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https://www.readbyqxmd.com/read/29793214/balanced-design-for-the-feasible-super-rocket-fuels-a-first-principle-study-on-gauche-chn-7-and-chn-3
#1
Tao Yu, Maohua Lin, Bo Wu, Jintian Wang, Chi-Tay Tsai
On the basis of the framework of cubic gauche nitrogen (cg-N), six one-eighth methanetriyl groups (>CH-) substitutes and fifteen one-fourth >CH- substitutes were optimized using the first-principle calculations based on density functional theory (DFT). Both one-eighth and one-fourth substitutes still keep the gauche structures with the simple formula CHN7 and CHN3 , respectively. The most thermodynamic stable gauche CHN7 and CHN3 are P21 qtg-C2 H2 N14 I and P21 qtg-C4 H4 N12 III, respectively. No probability density of C-C single bonds and high probability densities of C-N-C structures were found in the two substitutes...
May 16, 2018: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/29793209/effect-of-thermal-pretreatment-on-chemical-composition-physical-structure-and-biogas-production-kinetics-of-wheat-straw
#2
Asad Ayub Rajput, Zeshan, Chettiyappan Visvanathan
Hard lignocellulosic structure of wheat straw is the main hindrance in its anaerobic digestion. Thus, a laboratory scale batch experiment was conducted to study the effect of thermal pretreatment on anaerobic digestion of wheat straw. For this purpose, different thermal pretreatment temperatures of 120, 140, 160 and 180 °C were studied and the results were compared with raw wheat straw. Significant differences in biogas production were observed at temperature higher than 160 °C. Highest biogas yield of 615 Nml/gVS and volatile solids reduction of 69% was observed from wheat straw pretreated at 180 °C...
May 21, 2018: Journal of Environmental Management
https://www.readbyqxmd.com/read/29793161/exposure-of-microcystis-aeruginosa-to-hydrogen-peroxide-and-titanium-dioxide-under-visible-light-conditions-modeling-the-impact-of-hydrogen-peroxide-and-hydroxyl-radical-on-cell-rupture-and-microcystin-degradation
#3
Che-Wei Chang, Xiangchen Huo, Tsair-Fuh Lin
The aims of this study are to evaluate, under visible light conditions, the ability of H2 O2 and TiO2 to produce OH, their quantitative impacts on the cell integrity of Microcystis, and the subsequent release and degradation of microcystins (MCs). A sequential reaction model was developed, including one sub-model to simulate the rupture kinetics for cell integrity of Microcystis, and another to describe the release and degradation of MCs. For cell rupture, the dual-oxidant Delayed Chick-Watson model (DCWM) and dual-oxidant Hom model (HM) were first proposed and developed, giving excellent simulation results of cell rupture kinetics...
May 14, 2018: Water Research
https://www.readbyqxmd.com/read/29793143/oxidation-at-c-16-enhances-butyrylcholinesterase-inhibition-in-lupane-triterpenoids
#4
María Julia Castro, Victoria Richmond, María Belén Faraoni, Ana Paula Murray
A set of triterpenoids with different grades of oxidation in the lupane skeleton were prepared and evaluated as cholinesterase inhibitors. Allylic oxidation with selenium oxide and Jones's oxidation were employed to obtain mono-, di- and tri-oxolupanes, starting from calenduladiol (1) and lupeol (3). All the derivatives showed a selective inhibition of butyrylcholinesterase over acetylcholinesterase (BChE vs. AChE). A kinetic study proved that compounds 2 and 9, the more potent inhibitors of the series, act as competitive inhibitors...
May 17, 2018: Bioorganic Chemistry
https://www.readbyqxmd.com/read/29793109/17%C3%AE-estradiol-as-precursors-of-cl-br-dbps-in-the-disinfection-process-of-different-water-samples
#5
Yanan Shao, Zihan Pan, Chuan Rong, Yinghui Wang, Hongxiang Zhu, Yuanyuan Zhang, Kefu Yu
During chlorine disinfection process, reactions between the disinfectant and 17β-estradiol (E2) lead to the formation of halogenated disinfection byproducts (DBPs) which can be a risk to both ecosystem and human health. The degradation and transformation products of E2 in sodium hypochlorite (NaClO) disinfection processes of different water samples were investigated. The reaction kinetics research showed that the degradation rates of E2 were considerably dependent on the initial pH value and the types of water samples...
