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Wenyu Wang, Qinyan Yue, Ruihua Li, Fan Bu, Xue Shen, Baoyu Gao
This study investigated membrane fouling in a coagulation/ultrafiltration (C-UF) process by comparing the floc properties and humic acid (HA) removal efficiency of three hydrous Al(III) species (Ala , Alb , and Alc ). The results indicated that the coagulation and membrane mechanisms were different for all three Al species because of the differences in floc properties. The HA removal efficiency increased with increasing Al dosage until an equilibrium was reached at the optimal dosage of 6 mg L-1 . In addition, membrane fouling gradually decreased as the Al dosages increased...
February 19, 2018: Chemosphere
Romain Walcker, Laure Gandois, Christophe Proisy, Dov Corenblit, Éric Mougin, Christophe Laplanche, Raghab Ray, François Fromard
The role of mangroves in the blue carbon stock is critical and requires special focus. Mangroves are carbon-rich forests that are not in steady-state equilibrium at the decadal time scale. Over the last decades, the structure and zonation of mangroves have been largely disturbed by coastal changes and land use conversions. The amount of time since the last disturbance is a key parameter determining forest structure, but it has so far been overlooked in mangrove carbon stock projections. In particular, the carbon sequestration rates among mangrove successional ages after (re)establishment are poorly quantified and not used in large scale estimations of the blue carbon stock...
February 23, 2018: Global Change Biology
Jeremiah J Minich, Megan M Morris, Matt Brown, Michael Doane, Matthew S Edwards, Todd P Michael, Elizabeth A Dinsdale
Global climate change includes rising temperatures and increased pCO2 concentrations in the ocean, with potential deleterious impacts on marine organisms. In this case study we conducted a four-week climate change incubation experiment, and tested the independent and combined effects of increased temperature and partial pressure of carbon dioxide (pCO2), on the microbiomes of a foundation species, the giant kelp Macrocystis pyrifera, and the surrounding water column. The water and kelp microbiome responded differently to each of the climate stressors...
2018: PloS One
W James Morgan, Devin A Matthews, Magnus Ringholm, Jay Agarwal, Justin Z Gong, Kenneth Ruud, Wesley D Allen, John F Stanton, Henry F Schaefer
Geometric energy derivatives which rely on core-corrected focal-point energies extrapolated to the complete basis set (CBS) limit of coupled cluster theory with iterative and noniterative quadruple excitations, CCSDTQ and CCSDT(Q), are used as elements of molecular gradients and, in the case of CCSDT(Q), expansion coefficients of an anharmonic force field. These gradients are used to determine the CCSDTQ/CBS and CCSDT(Q)/CBS equilibrium structure of the S0 ground state of H2 CO where excellent agreement is observed with previous work and experimentally derived results...
February 23, 2018: Journal of Chemical Theory and Computation
Susanne Liese, Roland R Netz
Multivalency achieves strong, yet reversible binding by the simultaneous formation of multiple weak bonds. It is a key interaction principle in biology and promising for the synthesis of high-affinity inhibitors of pathogens. We present a molecular model for the binding affinity of synthetic multivalent ligands onto multivalent receptors consisting of n receptor units arranged on a regular polygon. Ligands consist of geometrically matching rigid polygonal core to which monovalent ligand units are attached via flexible linker polymers, closely mimicking existing experimental designs...
February 23, 2018: ACS Nano
Elisa E Greciano, Beatriz Matarranz, Luis- Sanchez
The self-assembly of a series of N-annulated perylenes are investigated. Compound 1, endowed with inner amides, shows a pathway complexity in which the inactivated monomeric species, stored as an off-pathway aggregate, kinetically switch into on-pathway, helical structures. This out-of-equilibrium process can be accelerated by the addition of seeds. The outer amides in 2 also affords kinetically trapped monomers that evolve to form superhelical structures. The fast evolution of the monomeric species and the high stability of the final interdigitated supramolecular entities impede performing a seeded supramolecular polymerization...
