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Kaitao Zhang, Minggui Shen, He Liu, Shibin Shang, Dan Wang, Henrikki Liimatainen
Cellulose nanofibrils (CNFs) were firstly prepared by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation and further oxidized to 2,3-dialdehyde nanocelluloses (DANCs) by periodate oxidation. Furthermore, by using DANCs as reducing as well as stabilizing agent, palladium (Pd) and gold (Au) nanoparticles (NPs) supported on nanocellulose (PdNPs@NC and AuNPs@NC) were synthesized, respectively. The reduction of Pd or Au ions to its metallic form by DANCs was confirmed by UV-vis spectra, XRD, and XPS. TEM results showed that Pd and Au NPs were homogenously deposited onto cellulose nanofibrils, respectively...
April 15, 2018: Carbohydrate Polymers
Carlos D S Silva, Iury A Paz, Felipe D Abreu, Aurideia P de Sousa, Carla P Veríssimo, Nilberto R F Nascimento, Tércio F Paulo, Davila Zampieri, Marcos N Eberlin, Ana C S Gondim, Loraine C Andrade, Idalina M M Carvalho, Eduardo H S Sousa, Luiz G F Lopes
Nitric oxide has been involved in many key biological processes such as vasodilation, platelet aggregation, apoptosis, memory function, and this has drawn attention to the development of exogenous NO donors. Metallonitrosyl complexes are an important class of these compounds. Here, two new ruthenium nitrosyl complexes containing a thiocarbonyl ligand, with the formula cis-[Ru(phen) 2 (L)(NO)](PF 6 ) 3 (phen = phenantroline, L = thiourea or thiobenzamide), were synthesized and characterized by electronic spectroscopy, FTIR, NMR , mass spectrometry and voltammetric techniques...
February 9, 2018: Journal of Inorganic Biochemistry
Markus Griesser, Ron Shah, Antonius T Van Kessel, Omkar Zilka, Evan A Haidasz, Derek A Pratt
Sterically-hindered nitroxides such as 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) have long been ascribed antioxidant activity that is thought to underlie their chemopreventive and anti-aging properties. However, the most commonly invoked reactions in this context - combination with an alkyl radical to give a redox inactive alkoxyamine or the catalysis of superoxide dismutation - are unlikely to be relevant under (most) physiological conditions. Herein we characterize the kinetics and mechanisms of the reactions of TEMPO, as well as an N-arylnitroxide and a N,N-diarylnitroxide, with alkylperoxyl radicals, the propagating species in lipid peroxidation...
February 16, 2018: Journal of the American Chemical Society
Nilesh R Kamble, Snorri Th Sigurdsson
A series of purine-based spin labels was prepared for noncovalent spin-labeling of abasic sites of duplex nucleic acids through hydrogen bonding to an orphan base on the opposing strand and π-stacking interactions with the flanking bases. Both 1,1,3,3-tetramethylisoindolin-2-yloxyl and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) were conjugated to either the C2- or C6-position of the purines, yielding nitroxide derivatives of guanine, adenine, or 2,6-diaminopurine. The isoindoline-derived spin labels showed extensive or full binding to abasic sites in RNA duplexes, whereas the TEMPO-derived spin labels showed limited binding...
February 16, 2018: Chemistry: a European Journal
Meng Zhao, Yijie Zhou, Shuyun Liu, Lan Li, Younan Chen, Jingqiu Cheng, Yanrong Lu, Jingping Liu
Persistent mitochondrial injury occurs after acute kidney injury (AKI) and mitochondria-targeted antioxidant Mito-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) (MT) has shown benefits for AKI, but its efficiency is limited by short half-life and side effect in vivo. Self-assembling peptide (SAP) hydrogel is a robust platform for drug delivery. This study aims to develop an SAP-based carrier to slow release MT for enhancing its long-term therapeutic potency on AKI. The KLD with aspartic acid (KLDD) was designed...
November 2018: Drug Delivery
Hendrik Woehlk, Jan Steinkoenig, Christiane Lang, Lukas Michalek, Vanessa Trouillet, Peter Krolla-Sidenstein, Anja S Goldmann, Leonie Barner, James P Blinco, Christopher Barner-Kowollik, Kathryn E Fairfull-Smith
We pioneer a versatile surface modification strategy based on mussel inspired oxidative catecholamine polymerization for the design of nitroxide containing thin polymer films. A 3,4-dihydroxy-L-phenylalanine (L-DOPA) monomer equipped with a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derived oxidation-labile hydroxylamine functional group is employed as a universal coating agent to generate polymer scaffolds with persistent radical character. Various types of materials including silicon, titanium, ceramic alumina and inert poly(tetrafluoroethylene) (PTFE) were successfully coated with poly(DOPA-TEMPO) thin films in a one-step dip-coating procedure under aerobic, slightly alkaline (pH 8...
