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https://www.readbyqxmd.com/read/28535054/tuning-the-binding-dynamics-of-a-guest-octaacid-capsule-through-non-covalent-anchoring
#1
Suma S Thomas, Hao Tang, Adam Gaudes, Signe B Baggesen, Corinne L D Gibb, Bruce C Gibb, Cornelia Bohne
Hydrophobic or hydrophilic substituents have different effects on the binding dynamics of pyrene derivatives with a 2:1 capsule formed from two octaacid cavitands, showing a subtle interplay of different kinetic factors. Anchoring of the methyl group of 1-methylpyrene within one cavitand slowed the association and dissociation dynamics of the 1:1 complex by at least 1,000 times when compared to the 1:1 complex for pyrene. This slow down for the transient formation of the 1:1 complex is responsible for the overall increase in stability of the 2:1 complex without affecting the overall capsule dissociation...
May 23, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28533982/lid-opening-and-conformational-stability-of-t1-lipase-is-mediated-by-increasing-chain-length-polar-solvents
#2
Jonathan Maiangwa, Mohd Shukuri Mohamad Ali, Abu Bakar Salleh, Raja Noor Zaliha Raja Abd Rahman, Yahaya M Normi, Fairolniza Mohd Shariff, Thean Chor Leow
The dynamics and conformational landscape of proteins in organic solvents are events of potential interest in nonaqueous process catalysis. Conformational changes, folding transitions, and stability often correspond to structural rearrangements that alter contacts between solvent molecules and amino acid residues. However, in nonaqueous enzymology, organic solvents limit stability and further application of proteins. In the present study, molecular dynamics (MD) of a thermostable Geobacillus zalihae T1 lipase was performed in different chain length polar organic solvents (methanol, ethanol, propanol, butanol, and pentanol) and water mixture systems to a concentration of 50%...
2017: PeerJ
https://www.readbyqxmd.com/read/28530720/collective-dehydration-of-ions-in-nano-pores
#3
M P Heuberger, Z Zachariah, N D Spencer, R M Espinosa-Marzal
Hydrated ions can enter nanometre pores that are smaller than the hydrated ion diameter - the associated dehydration mechanism is still poorly understood. Using an adjustable model slit pore between negatively charged mica surfaces, we have followed the dehydration of highly confined Na(+) counter-ions as a function of salt concentration. We applied external load to the slit pore and resolved the induced sub-nanometre film-thickness transitions, in order to gain information about any structural elements present...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28530292/soil-sorption-of-two-nitramines-derived-from-amine-based-co2-capture
#4
Cathrine Brecke Gundersen, Gijs D Breedveld, Lena Foseid, Rolf D Vogt
Nitramines are potentially carcinogens that form from the amines used in post-combustion CO2 capture (PCCC). The soil sorption characteristics of monoethanol (MEA)- and dimethyl (DMA)-nitramines have been assessed using a batch experimental setup, and defined indirectly by measuring loss of nitramine (LC-MS/MS) from the aqueous phase (0.01 M CaCl2 and 0.1% NaN3) after equilibrium had been established with the soil (24 h). Nitramine soil sorption was found to be strongly dependent on the content of organic matter in the soil (r(2) = 0...
May 22, 2017: Environmental Science. Processes & Impacts
https://www.readbyqxmd.com/read/28530285/one-step-formulation-of-nonionic-surfactant-bicelles-nsbs-by-a-double-tailed-polyglycerol-type-nonionic-surfactant
#5
Kenji Aramaki, Chikahiro Iwata, Jitendra Mata, Tetsuya Maehara, Daisuke Aburano, Yuichi Sakanishi, Kyuhei Kitao
Bicelles are generally formed by phospholipid-based systems and are useful for various applications, such as nanocarriers or membrane protein crystallization. The same disc-like assemblies, nonionic surfactant bicelles (NSBs), can also be formed using nonionic amphiphiles, but this has not been reported extensively. We report a novel NSB system that employs the double-tailed nonionic amphiphile, polyglyceryl dialkyl ether (C12CmGn), which has two alkyl chains and a polyglyceryl group. A symmetric-tail molecule, C12C12G13...
