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Charge screening

Adam Wang, Doohwan Jung, Jongseok Park, Gregory Junek, Hua Wang
Electrochemical interfaces with low-impedance, high biocompatibility, and long-term stability are of paramount importance for microelectrode arrays (MEAs) widely used in numerous cellular sensing/stimulation applications, e.g., brain interface, electroceuticals, neuroprosthetics, drug discovery, chemical screening, and fundamental biological research. This is increasingly critical since sensing/actuations at sub-cellular resolution necessitate ultra-miniaturized electrodes, which exhibit exacerbated electrochemical interfaces, especially on interfacial impedance...
March 15, 2019: IEEE Transactions on Nanobioscience
Samantha Micciulla, Yuri Gerelli, Emanuel Schneck
The outer membrane of Gram-negative bacteria is of great scientific interest because it mediates the action of antimicrobial agents. The membrane surface is composed of lipopolysaccharide (LPS) molecules with negatively charged oligosaccharide headgroups. To a certain fraction, LPSs additionally display linear polysaccharides termed O-side chains (OSCs). Structural studies on bacterial outer surfaces models, based on LPS monolayers at air-water interfaces, have so far dealt only with rough mutant LPSs lacking these OSCs...
February 28, 2019: Biophysical Journal
Bartholomäus Danielczak, Annette Meister, Sandro Keller
Most membrane-solubilising amphiphilic copolymers such as diisobutylene/maleic acid (DIBMA) and styrene/maleic acid (SMA) carry high negative charge densities. Their polyanionic character results in strong Coulombic repulsion, both between polymer chains and lipid membranes during the solubilisation process as well as among polymer-encapsulated nanodiscs after solubilisation. Coulombic repulsion is attenuated by charge screening and, more efficiently, by counterion association, which is particularly strong for multivalent cations binding to polyanionic copolymers...
March 12, 2019: Chemistry and Physics of Lipids
Ahmed A Khorshed, Mohamed Khairy, Craig E Banks
Hypertension increases the risk of heart disease and stroke, is commonly known as a silent killer disease and considered as one of the key risk factor for premature death and disability over the world. Herein, we report for the first time a sensitive, costless and reproducible voltammetric method for individual determination of five antihypertensive drugs namely, propranolol (PRO), timolol (TIM), amlodipine (AML), amiloride (AMI) and triamterene (TRI) using differential pulse voltammetry at bare/unmodified screen-printed carbon electrodes (SPEs) in presence of sodium dodecyl sulfate (SDS)...
June 1, 2019: Talanta
Yannick Van Wanseele, Jana Bongaerts, Karen Segers, Johan Viaene, Dimitri De Bundel, Yvan Vander Heyden, Ilse Smolders, Ann Van Eeckhaut
With increasing evidence of the important role of peptides in pathophysiological processes, a trend towards the development of highly sensitive bioanalytical methods is ongoing. Inherent to the electrospray ionization process of peptides and proteins is the production of multiple charge states which may hamper proper and sensitive method development. Supercharging agents allow modifying the maximal charge state and the corresponding distribution of charges, thereby potentially increasing the number of ions reaching the detector in selected reaction monitoring mode...
June 1, 2019: Talanta
Jingtong Hou, Ruth Cong, Michi Izumi-Willcoxon, Hana Ali, Yi Zheng, Ericka Bermudez, Mark McDonald, Mark Nelson, Takashi Yamamoto
A novel Bacillus thuringiensis Cry protein, Cry8Hb, active against Diabrotica virgifera virgifera (Western corn rootworm, WCRW) was discovered. Unexpectedly, the anti-rootworm activity of the Cry8Hb toxin was enhanced significantly by fusing Escherichia coli maltose binding protein (MBP) to this Cry toxin. While the exact mechanism of the activity enhancement remains indefinite, it is probable that the enhancement is a result of increased solubility of the MBP-Cry8Hb fusion in the rootworm midgut. This hypothesis was examined using a synthetic Cry3 protein called IP3-1, which was not soluble at a neutral pH like Cry8Hb and marginally active to WCRW...
March 14, 2019: Toxins
Andreia F Santos, Aline L Arim, Daniela V Lopes, Licínio M Gando-Ferreira, Margarida J Quina
Phosphorus scarcity has become a significant issue in the European Union (EU) during 21st Century, due to its relevance as an irreplaceable macronutrient for life, and because of the total dependency of EU regarding imports. This work aims to evaluate the phosphorus recovery by adsorption in batch and fixed-bed column, using a thermally modified eggshell as an adsorbent. The screening phase revealed that calcined eggshell at 700 °C (CES700) is the most suitable material compared with the other thermally modified eggshells tested...
