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https://www.readbyqxmd.com/read/28816438/interfacial-mechanisms-of-water-vapor-sorption-into-cellulose-nanofibril-films-as-revealed-by-quantitative-models
#1
Minna Hakalahti, Marco Faustini, Cédric Boissière, Eero Kontturi, Tekla Tammelin
Humidity is an efficient instrument for facilitating changes in local architectures of 2-dimensional surfaces assembled from nanoscaled biomaterials. Here, complementary surface-sensitive methods are used to collect explicit and precise experimental evidence on the water vapor sorption into (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidized cellulose nanofibril (CNF) thin film over the relative humidity (RH) range from 0 to 97%. Changes in thickness and mass of the film due to water vapor uptake are tracked using Spectroscopic Ellipsometry and Quartz Crystal Microbalance with Dissipation monitoring, respectively...
August 17, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/28816429/smart-cellulose-nanofluids-produced-by-tunable-hydrophobic-association-of-polymer-grafted-cellulose-nanocrystals
#2
Yea Ram Lee, Daehwan Park, Sang Koo Choi, Miju Kim, Heung Soo Baek, Jin Nam, Chan Bok Chung, Chinedum O Osuji, Jin Woong Kim
Cellulose fibrils, unique plant-derived semi-crystalline nanomaterials with exceptional mechanical properties, have significant potential for rheology modification of complex fluids due to their ability to form a physically associated semi-flexible fibrillary network. Here, we report new associative cellulose nanocrystals (ACNCs) with stress-responsive rheological behaviors in an aqueous solution. The surface-mediated living radical polymerization was employed to graft poly (stearyl methacrylate-co-2-methacryloxyethyl phosphorylcholine) brushes onto the nanofibrils, and then 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation was conducted to produce nanoscale ACNCs in the aqueous solution...
August 17, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28815766/preparation-of-robust-metal-free-magnetic-nanoemulsions-encapsulating-low-molecular-weight-nitroxide-radicals-and-hydrophobic-drugs-directed-toward-mri-visible-targeted-delivery
#3
Rui Tamura, Kota Nagura, Yusa Takemoto, Satori Moronaga, Yoshiaki Uchida, Satoshi Shimono, Akihiko Shiino, Kenji Tanigaki, Tsukuru Amano, Fumi Yoshino, Yohei Noda, Satoshi Koizumi, Naoki Komatsu, Tatsuhisa Kato, Jun Yamauchi
With a view to developing a theranostic nanomedicine for magnetic resonance (MR) imaging-visible targeted drug delivery system, robust metal-free magnetic nanoemulsions (mean particle sizes of less than 20 nm) consisting of the biocompatible surfactant 1 and the incorporated hydrophobic low-molecular-weight 2,2,5-trimethyl-5-(4-alkoxy)phenylpyrrolidine-N-oxyl radicals [(±)-2] have been prepared in pH 7.4 phosphate-buffered saline. The structure of the nanoemulsions has been characterized by electron paramagnetic resonance spectroscopy, and dynamic light scattering and small angle neutron scattering measurements...
August 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28812080/computational-design-of-ph-switchable-control-agents-for-nitroxide-mediated-polymerization
#4
Ganna Gryn'ova, Leesa M Smith, Michelle L Coote
In the present work we use accurate quantum chemistry to evaluate several known and novel nitroxides bearing acid-base groups as pH-switchable control agents for room temperature NMP. Based on G3(MP2,CC)(+)//M06-2X/6-31+G(d) calculations with UAKS-CPCM/M06-2X/6-31+G(d) solvation corrections, a number of novel nitroxides are predicted to be suitable for controlled polymerization of bulk styrene at room temperature when deprotonated (i.e. negatively charged), while remaining inert when neutral. These include an α-ethyl analogue of 3-carboxy-PROXYL and novel derivatives of 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO) that have been modified to include acidic groups...
August 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28805227/landscape-of-the-structure-o-h-bond-dissociation-energy-relationship-of-oximes-and-hydroxylamines
#5
Rina Dao, Xinyu Wang, Kexian Chen, Chenxuan Zhao, Jia Yao, Haoran Li
The relationship between the homolytic O-H bond dissociation enthalpies (BDEs) and the structures of N-oxyl radical precursors (i.e. hydroxylamines and oximes) is important to predict their reactivity. Yet several crucial facts remain hidden to complete the picture such as the substituent electronic effects on the BDEs of oximes. In this work, the O-H BDEs of 120 hydroxylamines and 120 oximes have been calculated. It was found that the majority of the iminoxyl radicals are σ radicals, except for some π radicals...