May 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28530193/surface-adsorption-of-poisonous-pb-ii-ions-from-water-using-chitosan-functionalised-magnetic-nanoparticles
#6
Femina Carolin Christopher, Saravanan Anbalagan, Ponnusamy Senthil Kumar, Sundar Rajan Pannerselvam, Vinoth Kumar Vaidyanathan
In this study, chitosan functionalised magnetic nano-particles (CMNP) was synthesised and utilised as an effective adsorbent for the removal of Pb(II) ions from aqueous solution. The experimental studies reveal that adsorbent material has finer adsorption capacity for the removal of heavy metal ions. Parameters affecting the adsorption of Pb(II) ions on CMNP, such as initial Pb(II) ion concentration, contact time, solution pH, adsorbent dosage and temperature were studied. The adsorption equilibrium study showed that present adsorption system followed a Freundlich isotherm model...
June 2017: IET Nanobiotechnology
https://www.readbyqxmd.com/read/28528413/dissolved-platinum-concentrations-in-coastal-seawater-boso-to-sanriku-areas-japan
#7
Asami Suzuki Mashio, Hajime Obata, Toshitaka Gamo
Platinum, one of the rarest elements in the earth's crust, is now widely used in a range of products, such as catalytic converters in automobiles and anticancer drugs. Increasing use and dispersal of platinum has the potential to affect aquatic environments. Platinum concentrations in open ocean seawater have been found to be very low (approximately 0.2 pmol/L); however, Pt distributions and biogeochemical cycles in coastal areas are unknown. In this study, we investigated Pt concentrations in coastal waters between the Boso and Sanriku areas, Japan, after the 2011 tsunami...
May 20, 2017: Archives of Environmental Contamination and Toxicology
https://www.readbyqxmd.com/read/28528093/kinetic-and-thermodynamic-compensation-a-current-and-practical-review-for-foods
#8
REVIEW
Alfonso Garvín, Raquel Ibarz, Albert Ibarz
Kinetic and thermodynamic compensations have been reported in many chemical, physical, biological and food processes. Kinetic compensation can be found for any process and when it takes place, it gives information about the reaction mechanism and whether the reaction is controlled by enthalpy or entropy. It consists of the linear relationship between the logarithm of the frequency factor (lnk0) and the activation energy (Ea), both previously obtained from the Arrhenius equation for different values of an environmental variable (e...
June 2017: Food Research International
https://www.readbyqxmd.com/read/28527458/conformation-change-of-an-isotactic-poly-n-isopropylacrylamide-membrane-molecular-dynamics
#9
Irene Adroher-Benítez, Arturo Moncho-Jordá, Gerardo Odriozola
In this work, isotactic Poly (N-Isopropylacrylamide)-PNIPAM-in neat water and in electrolyte solutions is studied by means of molecular dynamics simulations. This is done for an infinitely diluted oligomer and for an assembly of several PNIPAM chains arranged into a planar membrane configuration with a core-shell morphology. We employed two different force fields, AMBER (assisted model building with energy refinement) and OPLS-AA (all atom - optimized potentials for liquid simulations) in combination with extended simple point charge water...
May 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28527431/osmotic-and-diffusio-osmotic-flow-generation-at-high-solute-concentration-ii-molecular-dynamics-simulations
#10
Hiroaki Yoshida, Sophie Marbach, Lydéric Bocquet
In this paper, we explore osmotic transport by means of molecular dynamics (MD) simulations. We first consider osmosis through a membrane and investigate the reflection coefficient of an imperfectly semi-permeable membrane, in the dilute and high concentration regimes. We then explore the diffusio-osmotic flow of a solute-solvent fluid adjacent to a solid surface, driven by a chemical potential gradient parallel to the surface. We propose a novel non-equilibrium MD (NEMD) methodology to simulate diffusio-osmosis, by imposing an external force on every particle, which properly mimics the chemical potential gradient on the solute in spite of the periodic boundary conditions...