February 23, 2018: Angewandte Chemie
Joseline A Houwman, Adrie H Westphal, Antonie J W G Visser, Jan Willem Borst, Carlo P M van Mierlo
Flavodoxins have a protein topology that can be traced back to the universal ancestor of the three kingdoms of life. Proteins with this type of architecture tend to temporarily misfold during unassisted folding to their native state and form intermediates. Several of these intermediate species are molten globules (MGs), which are characterized by a substantial amount of secondary structure, yet without the tertiary side-chain packing of natively folded proteins. An off-pathway MG is formed at physiological ionic strength in the case of the F44Y variant of Azotobacter vinelandii apoflavodoxin (i...
February 23, 2018: Physical Chemistry Chemical Physics: PCCP
Jie Tan, Xiaoming Zhang, Wenguan Liu, Xiujie He, Mingwen Zhao
Using non-equilibrium Green's function formalism combined with density functional theory (DFT) calculations, we investigate the significant changes in electronic and transport properties of triangle graphene spirals (TGSs) in response to external strain. Tunable negative differential resistance (NDR) behavior is predicted. The NDR bias region, NDR width, and peak-to-valley ratio can be well tuned by external strain. Further analysis shows that these peculiar properties can be attributed to the dispersion widths of the pz orbitals...
February 23, 2018: Nanotechnology
Vijay M Miriyala, Jan Řezáč
Semiempirical QM methods with corrections for non-covalent interactions provide a favorable combination of accuracy and computational efficiency what makes them useful tool for a study of large molecular systems. It was, however, noted that the accuracy of these method deteriorates at intermolecular distances shorter than equilibrium. In this work, we explore this issue systematically using a newly developed data set of benchmark interaction energies named R160x6. This data set maps repulsive contacts in organic molecules, and it consists of 160 model complexes for which six points along the dissociation curve are provided...
February 23, 2018: Journal of Physical Chemistry. A
Alex J Guseman, Shannon Leigh Speer, Gerardo M Perez Goncalves, Gary J Pielak
Protein-protein interactions are fundamental to biology, yet are rarely studied under physiologically-relevant conditions where the concentration of macromolecules can exceed 300 g/L. These high concentrations cause cosolute-complex contacts that are absent in dilute buffer. Understand-ing such interactions is important because they organize the cellular interior. We used 19F NMR, the dimer-forming A34F variant of the model protein GB1 and the cosolutes bovine serum albumin (BSA) and lysozyme to assess the effects of repulsive and attractive charge-charge dimer-cosolute interac-tions on dimer stability...
February 23, 2018: Biochemistry
A Odorico, E Rünneburger, A Le Rouzic
Understanding the importance of non-genetic heredity in the evolutionary process is a major topic in modern evolutionary biology. We modified a classical gene network model by allowing parental transmission of gene expression, and studied its evolutionary properties through individual-based simulations. We identified ontogenetic time (i.e. the time gene networks have to stabilize before being submitted to natural selection) as a crucial factor in determining the evolutionary impact of this phenotypic inheritance...
February 23, 2018: Journal of Evolutionary Biology
Kun Cai, Jiao Shi, Jingzhou Yu, Qing H Qin
When argon is used as a protecting gas in the fabrication or working environment of a nanodevice, absorption of some argon atoms onto the surface of the device lead to different responses. In this work, the rotation of the rotor in a carbon nanotube (CNT)-based rotary nanomotor in argon environment is investigated. In the rotary nanomotor, two outer CNTs act as the stator and are used to constrain the inner CNT (i.e., the rotor). The rotor is driven to rotate by the stator due to their collision during thermal vibration of their atoms...
February 22, 2018: Scientific Reports
Georg K A Hochberg, Dale A Shepherd, Erik G Marklund, Indu Santhanagoplan, Matteo T Degiacomi, Arthur Laganowsky, Timothy M Allison, Eman Basha, Michael T Marty, Martin R Galpin, Weston B Struwe, Andrew J Baldwin, Elizabeth Vierling, Justin L P Benesch
Oligomeric proteins assemble with exceptional selectivity, even in the presence of closely related proteins, to perform their cellular roles. We show that most proteins related by gene duplication of an oligomeric ancestor have evolved to avoid hetero-oligomerization and that this correlates with their acquisition of distinct functions. We report how coassembly is avoided by two oligomeric small heat-shock protein paralogs. A hierarchy of assembly, involving intermediates that are populated only fleetingly at equilibrium, ensures selective oligomerization...