March 12, 2019: Journal of Environmental Management
Wei Zhao, Sheng Bi, Cheng Zhang, Philip D Rack, Guang Feng
Most studies of ionic liquid (IL) gated field effect transistors (FETs) focus on the extremely large electric field and capacitance induced in liquid/solid interfaces and correspondingly the significantly enhanced carrier density in semiconductors, which can appreciably improve the gating performance. However, how to boost the switching speed, another key property of gating performance of FETs, has been rarely explored. In this work, the gating performance of molybdenum disulfide (MoS2) FETs, gated by the mixtures of IL/organic solvent (1-butyl-3-methylimidazolium tetrafluoroborate/acetonitrile, [Bmim][BF4]/ACN) at different ion concentrations, is investigated for both dynamic and static properties by a combination of molecular dynamics simulation and resistance network analysis...
March 15, 2019: ACS Applied Materials & Interfaces
Chaode Cen, Jun Wu, Yong Zhang, Cong Luo, Lina Xie, Xin Zhang, Xiaolan Yang, Ming Li, Yang Bi, Tingyu Li, Tongchuan He
This study aimed to improve the magnetofection of MG-63 osteoblasts by integrating the use of a novel uniform magnetic field with low molecular weight polyethylenimine modified superparamagnetic iron oxide nanoparticles (PEI-SPIO-NPs). The excellent characteristics of PEI-SPIO-NPs such as size, zeta potential, the pDNA binding and protective ability were determined to be suitable for gene delivery. The novel uniform magnetic field enabled polyethylenimine-modified superparamagnetic iron oxide nanoparticles/pDNA complexes (PEI-SPIO-NPs/pDNA complexes) to rapidly and uniformly distribute on the surface of MG-63 cells, averting local transfection and decreasing disruption of the membrane caused by the centralization of positively charged PEI-SPIO-NPs, thereby increasing the effective coverage of magnetic gene carriers during transfection, and improving magnetofection efficiency...
March 12, 2019: Nanoscale Research Letters
Michael Lückmann, Mette Trauelsen, Marie A Bentsen, Tinne A D Nissen, Joao Martins, Zohreh Fallah, Mads M Nygaard, Elena Papaleo, Kresten Lindorff-Larsen, Thue W Schwartz, Thomas M Frimurer
The long-chain fatty acid receptor FFAR1/GPR40 binds agonists in both an interhelical site between the extracellular segments of transmembrane helix (TM)-III and TM-IV and a lipid-exposed groove between the intracellular segments of these helices. Molecular dynamics simulations of FFAR1 with agonist removed demonstrated a major rearrangement of the polar and charged anchor point residues for the carboxylic acid moiety of the agonist in the interhelical site, which was associated with closure of a neighboring, solvent-exposed pocket between the extracellular poles of TM-I, TM-II, and TM-VII...
March 14, 2019: Proceedings of the National Academy of Sciences of the United States of America
Reem Khan, Sondes Ben Aissa, Tauqir A Sherazi, Gaelle Catanante, Akhtar Hayat, Jean Louis Marty
In the present work, an aptasensing platform was developed for the detection of a carcinogenic mycotoxin termed patulin (PAT) using a label-free approach. The detection was mainly based on a specific interaction of an aptamer immobilized on carbon-based electrode. A long linear spacer of carboxy-amine polyethylene glycol chain (PEG) was chemically grafted on screen-printed carbon electrodes (SPCEs) via diazonium salt in the aptasensor design. The NH₂-modified aptamer was then attached covalently to carboxylic acid groups of previously immobilized bifunctional PEG to build a diblock macromolecule...
March 13, 2019: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Roman Korol, Dvira Segal
First-principles calculations of charge transfer in DNA molecules are computationally expensive given that conducting charge carriers interact with intra- and intermolecular atomic motion. Screening sequences, for example, to identify excellent electrical conductors, is challenging even when adopting coarse-grained models and effective computational schemes that do not explicitly describe atomic dynamics. We present a machine learning (ML) model that allows the inexpensive prediction of the electrical conductance of millions of long double-stranded DNA (dsDNA) sequences, reducing computational costs by orders of magnitude...
March 13, 2019: Journal of Physical Chemistry. B
Shaoqing Dong, Zhiqin Yuan, Yanjun Lin, Caifeng Ding, Chao Lu
The rapid and effective recognition techniques for crystal facets in noble metal nanocrystals (NCs) are highly desirable in evaluation of their catalytic performances. Herein, it was found that the variation trend of cataluminescence (CTL) intensity in the presence of propanol was proportional to the crystal facets index change of LDH-supported Pd@Au NCs. The mechanism investigation for the propanol-triggered CTL on the surface of layered double hydroxides (LDH)-supported Pd@Au NCs revealed that the abundant negative charge in high-index facet of LDH-supported Pd@Au NCs facilitated to the electron transfer between NCs and volatile propanol, resulting in acceleration of the CTL reactions...