May 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28524800/swelling-mechanism-of-urea-crosslinked-starch-lignin-films-in-water
#11
Ariyanti Sarwono, Zakaria Man, M Azmi Bustam, Duvvuri Subbarao, Alamin Idris, Nawshad Muhammad, Amir Sada Khan, Zahoor Ullah
Coating fertilizer particles with thin films is a possibility to control the fertilizer release rates. It is observed that novel urea crosslinked starch-lignin composite thin films, prepared by solution casting, swell on coming into contact with water due to increase in volume by water uptake diffusion. The effect of lignin content, varied from 0% to 20% in steps of 5% and three different temperatures (25°C, 35°C and 45°C) on swelling of the film was investigated. By gravimetric analysis, the equilibrium water uptake and diffusion coefficient decrease with lignin content indicating that the addition of lignin increases the hydrophobicity of the films...
May 19, 2017: Environmental Technology
https://www.readbyqxmd.com/read/28522201/adsorption-of-p-nitrophenols-pnp-on-microalgal-biochar-analysis-of-high-adsorption-capacity-and-mechanism
#12
Heshan Zheng, Wanqian Guo, Shuo Li, Yidi Chen, Qinglian Wu, Xiaochi Feng, Renli Yin, Shih-Hsin Ho, Nanqi Ren, Jo-Shu Chang
Biochars derived from three microalgal strains (namely, Chlorella sp. Cha-01, Chlamydomonas sp. Tai-03 and Coelastrum sp. Pte-15) were evaluated for their capacity to adsorb p-nitrophenols (PNP) using raw microalgal biomass and powdered activated carbon (PAC) as the control. The results show that BC-Cha-01 (biochar from Chlorella sp. Cha-01) exhibited a high PNP adsorption capacity of 204.8mgg(-1), which is 250% and 140% higher than that of its raw biomass and PAC, respectively. The adsorption kinetics and equilibrium are well described with pseudo-second-order equation and Freundlich model, respectively...
May 8, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28521239/seabed-gallery-intakes-investigation-of-the-water-pretreatment-effectiveness-of-the-active-layer-using-a-long-term-column-experiment
#13
Abdullah H A Dehwah, Thomas M Missimer
Seabed gallery intake systems used for seawater reverse osmosis facilities employ the same principle of water treatment as slow sand filtration in freshwater systems. An investigation concerning the effectiveness of the active layer (top layer) in improving raw water quality was conducted by using a long-term bench-scale columns experiment. Two different media types, silica and carbonate sand, were tested in 1 m columns to evaluate the effectiveness of media type in terms of algae, bacteria, Natural Organic Matter (NOM) and Transparent Exopolymer Particles (TEP) removal over a period of 620 days...
May 10, 2017: Water Research
https://www.readbyqxmd.com/read/28521089/nanoporous-block-polymer-thin-films-functionalized-with-bio-inspired-ligands-for-the-efficient-capture-of-heavy-metal-ions-from-water
#14
Jacob Logan Weidman, Ryan A Mulvenna, Bryan W Boudouris, William A Phillip
Heavy metal contamination of water supplies poses a serious threat to public health, prompting the development of novel and sustainable treatment technologies. One promising approach is to molecularly engineer the chemical affinity of a material for the targeted removal of specific molecules from solution. In this work, nanoporous polymer thin films generated from tailor-made block polymers were functionalized with the bio-inspired moieties glutathione and cysteamine for the removal of heavy metal ions, including lead and cadmium, from aqueous solutions...
May 18, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28516245/municipal-solid-waste-derived-biochar-for-the-removal-of-benzene-from-landfill-leachate
#15
Yohan Jayawardhana, S S Mayakaduwa, Prasanna Kumarathilaka, Sewwandi Gamage, Meththika Vithanage
The potential of biochar, produced from fibrous organic fractions of municipal solid waste (MSW), for remediation of benzene, one of the frequently found toxic volatile organic compounds in landfill leachate, was investigated in this study based on various environmental conditions such as varying pH, benzene concentration, temperature and time. At the same time, landfill leachate quality parameters were assessed at two different dump sites in Sri Lanka: Gohagoda and Kurunegala. MSW biochar (MSW-BC) was produced by slow temperature pyrolysis at 450 °C, and the physiochemical characteristics of the MSW-BC were characterized...