August 14, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28769823/elevated-carbon-dioxide-alleviates-aluminum-toxicity-by-decreasing-cell-wall-hemicellulose-in-rice-oryza-sativa
#6
Xiao Fang Zhu, Xu Sheng Zhao, Bin Wang, Qi Wu, Ren Fang Shen
Carbon dioxide (CO2) is involved in plant growth as well as plant responses to abiotic stresses; however, it remains unclear whether CO2 is involved in the response of rice (Oryza sativa) to aluminum (Al) toxicity. In the current study, we discovered that elevated CO2 (600 μL·L(-1)) significantly alleviated Al-induced inhibition of root elongation that occurred in ambient CO2 (400 μL·L(-1)). This protective effect was accompanied by a reduced Al accumulation in root apex. Al significantly induced citrate efflux and the expression of OsALS1, but elevated CO2 had no further effect...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28766325/c-h-activation-from-iron-ii-nitroxido-complexes
#7
Theodore Alexander Betley, Claudia Kleinlein, Andrew J Bendelsmith, Shao-Liang Zheng
The reaction of nitroxyl radicals TEMPO (2,2',6,6'-tetramethylpiperidinyloxyl) and AZADO (2-azaadamantane-N-oxyl) with an iron(I) synthon affords iron(II) nitroxido complexes (ArL)Fe(κ1-TEMPO) and (ArL)Fe(κ2-N,O-AZADO) (ArL = 1,9-(2,4,6-Ph3C6H2)2-5-mesityldipyrromethene). Both high-spin iron(II) nitroxido species are stable in the absence of weak C-H bonds, but decay via N-O bond homolysis to ferrous or ferric iron hydroxides in the presence of 1,4-cyclohexadiene. Whereas (ArL)Fe(κ1-TEMPO) reacts to give a diferrous hydroxide [(ArL)Fe]2(µ-OH)2, the reaction of four-coordinate (ArL)Fe(κ2-N,O-AZADO) with hydrogen atom donors yields ferric hydroxide (ArL)Fe(OH)(AZAD)...
August 1, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28758976/astragalosidic-acid-a-new-water-soluble-derivative-of-astragaloside-iv-prepared-using-remarkably-simple-tempo-mediated-oxidation
#8
Lin-Sen Qing, Shu-Lin Peng, Jian Liang, Li-Sheng Ding
There is an urgent need for a water-soluble derivative of astragaloside IV for drug R&D. In the present study, a remarkably simple method for the preparation of such a water-soluble derivative of astragaloside IV has been developed. This protocol involves oxidative 2,2,6,6-tetramethylpiperidine-1-oxyl free radical (TEMPO)-mediated transformation of astragaloside IV to its carboxylic acid derivative, which is a new compound named astragalosidic acid. The structure of astragalosidic acid was elucidated by means of spectroscopic analysis...
July 31, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28731345/asymmetric-%C3%AE-sulfonyl-and-%C3%AE-phosphoryl-oxylation-of-ketones-by-a-chiral-hypervalent-iodine-iii
#9
Guillaume Levitre, Audrey Dumoulin, Pascal Retailleau, Armen Panossian, Frédéric R Leroux, Géraldine Masson
An enantioselective direct oxygenation of propiophenone derivatives mediated by a catalytic or stoichiometric amount of new chiral non-C2-symmetric iodoarenes(III) is reported. The reaction gives an easy entry to optically active α-sulfonyl- and α-phosphoryl oxyketones in respectable yields and enantioselectivities.
July 31, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28714295/one-step-cationic-grafting-of-4-hydroxy-tempo-and-its-application-in-a-hybrid-redox-flow-battery-with-a-crosslinked-pbi-membrane
#10
Zhenjun Chang, Dirk Henkensmeier, Ruiyong Chen
By using a one-step epoxide ring-opening reaction between 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-hydroxy-TEMPO) and glycidyltrimethylammonium cation (GTMA+), we synthesize a cation-grafted TEMPO (g+-TEMPO) and study its electrochemical performance against a Zn2+/Zn anode in a hybrid redox flow battery. To conduct Cl- counter anions, a crosslinked methylated polybenzimidazole (PBI) membrane was prepared and placed between the catholyte and anolyte. Compared to 4-hydroxy-TEMPO, the positively charged g+-TEMPO exhibits enhanced reaction kinetics...