February 14, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Shogo Miyashiro, Tomoaki Ishii, Youhei Miura, Naoki Yoshioka
A nitronyl nitroxide derivative, 2-phenylethynyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl-3-oxide (1), and two verdazyl derivatives carrying a phenylacetylene unit, 1,5-diphenyl-3-phenylethynyl-6-oxo-1,2,4,5-tetrazin-2-yl (2) and 1,5-diisopropyl-3-phenylethynyl-6-oxo-1,2,4,5-tetrazin-2-yl (3), were synthesized and their packing structures were studied by X-ray crystallographic analysis and magnetically characterized in the solid state. While 1 and 3 had an isolated doublet spin state, 2 formed an antiferromagnetically coupled pair (2J/kB = -118 K)...
February 9, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Hongdao Li, Juan Sun, Meng Yang, Zan Sun, Jinkui Tang, Yue Ma, Licun Li
Functionalized nitronyl nitroxide biradical ligands incorporating pyridine groups hold CoII and LnIII ions together, creating biradical-based 3d-4f tetranuclear complexes [Ln2Co2(hfac)10(NITPhPybis)2] [LnIII = Gd (1), Tb (2), Dy (3), and Ho (4); NITPhPybis = 5-(4-pyridyl)-1,3-bis(1'-oxyl-3'-oxido-4',4',5',5'-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene; hfac = hexafluoroacetylacetonate]. These complexes have a centrosymmetric cyclic molecular structure in which two biradicals perform as tetradentate ligands to bind two CoII and two LnIII ions, resulting in a rare octaspin system...
February 8, 2018: Inorganic Chemistry
Hailey A Houson, Gregory N Nkepang, Andria F Hedrick, Vibhudutta Awasthi
Positron emission tomography (PET) of myocardial infarction (MI) by infarct avid imaging has the potential to reduce the time to diagnosis and improve diagnostic accuracy. The objective of this work was to synthesize 18 F-labeled glucaric acid (FGA) for PET imaging of isoproterenol-induced cardiomyopathy in a rat model. METHODS: We synthesized 18 F-FGA by controlled oxidation of 18 F-fluorodeoxy glucose (FDG), mediated by 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in presence of NaBr and NaOCl in highly-buffered reaction conditions...
December 27, 2017: Nuclear Medicine and Biology
Hong Xie, Xican Li, Zhenxing Ren, Weimin Qiu, Jianlan Chen, Qian Jiang, Ban Chen, Dongfeng Chen
Tibetan tea (Kangzhuan) is an essential beverage of the Tibetan people. In this study, a lyophilized aqueous extract of Tibetan tea (LATT) was prepared and analyzed by HPLC. The results suggested that there were at least five phenolic components, including gallic acid, and four catechins (i.e., (+)-catechin, (-)-catechin gallate (CG), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate). Gallic acid, the four catechins, and LATT were then comparatively investigated by four antioxidant assays: ferric reducing antioxidant power, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•) scavenging, 1,1-diphenyl-2-picryl-hydrazl radical scavenging, and 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) radical scavenging assays...
January 24, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Chaofeng Zhang, Zhipeng Huang, Jianmin Lu, Nengchao Luo, Feng Wang
Generation of controllable carbon radical under the assistance of N-oxyl radical is an efficient method for the activation of C-H bonds in hydrocarbons. We herein report that irradiation of α-Fe2O3 and N-hydroxyphthalimide (NHPI) under 455 nm light generates phthalimide-N-oxyl radical (PINO*), which after being formed by oxidation with holes, is confined on α-Fe2O3 surface. The half-life time of the confined radical reaches 22 seconds as measured by in situ electron paramagnetic resonance (EPR) after the light being turned off...
January 24, 2018: Journal of the American Chemical Society
Chun-Nan Wu, Shih-Chang Fuh, Shin-Ping Lin, Yen-Yi Lin, Hung-Yueh Chen, Jui-Ming Liu, Kuan-Chen Cheng
Biocompatible bacterial cellulose pellicle (BCP) is a candidate for biomedical material such as wound dressing. However, due to lack of antibacterial activity, to grant BCP with the property is crucial for its biomedical application. In the present study, BCP was modified by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation using TEMPO/NaClO/NaBr system at pH 10 to form TEMPO-oxidized BCP (TOBCP) with anionic C6 carboxylate groups. The TOBCP was subsequently ion-exchanged in AgNO3 solution and silver nanoparticles (AgNP) with diameter of ~16...
January 15, 2018: Biomacromolecules
Papitchaya Srithep, Preeyaporn Pornkulwat, Tawan Limpiyakorn
In this study, two laboratory nitrifying reactors (NRI and NRII), which were seeded by sludge from different sources and operated under different operating conditions, were found to possess distinct dominant ammonia-oxidizing microorganisms. Ammonia-oxidizing archaeal (AOA) amoA genes outnumbered ammonia-oxidizing bacterial (AOB) amoA genes in reactor NRI, while only AOB amoA genes were detectable in reactor NRII. The AOA amoA gene sequences retrieved from NRI were characterized within the Nitrososphaera sister cluster of the group 1...