February 23, 2018: Science
Arya Das, Sk Musharaf Ali
Tri-isoamyl phosphate (TiAP) has been proposed to be an alternative for tri-butyl phosphate (TBP) in the Plutonium Uranium Extraction (PUREX) process. Recently, we have successfully calibrated and tested all-atom optimized potentials for liquid simulations using Mulliken partial charges for pure TiAP, TBP, and dodecane by performing molecular dynamics (MD) simulation. It is of immense importance to extend this potential for the various molecular properties of TiAP and TiAP/n-dodecane binary mixtures using MD simulation...
February 21, 2018: Journal of Chemical Physics
Jianmin Tao, John P Perdew, Hong Tang, Chandra Shahi
Nanostructures can be bound together at equilibrium by the van der Waals (vdW) effect, a small but ubiquitous many-body attraction that presents challenges to density functional theory. How does the binding energy depend upon the size or number of atoms in one of a pair of identical nanostructures? To answer this question, we treat each nanostructure as a whole object, not as a collection of atoms. Our calculations start from an accurate static dipole polarizability for each considered nanostructure, and an accurate equilibrium center-to-center distance for the pair (the latter from experiment or from the vdW-DF-cx functional)...
February 21, 2018: Journal of Chemical Physics
Tapan K Mankodi, Upendra V Bhandarkar, Bhalchandra P Puranik
A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort...
February 21, 2018: Journal of Chemical Physics
M Makavitskaya, D Svistunenko, I Navaselsky, P Hryvusevich, V Mackievic, C Rabadanova, E Tyutereva, V Samokhina, D Straltsova, A Sokolik, O Voitsekhovskaja, V Demidchik
Ascorbate is not often considered as a signalling molecule in plants. This study demonstrates that, in Arabidopsis roots, exogenous L-ascorbic acid triggers a transient increase of the cytosolic free calcium activity ([Ca2+]cyt.) that is central to plant signalling. Exogenous copper and iron stimulates the ascorbate-induced [Ca2+]cyt. elevation while cation channel blockers, free radical scavengers, low extracellular [Ca2+], transition metal chelators and removal of the cell wall inhibit this reaction. These data show that apoplastic redox-active transition metals are involved in the ascorbate-induced [Ca2+]cyt...
February 17, 2018: Journal of Experimental Botany
S E Speidel, B A Buckley, R J Boldt, R M Enns, J Lee, M L Spangler, M G Thomas
Reproductive performance is the most important component of cattle production from the standpoint of economic sustainability of commercial beef enterprises. Heifer Pregnancy (HPG) and Stayability (STAY) genetic predictions are two selection tools published by the Red Angus Association of America (RAAA) to assist with improvements in reproductive performance. Given the importance of HPG and STAY to the profitability of commercial beef enterprises, the objective of this study was to identify QTL associated with both HPG and STAY in Red Angus cattle...
February 19, 2018: Journal of Animal Science
Joseph A Waldron, Farheen Raza, John Le Quesne
Increased activity of the mRNA helicase eIF4A drives cellular malignancy by reprogramming cellular translation, and eIF4A activity is the direct or indirect target of many emerging cancer therapeutics. The enriched presence of (GGC)4 motifs, which have the potential to fold into two-layered G-quadruplexes, within the 5'UTRs of eIF4A-dependent mRNAs suggests that eIF4A is required for the unwinding of these structures within these eIF4A-controlled mRNAs. However, the existence of folded G-quadruplexes within cells remains controversial, and G-quadruplex folding is in direct competition with classical Watson-Crick based secondary structures...
February 19, 2018: Nucleic Acids Research
Yan-Ling Liu, Xiao-Mao Wang, Hong-Wei Yang, Yuefeng F Xie
Adsorption of trace organic compounds (TrOCs) onto the membrane materials has a great impact on their rejection by nanofiltration (NF) and reverse osmosis (RO) membranes. This study aimed to investigate the difference in adsorption of various pharmaceuticals (PhACs) onto different NF/RO membranes and to demonstrate the necessity of isolating the polyamide (PA) active layer from the polysulfone (PS) support layer for adsorption characterization and quantification. Both the isolated PA layers and the PA+PS layers of NF90 and ESPA1 membranes were used to conduct static adsorption tests...
February 16, 2018: Chemosphere
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