May 21, 2018: Environmental Pollution
https://www.readbyqxmd.com/read/29793083/optimization-adsorption-of-norfloxacin-onto-polydopamine-microspheres-from-aqueous-solution-kinetic-equilibrium-and-adsorption-mechanism-studies
#6
Yibei Wan, Xiao Liu, Penglei Liu, Lei Zhao, Weihua Zou
Polydopamine microspheres (PDMPs) synthesized by a facile solution oxidation method were adopted as a potential adsorbent for the removal of Norfloxacin (NOR) from aqueous solution. The morphologies and properties of PDMPs were characterized using TEM, SEM, FTIR and pHPZC . Parameters effects such as contact time, initial pH, initial concentration and ionic strength on the adsorption capacity of NOR onto PDMPs were studied. To maximize NOR removal from liquid phase, Box-Behnken experimental design (BBD) combined with response surface modeling (RSM) was employed based on the 17 preliminary experiments at 308 K...
May 21, 2018: Science of the Total Environment
https://www.readbyqxmd.com/read/29793066/rapid-and-effective-removal-of-as-iii-and-as-v-using-spore-ti-4-microspheres
#7
Lijuan Lan, Bingjie Zheng, Yao Zhang, Yonggang Hu
Removing arsenic from aquatic environments has become an urgent problem worldwide. In this study, Ti4+ - loaded bacterial spore were adopted as a novel adsorbent (spore@Ti4+ microspheres) for the adsorption efficient removal of arsenite (As(III)) and arsenate (As(V)). The developed adsorbents were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS). Results indicated that the adsorption kinetics was well described by a pseudo-second-order kinetic model, and the adsorption process rapidly achieved equilibrium within 15 min at pH 7...
May 15, 2018: Chemosphere
https://www.readbyqxmd.com/read/29793040/quinones-and-nitroaromatic-compounds-as-subversive-substrates-of-staphylococcus-aureus-flavohemoglobin
#8
Myriam Moussaoui, Lina Misevičienė, Žilvinas Anusevičius, Audronė Marozienė, Florence Lederer, Laura Baciou, Narimantas Čėnas
In microorganisms, flavohemoglobins (FHbs) containing FAD and heme (Fe3+ , metHb) convert NO. into nitrate at the expense of NADH and O2 . FHbs contribute to bacterial resistance to nitrosative stress. Therefore, inhibition of FHbs functions may decrease the pathogen virulence. We report here a kinetic study of the reduction of quinones and nitroaromatic compounds by S. aureus FHb. We show that this enzyme rapidly reduces quinones and nitroaromatic compounds in a mixed single- and two-electron pathway. The reactivity of nitroaromatics increased upon an increase in their single-electron reduction potential (E1 7 ), whereas the reactivity of quinones poorly depended on their E1 7 with a strong preference for a 2-hydroxy-1,4-naphthoquinone structure...
May 21, 2018: Free Radical Biology & Medicine
https://www.readbyqxmd.com/read/29793029/oxidative-degradation-of-atenolol-by-heat-activated-persulfate-kinetics-degradation-pathways-and-distribution-of-transformation-intermediates
#9
Dong Miao, Jianbiao Peng, Xiaohuan Zhou, Li Qian, Mengjie Wang, Li Zhai, Shixiang Gao
Atenolol (ATL) has been widely detected in wastewater and aquatic environment. Although satisfactory removal of ATL from wastewater could be achieved, the mineralization ratio is usually low, which may result in the accumulation of its transformation products in the effluent and cause additional ecological risk to the environment. The aim of this study is to explore the effectiveness of heat activated persulfate (PS) in the removal of ATL from wastewater. Influencing factors including temperature, PS dosage, solution pH, existence of NO3 - , Cl- , HCO3 - and Suwannee river fulvic acid (SRFA) were examined...
May 17, 2018: Chemosphere
https://www.readbyqxmd.com/read/29793023/kinetics-and-stereochemistry-of-linb-catalyzed-%C3%AE-hbcd-transformation-comparison-of-in-vitro-and-in-silico-results
#10
Norbert V Heeb, Manuel Mazenauer, Simon Wyss, Birgit Geueke, Hans-Peter E Kohler, Peter Lienemann
LinB is a haloalkane dehalogenase found in Sphingobium indicum B90A, an aerobic bacterium isolated from contaminated soils of hexachlorocyclohexane (HCH) dumpsites. We showed that this enzyme also converts hexabromocyclododecanes (HBCDs). Here we give new insights in the kinetics and stereochemistry of the enzymatic transformation of δ-HBCD, which resulted in the formation of two pentabromocyclododecanols (PBCDols) as first- (P1δ , P2δ ) and two tetrabromocyclododecadiols (TBCDdiols) as second-generation products (T1δ , T2δ )...
