy transfers in order to understand the surface phenomena underlying mAb's adsorption towards the synthetic ligand m-APBA under different pH (7...
July 17, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/30029403/using-zif-8-as-stationary-phase-for-capillary-electrophoresis-separation-of-proteins
#17
Zhongmin Geng, Qianqian Song, Bing Yu, Hailin Cong
Recently, the separation of proteins has received much attention, although many techniques require expensive instrumentation and trained analysts. In this work, a low-cost, effective, and environmental friendship capillary electrophoresis (CE) for proteins separation was first time introduced. The ZIF-8 with outstanding properties of large surface area, and accessible tunnels and cages were coated the inner surface of silica capillary as a separation media by electrostatic interaction. The fast baseline separation of Lys, CC, BSA and RNase A can be obtained within 10 min using the ZIF-8 nanocrystals coated capillary column under the optimum separation conditions...
October 1, 2018: Talanta
https://www.readbyqxmd.com/read/30027444/the-electrostatic-embedding-contribution-to-dft-calculations-of-ligand-amino-acid-residues-interaction
#18
Tamires C da Silva Ribeiro, Marcelo L Lyra, Vinícius Manzoni
In this work, we demonstrate that the inclusion of long-range interactions has a significant impact on the estimation of ligand-protein binding energies. Within the scope of the electrostatically embedded adaptation of the molecular fragmentation with conjugated caps (EE-AMFCC) scheme, we unveil the role played by long-range contributions in distinct levels of quantum mechanical calculations. As a prototypical system, we consider ibuprofen coupled to the human serum albumin. In particular, we show that some relevant ligand-residue interaction energies can only be accurately captured in density functional theory (DFT) approaches when the electrostatic background is properly represented by an explicit point charge distribution...
July 19, 2018: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/30024588/a-two-stage-assembly-with-pei-induced-emission-enhancement-of-au-agncs-amp-and-the-intrinsic-mechanism
#19
Xu Yu, Jiao Liu, Hong-Wei Li, Yuqing Wu
Recently, aggregation-induced emission (AIE) properties have been revealed for some metal nanoclusters (NCs), providing a new approach to improve the quantum yields (QY). In the present study, a two-stage assembly was carried out between adenosine monophosphate capped bimetallic nanoclusters of gold and silver (Au-AgNCs@AMP) and polyethylenimine (PEI), in which the QY was improved from 8.64% to 25.02%, showing obvious assembly induced emission enhancement (AIEE) properties. The intrinsic mechanisms of the assembly and emission enhancement in two stages were studied in depth, which indicated that the electrostatic interaction between the phosphate group in AMP and the amino group in PEI restricted the intramolecular vibration and rotation of capping ligands, and reduced the non-radiative relaxation of the corresponding excited states in stage I; in stage II, the micellization of PEI at high concentration pushed the NCs into a less polar environment and greatly enhanced the metal-metal interaction between them, which facilitated the excited state relaxation dynamics via a radiative pathway...
August 2, 2018: Nanoscale
https://www.readbyqxmd.com/read/30022039/electrostatic-tuning-of-the-ligand-binding-mechanism-by-glu27-in-nitrophorin-7
#20
Stefania Abbruzzetti, Alessandro Allegri, Axel Bidon-Chanal, Hideaki Ogata, Giancarlo Soavi, Giulio Cerullo, Stefano Bruno, Chiara Montali, F Javier Luque, Cristiano Viappiani
Nitrophorins (NP) 1-7 are NO-carrying heme proteins found in the saliva of the blood-sucking insect Rhodnius prolixus. The isoform NP7 displays peculiar properties, such as an abnormally high isoelectric point, the ability to bind negatively charged membranes, and a strong pH sensitivity of NO affinity. A unique trait of NP7 is the presence of Glu in position 27, which is occupied by Val in other NPs. Glu27 appears to be important for tuning the heme properties, but its influence on the pH-dependent NO release mechanism, which is assisted by a conformational change in the AB loop, remains unexplored...
July 18, 2018: Scientific Reports
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