May 17, 2017: Environmental Geochemistry and Health
https://www.readbyqxmd.com/read/28513601/vacuum-ultraviolet-spectroscopy-of-the-lowest-lying-electronic-state-in-subcritical-and-supercritical-water
#16
Timothy W Marin, Ireneusz Janik, David M Bartels, Daniel M Chipman
The nature and extent of hydrogen bonding in water has been scrutinized for decades, including how it manifests in optical properties. Here we report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of subcritical and supercritical water. For subcritical water, the spectrum redshifts considerably with increasing temperature, demonstrating the gradual breakdown of the hydrogen-bond network. Tuning the density at 381 °C gives insight into the extent of hydrogen bonding in supercritical water...
May 17, 2017: Nature Communications
https://www.readbyqxmd.com/read/28513177/hydrogen-bonded-structures-of-confined-water-molecules-and-electric-field-induced-shift-of-their-equilibrium-revealed-by-ir-electroabsorption-spectroscopy
#17
Shogo Toda, Shinsuke Shigeto
Water confined on a nanometer scale plays an essential role in various chemical and biological processes. Confined water molecules are often exposed to electric fields as manifested by those that occur on protein surfaces or in electrical double layers, but the electric field effects on confined water are not fully understood. We used IR electroabsorption (EA) spectroscopy with unprecedented sensitivity to observe electric-field-induced changes in the OH stretching absorption of water (H2O) molecules dissolved in 1,4-dioxane, which constitute a simple model system for confined water...
May 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28512707/geochemistry-and-sources-of-fluoride-and-nitrate-contamination-of-groundwater-in-lar-area-south-iran
#18
Mohsen Rezaei, Masume Nikbakht, Ata Shakeri
Groundwater quality in bone-dry and semiarid areas of Iran is decreasing because of contaminants from natural origins and anthropogenic sources. Among many harmful contaminants, nitrate and fluoride ions are more common. This study was carried out with the aim of determining geochemical processes controlling chemistry of groundwater with special reference to nitrate and fluoride enrichment in groundwater in Lar plain aquifer, south of Iran. Groundwater samples were collected from 17 sites and analyzed for main constituents (Na, K, Ca, Mg, Cl, SO4(2-), HCO3(-), F(-), and NO3(-))...
May 16, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28510040/fibril-formation-from-the-amyloid-%C3%AE-peptide-is-governed-by-a-dynamic-equilibrium-involving-association-and-dissociation-of-the-monomer
#19
REVIEW
Masaru Hoshino
Here I review the molecular mechanisms by which water-soluble monomeric amyloid-β (Aβ) peptides are transformed into well-organized supramolecular complexes called amyloid fibrils. The mechanism of amyloid formation is considered theoretically on the basis of experimental results, and the structural and mechanistic similarities of amyloid fibrils to three-dimensional crystals are highlighted. A number of important results from the literature are described. These include the observation that a correct ratio of monomer association and dissociation rate constants is key for formation of well-organized amyloid fibrils...
February 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/28508331/is-pesticide-sorption-by-constructed-wetland-sediments-governed-by-water-level-and-water-dynamics
#20
Céline Gaullier, Sylvie Dousset, David Billet, Nicole Baran
Constructed wetlands (CWs) are used to reduce the pesticide inputs from tile drainage or run-off to surface water. Their effectiveness appears variable and remains to be better characterized and understood. The aim of this study was to assess the influences of two hydraulic parameters (i.e., dynamics and water level) on the sorption process occurring in CWs. Then, two solid/liquid ratios were studied (1/1 and 1/5) to mimic the water level variation in the field, and two agitation speeds were used (none and gentle agitation) to simulate different water dynamics (stagnation and flow pass, respectively)...
May 15, 2017: Environmental Science and Pollution Research International
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