May 12, 2018: Chemosphere
https://www.readbyqxmd.com/read/29792957/high-activity-production-of-xylanase-by-pichia-stipitis-purification-characterization-kinetic-evaluation-and-xylooligosaccharides-production
#11
Changhe Ding, Mengxing Li, Yuqi Hu
As an industrially important biological macromolecule, xylanase hydrolyzes xylan to produce xylooligosaccarides (XOS). XOS, with a degree of polymerization (DP) 2 to 4, are important prebiotics used as food ingredients. In this study, xylanase (5536 U/g substrate) was produced by Pichia stipitis using corncob and wheat bran mixture under solid state fermentation. Crude xylanase were purified and biochemically characterized. XOS hydrolyzed by crude and purified xylanases were quantified. Molecular weight of the purified enzyme was around 31...
May 21, 2018: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/29792912/heat-shock-protein-b1-is-required-for-the-prolactin-induced-cytoprotective-effects-on-pancreatic-islets
#12
Rosangela Am Wailemann, Letícia F Terra, Talita C de Oliveira, Ancély F Dos Santos, Vinícius M Gomes, Leticia Labriola
The success of islet transplantation has improved lately. Unfortunately, it is still compromised by cell loss. We have shown that prolactin (PRL) inhibits beta-cell apoptosis and up-regulates the antiapoptotic Heat Shock Protein B1 (HSPB1) in human islets. Since its function in pancreatic islets has not been studied, we explored the role of HSPB1 in PRL-induced beta-cell survival. The significant PRL-induced cytoprotection in control cells was abrogated in HSPB1 silenced cells, overexpression of HSPB1 recovered survival...
May 21, 2018: Molecular and Cellular Endocrinology
https://www.readbyqxmd.com/read/29792911/prolonged-drug-release-properties-for-orodispersible-films-by-combining-hot-melt-extrusion-and-solvent-casting-methods
#13
Isabell Speer, Maren Preis, Jörg Breitkreutz
Orodispersible films (ODFs) are an advantageous dosage form to accomplish patient convenience and compliance in oral drug delivery. They provide a number of special application features, such as the ease of administration without water and suitability for patients with swallowing problems. However, this promising dosage form has been limited to immediate release formulations so far. The aim of this study was to develop a thin film produced by solvent casting, which is rapidly disintegrating when placed in the mouth, but which provides prolonged drug release characteristics by incorporating drug-loaded matrix particles (MPs)...
May 21, 2018: European Journal of Pharmaceutics and Biopharmaceutics
https://www.readbyqxmd.com/read/29792900/the-sulfoconjugation-of-androstenone-and-dehydroepiandrosterone-by-human-and-porcine-sulfotransferase-enzymes
#14
Heidi Laderoute, Christine Bone, E James Squires
Porcine sulfotransferase 2A1 (pSULT2A1) is a key enzyme involved in the testicular and hepatic sulfoconjugation of steroids such as dehydroepiandrosterone (DHEA) and potentially androstenone. This latter steroid is a major cause of boar taint, which is an unpleasant off-odour and off-flavour in pork from male pigs. Sulfotransferase 2B1 (pSULT2B1) may also be important, although no direct evidence exists for its involvement in sulfoconjugation of steroids. The purpose of this study was to investigate the sulfoconjugation activity of human and porcine sulfotransferases towards DHEA and androstenone...
May 21, 2018: Steroids
https://www.readbyqxmd.com/read/29792821/exhaustive-exercise-induced-oxidative-stress-alteration-of-erythrocyte-oxygen-release-capacity
#15
Yanlian Xiong, Yanlei Xiong, Yueming Wang, Yajin Zhao, Yaojin Li, Yang Ren, Ruofeng Wang, Mingzi Zhao, Yitong Hao, Haibei Liu, Xiang Wang
The aim of the present study is to explore the effect of exhaustive running exercise (ERE) in the oxygen release capacity of rat erythrocytes. Rats were divided into sedentary control (C), moderate running exercise (MRE) and exhaustive running exercise groups. The thermodynamics and kinetics properties of the erythrocyte oxygen release process of different groups were tested. We also determined the degree of band-3 oxidative and phosphorylation, anion transport activity and carbonic anhydrase isoform II(CAII) activity...