July 17, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28706529/bacillus-licheniformis-sa03-confers-increased-saline-alkaline-tolerance-in-chrysanthemum-plants-by-induction-of-abscisic-acid-accumulation
#11
Cheng Zhou, Lin Zhu, Yue Xie, Feiyue Li, Xin Xiao, Zhongyou Ma, Jianfei Wang
Soil saline-alkalization is a major abiotic stress that leads to low iron (Fe) availability and high toxicity of sodium ions (Na(+)) for plants. It has recently been shown that plant growth promoting rhizobacteria (PGPR) can enhance the ability of plants to tolerate multiple abiotic stresses such as drought, salinity, and nutrient deficiency. However, the possible involvement of PGPR in improving saline-alkaline tolerance of plants and the underlying mechanisms remain largely unknown. In this study, we investigated the effects of Bacillus licheniformis (strain SA03) on the growth of Chrysanthemum plants under saline-alkaline conditions...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28698982/targeting-the-reactive-intermediate-in-polysaccharide-monooxygenases
#12
Erik D Hedegård, Ulf Ryde
Lytic polysaccharide monooxygenases (LPMOs) are copper metalloenzymes that can enhance polysaccharide depolymerization through an oxidative mechanism, making them interesting for the production of biofuel from cellulose. However, the details of this activation are unknown; in particular, the nature of the intermediate that attacks the glycoside C-H bond in the polysaccharide is not known, and a number of different species have been suggested. The homolytic bond-dissociation energy (BDE) has often been used as a descriptor for the bond-activation power, especially for inorganic model complexes...
July 11, 2017: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/28692104/c-on-bond-homolysis-of-alkoxyamines-when-too-high-polarity-is-detrimental
#13
Paulin Nkolo, Gérard Audran, Raphael Bikanga, Paul Brémond, Sylvain R A Marque, Valérie Roubaud
Throughout the last decade, the effect of electron withdrawing groups (EWGs) has been known to play a role - minor or moderate depending on the nitroxyl fragment R1R2NO - in the change in the homolysis rate constant (kd) for C-ON bond homolysis in alkoxyamines (R1R2NOR). It has been shown that the effect of EWGs on kd is described by a linear relationship with the electrical Hammett constant σI. Since then, linear multi-parameter relationships f(σRS,ν,σI) have been developed to account for the effects involved in the changes in kd, which are the stabilization of the released radical (σRS) and the bulkiness (ν) and polarity (σI) of the alkyl fragment...
July 26, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28689421/2-phenyl-4-4-5-5-tetramethylimidazoline-1-oxyl-3-oxide-ptio-%C3%A2-radical-scavenging-a-new-and-simple-antioxidant-assay-in-vitro
#14
Xican Li
Current in vitro antioxidant assays have several limitations, which frequently cause inconsistent results. The study develops a new antioxidant assay using the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO(•)). After the investigation of various factors, the experimental protocol was briefly recommended as follows: PTIO(•) and the sample solution were added to phosphate buffer (pH 7.4, 50 mM), incubated at 37 °C for 2 h, and then spectrophotometrically measured at 557 nm. The validation test based on 20 pure compounds and 30 lyophilized aqueous extracts suggested that PTIO(•) scavenging had a good linear relationship, stability, and reproducibility...
August 2, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28665342/exogenous-feeding-of-fructose-and-phenylalanine-further-improves-betulin-production-in-suspended-betula-platyphylla-cells-under-nitric-oxide-treatment
#15
Guizhi Fan, Tingting Nie, Jin Sheng Fan, Yaguang Zhan
The aim of this study was to assay by NMR the metabolites which contribute to betulin production. 8-day-old suspended birch (Betula platyphylla) cells were treated by sodium nitroprusside (SNP) treatment, an NO donor, and 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (cPTIO), an NO-specific scavenger. The results showed that betulin production was increased by five times after SNP treatment, similar with that of the control under cPTIO treatment. Forty one metabolites were detected after SNP treatment or cPTIO treatment...