March 13, 2019: Analytical Chemistry
Mary E Krause, Erinc Sahin
Development of a robust biologic drug product is accomplished by extensive formulation and process development screening studies; however, even in the most optimal formulation, a protein can undergo spontaneous degradation during manufacture, storage, and clinical use. Chemical changes to amino acid residues, such as oxidation of methionine or tryptophan, or changes in charge such as deamidation or carbonylation, can induce conformational changes in the overall protein structure, potentially leading to changes in physical - in addition to chemical - stability...
March 9, 2019: Current Opinion in Biotechnology
Juanjuan Liu, Stacey Marie Louie, Christopher Pham, Chong Dai, Dongli Liang, Yandi Hu
To better understand the fate and transport of ferrihydrite nanoparticles (FNPs), which carry many contaminants in natural and engineered aquatic environments, the aggregation of FNPs was systematically investigated in this study. The pH isoelectric point (pHIEP ), surface zeta potential, and particle size evolutions of FNPs were measured under varied aqueous conditions using dynamic light scattering (DLS). The influence of pH (5.0 ± 0.1 and 7.0 ± 0.1), ionic strength (IS), electrolytes (NaCl, CaCl2 and Na2 SO4 ), and organics (humic acid, fulvic acid and CH3 COONa) on the aggregation behaviors of FNPs were explored...
March 4, 2019: Environmental Research
Michael Rubinstein, Qi Liao, Sergey Panyukov
We develop a scaling theory and perform molecular dynamic simulations of weakly interacting coacervates with electrostatic interaction energy per charge less than thermal energy kT . Such liquid coacervates formed by oppositely charged polyelectrolytes can be asymmetric in charge density and number of charges per chain. We predict that these coacervates form interpenetrating solutions with two correlation lengths and two qualitatively different types of conformations of polyelectrolytes with lower and higher charge densities, which are analogous to chain conformations in quasi-neutral and in polyelectrolyte solutions, respectively...
December 11, 2018: Macromolecules
Maryan Morel, Emmanuel Bacry, Stéphane Gaïffas, Agathe Guilloux, Fanny Leroy
With the increased availability of large electronic health records databases comes the chance of enhancing health risks screening. Most post-marketing detection of adverse drug reaction (ADR) relies on physicians' spontaneous reports, leading to under-reporting. To take up this challenge, we develop a scalable model to estimate the effect of multiple longitudinal features (drug exposures) on a rare longitudinal outcome. Our procedure is based on a conditional Poisson regression model also known as self-controlled case series (SCCS)...
March 8, 2019: Biostatistics
W I Garcia-Garcia, A Vidal-Limon, A A Arrocha-Arcos, L A Palomares, O T Ramirez, M Miranda-Hernández
This paper reports a theoretical and experimental investigation on the recombinant protein rotavirus VP6 as a bioelectrochemical interface. Our motivation arises from the highly active zones of VP6 which can interact with biological structures and metals, as well as its useful features such as self-assembly, polymorphism, and active surface charge. A molecular simulation study was performed to analyze the charge transfer properties of theVP6 trimer under an applied electric field. The electrostatic properties were evaluated via the nonlinear second-order Poisson-Boltzmann equation, using finite element methods based on parameter discretization and calculation of solute/solvent interaction forces, which account for mean-field screening effects...
February 27, 2019: Bioelectrochemistry
Christian Kunkel, Christoph Schober, Harald Oberhofer, Karsten Reuter
Modern materials discovery and design studies often rely on the computational screening of large databases. Complementing experimental databases, virtual databases are thereby increasingly established through the first-principles calculation of computationally inexpensive, but for a given application, decisive microscopic quantities of the system. These so-called descriptors are calculated for vast numbers of candidate materials. In general, the sheer volume of datapoints generated in such studies precludes an in depth human analysis...
March 7, 2019: Journal of Molecular Modeling
Leili Javidpour, Anže Lošdorfer Božič, Rudolf Podgornik, Ali Naji
Electrostatic interactions play important roles in the formation and stability of viruses and virus-like particles (VLPs) through processes that often involve added, or naturally occurring, multivalent ions. Here, we investigate the electrostatic or osmotic pressure acting on the proteinaceous shell of a generic model of VLPs, comprising a charged outer shell and a metallic nanoparticle core, coated by a charged layer and bathed in an aqueous electrolyte solution. Motivated by the recent studies accentuating the role of multivalent ions for the stability of VLPs, we focus on the effects of multivalent cations and anions in an otherwise monovalent ionic solution...
March 7, 2019: Scientific Reports
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