May 24, 2018: Canadian Journal of Physiology and Pharmacology
https://www.readbyqxmd.com/read/29792818/substrate-induced-formation-of-ribosomal-decoding-center-for-accurate-and-rapid-genetic-code-translation
#16
Michael Y Pavlov, Måns Ehrenberg
Accurate translation of genetic information is crucial for synthesis of functional proteins in all organisms. We use recent experimental data to discuss how induced fit affects accuracy of initial codon selection on the ribosome by aminoacyl transfer RNA in ternary complex ( T3 ) with elongation factor Tu (EF-Tu) and guanosine-5'-triphosphate (GTP). We define actual accuracy ([Formula: see text]) of a particular protein synthesis system as its current accuracy and the effective selectivity ([Formula: see text]) as [Formula: see text] in the limit of zero ribosomal binding affinity for T3 ...
May 20, 2018: Annual Review of Biophysics
https://www.readbyqxmd.com/read/29792806/fate-of-fluorescence-labels-their-adsorption-and-desorption-kinetics-to-silver-nanoparticles
#17
Claudia Kästner, Linda Böhmert, Albert Braeuning, Alfonso Lampen, Andreas F Thünemann
Silver nanoparticles are among the most widely used und produced nanoparticles. Due to their frequent application in consumer products, the assessment of their toxicological potential has seen a renewed importance. A major difficulty is the traceability of nanoparticles in in vitro and in vivo experiments. Even if the particles are labeled, for example by a fluorescent marker, the dynamic exchange of ligands often prohibits their spatial localization. Our study provides an insight into the adsorption and desorption kinetics of two different fluorescent labels on silver nanoparticles with a core radius of 3 nm by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS) and fluorescence spectroscopy...
May 24, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29792795/tuning-the-morphology-of-nanostructured-peptide-films-by-introduction-of-a-secondary-structure-conformational-constraint-a-case-study-of-hierarchical-self-assembly
#18
Marta De Zotti, Beatrice Muzzi, Emanuela Gatto, Benedetta Di Napoli, Claudia Mazzuca, Antonio Palleschi, Ernesto Placidi, Fernando Formaggio, Claudio Toniolo, Mariano Venanzi
Peptide self-assembly is ubiquitous in nature. It governs the organization of proteins, controlling their folding kinetics and preserving their structure stability and bioactivity. In this connection, model oligopeptides may give important insights on the molecular mechanisms and elementary forces driving the formation of supramolecular structures. In this contribution we show that a single residue substitution, i.e. Aib (α-aminoisobutyric acid) in place of Ala at position 4 of an -(L-Ala)5- homo-oligomer, strongly alters the aggregation process...
May 24, 2018: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29792689/selectivity-within-a-family-of-bacterial-phosphothreonine-lyases
#19
Kaitlin A Chambers, Nile S Abularrage, Rebecca A Scheck
Phosphothreonine lyases are bacterial effector proteins secreted into host cells to facilitate the infection process. This enzyme family catalyzes an irreversible elimination reaction that converts phosphothreonine or phosphoserine to dehydrobutyrine or dehydroalanine, respectively. Herein we report a study of substrate selectivity for each of the four known phosphothreonine lyases. This was accomplished using a combination of mass spectrometry and enzyme kinetics assays for a series of phosphorylated peptides derived from the mitogen activated protein kinase (MAPK) activation loop...
May 24, 2018: Biochemistry
https://www.readbyqxmd.com/read/29792667/control-of-selectivity-in-palladium-ii-catalyzed-oxidative-transformations-of-allenes
#20
Bin Yang, Youai Qiu, Jan-E Bäckvall
Oxidation reactions play a central role in organic synthesis, and it is highly desirable that these reactions are mild and occur under catalytic conditions. In Nature, oxidation reactions occur under mild conditions via cascade processes, and furthermore, they often occur in an enantioselective manner with many of them involving molecular oxygen or hydrogen peroxide as the terminal oxidant. Inspired by the reactions in Nature, we have developed a number of Pd(II)-catalyzed cascade reactions under mild oxidative conditions...
May 24, 2018: Accounts of Chemical Research
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