June 30, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28657581/bacillus-amyloliquefaciens-say09-increases-cadmium-resistance-in-plants-by-activation-of-auxin-mediated-signaling-pathways
#16
Cheng Zhou, Lin Zhu, Zhongyou Ma, Jianfei Wang
Without physical contact with plants, certain plant growth-promoting rhizobacteria (PGPR) can release volatile organic compounds (VOCs) to regulate nutrient acquisition and induce systemic immunity in plants. However, whether the PGPR-emitted VOCs can induce cadmium (Cd) tolerance of plants and the underlying mechanisms remain elusive. In this study, we probed the effects of Bacillus amyloliquefaciens (strain SAY09)-emitted VOCs on the growth of Arabidopsis plants under Cd stress. SAY09 exposure alleviates Cd toxicity in plants with increased auxin biosynthesis...
June 28, 2017: Genes
https://www.readbyqxmd.com/read/28655813/neurovascular-unit-protection-from-cerebral-ischemia-reperfusion-injury-by-radical-containing-nanoparticles-in-mice
#17
Hisayuki Hosoo, Aiki Marushima, Yukio Nagasaki, Aki Hirayama, Hiromu Ito, Sandra Puentes, Arnela Mujagic, Hideo Tsurushima, Wataro Tsuruta, Kensuke Suzuki, Hirofumi Matsui, Yuji Matsumaru, Tetsuya Yamamoto, Akira Matsumura
BACKGROUND AND PURPOSE: Reperfusion therapy by mechanical thrombectomy is used to treat acute ischemic stroke. However, reactive oxygen species generation after reperfusion therapy causes cerebral ischemia-reperfusion injury, which aggravates cerebral infarction. There is limited evidence for clinical efficacy in stroke for antioxidants. Here, we developed a novel core-shell type nanoparticle containing 4-amino-4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (nitroxide radical-containing nanoparticles [RNPs]) and investigated its ability to scavenge reactive oxygen species and confer neuroprotection...
August 2017: Stroke; a Journal of Cerebral Circulation
https://www.readbyqxmd.com/read/28636313/iodine-iii-reagents-in-radical-chemistry
#18
Xi Wang, Armido Studer
The chemistry of hypervalent iodine(III) compounds has gained great interest over the past 30 years. Hypervalent iodine(III) compounds show valuable ionic reactivity due to their high electrophilicity but also express radical reactivity as single electron oxidants for carbon and heteroatom radical generation. Looking at ionic chemistry, these iodine(III) reagents can act as electrophiles to efficiently construct C-CF3, X-CF3 (X = heteroatom), C-Rf (Rf = perfluoroalkyl), X-Rf, C-N3, C-CN, S-CN, and C-X bonds...
July 18, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28621375/roles-of-phenol-groups-and-auxiliary-ligand-of-copper-ii-complexes-with-tetradentate-ligands-in-the-aerobic-oxidation-of-benzyl-alcohol
#19
Guangli Zhan, Wei Zhong, Zhenhong Wei, Zhenzhen Liu, Xiaoming Liu
Herein, six copper(ii) complexes with multidentate ligands, [Cu(HL1)(OAc)(HOAc)] (1), [Cu(HL2)(OAc)] (2), [Cu(HL3)(OAc)] (3), [CuL4(OAc)] (4), [Cu(HL2)Cl] (5), and [Cu(HL3)Cl] (6) {H2L1 = [bis(3-tert-butyl-2-hydroxybenzyl)](2-pyridylmethyl)amine, H2L2 = [(3-tert-butyl-2-hydoxybenzyl)(3-trifluoromethyl-2-hydroxybenzyl) (2-pyridylmethyl)]amine, H2L3 = [bis(3-trifluoromethyl-2-hydroxybenzyl)] (2-pyridylmethyl)amine, and HL4 = [bis(2-pyridylmethyl)] (3-tert-butyl-2-hydroxybenzyl)amine}, are reported. The complexes were characterized by UV-vis spectroscopy, high-resolution mass spectrometry, X-ray single-crystal diffraction analysis and electrochemistry...
June 27, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28609611/selective-aliphatic-carbon-carbon-bond-activation-by-rhodium-porphyrin-complexes
#20
Ching Tat To, Kin Shing Chan
The carbon-carbon bond activation of organic molecules with transition metal complexes is an attractive transformation. These reactions form transition metal-carbon bonded intermediates, which contribute to fundamental understanding in organometallic chemistry. Alternatively, the metal-carbon bond in these intermediates can be further functionalized to construct new carbon-(hetero)atom bonds. This methodology promotes the concept that the carbon-carbon bond acts as a functional group, although carbon-carbon bonds are kinetically inert...
June 13, 2017: Accounts of Chemical Research
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