January 10, 2018: Environmental Science and Pollution Research International
Wen-Cheng Liu, Si-Qiu Zheng, Zhen-Dong Yu, Xiang Gao, Ran Shen, Ying-Tang Lu
While nitric oxide (NO) is known to regulate root growth, the factor(s) modulating NO during this process have not yet been elucidated. Here, we identified Arabidopsis WD40-REPEAT 5a (WDR5a) as a novel factor that functions in root growth by modulating NO accumulation. The wdr5a-1 mutant accumulated less NO and produced longer roots than the wild type, while the WDR5a overexpression lines had the opposite phenotype. The role of NO was further supported by our observation that the NO donor sodium nitroprusside (SNP) and the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) rescued the root meristem growth phenotypes of the wdr5a-1 and WDR5a overexpression lines, respectively...
January 6, 2018: Plant Journal: for Cell and Molecular Biology
Kaitlyn Beyfuss, David A Hood
BACKGROUND: p53 is a tumor suppressor protein involved in regulating a wide array of signaling pathways. The role of p53 in the cell is determined by the type of imposed oxidative stress, its intensity and duration. The last decade of research has unravelled a dual nature in the function of p53 in mediating the oxidative stress burden. However, this is dependent on the specific properties of the applied stress and thus requires further analysis. METHODS: A systematic review was performed following an electronic search of Pubmed, Google Scholar, and ScienceDirect databases...
January 3, 2018: Redox Report: Communications in Free Radical Research
Yaxin Zhou, Tsuguyuki Saito, Lennart Bergström, Akira Isogai
Softwood bleached kraft pulp (SBKP) and microcrystalline cellulose (MCC) were oxidized using a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated system. The TEMPO-oxidized SBKP prepared with 10 mmol/g NaClO (SBKP-10) had a higher mass recovery ratio and higher carboxylate content than the other prepared celluloses including the TEMPO-oxidized MCCs. The SBKP-10 was then exposed to cavitation-induced forces through sonication in water for 10-120 min to prepare aqueous dispersions of needle-like TEMPO-oxidized cellulose nanocrystals (TEMPO-CNCs) with homogenous width of 3...
December 28, 2017: Biomacromolecules
Jian-An Xian, Xiu-Xia Zhang, An-Li Wang, Jun-Tao Li, Pei-Hua Zheng, Yao-Peng Lu, Dong-Mei Wang, Jian-Min Ye
Oxidative burst, release of reactive oxygen species/reactive nitrogen species (ROS/RNS) contributed to microorganisms killing, is a vital immune response of crustacean haemocyte. Three morphologic haemocyte types (hyaline cells, HC; semigranular cells, SGC; granular cells, GC) have been defined in crustaceans, and found to play different roles in immune defense. However, oxidative burst activities of different haemocyte subpopulations in crustaceans are currently not documented. In the present study, we investigated the oxidative burst activities of the three haemocyte types in the freshwater prawn Macrobrachium rosenbergii using the common ROS fluorescent probe dichlorofluorescin-diacetate (DCFH-DA)...
December 22, 2017: Fish & Shellfish Immunology
Yuta Hori, Yoshihito Shiota, Tomokazu Tsuji, Masahito Kodera, Kazunari Yoshizawa
A dicopper(II) complex, [Cu2(μ-OH)(6-hpa)]3+, where 6-hpa is 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane, generates an oxyl radical of CuIIO• and catalyzes the selective hydroxylation of benzene to phenol. From the structural similarity to methane activation catalysts (e.g., bare CuO+ ion, Cu-ZSM-5, and particulate methane monooxygenase), it is expected to catalyze methane hydroxylation. The catalytic performance for the hydroxylation of methane to methanol by this dicopper complex is investigated by using density functional theory (DFT) calculations...
December 16, 2017: Inorganic Chemistry
Luca Bertini, Raffaella Breglia, Matteo Lambrughi, Piercarlo Fantucci, Luca De Gioia, Marco Borsari, Marco Sola, Carlo Augusto Bortolotti, Maurizio Bruschi
Lytic polysaccharide monooxygenases (LPMOs) are Cu-containing enzymes that facilitate the degradation of recalcitrant polysaccharides by the oxidative cleavage of glycosidic bonds. They are gaining rapidly increasing attention as key players in biomass conversion, especially for the production of second-generation biofuels. Elucidation of the detailed mechanism of the LPMO reaction is a major step toward the assessment and optimization of LPMO efficacy in industrial biotechnology, paving the way to utilization of sustainable fuel sources...
December 12, 2017: Inorganic Chemistry
Yoshiki Horikawa, Michiko Shimizu, Tsuguyuki Saito, Akira Isogai, Tomoya Imai, Junji Sugiyama
Chara is a genus of freshwater alga that is evolutionarily observed at the aquatic-terrestrial boundary, whose cellulose microfibrils are similar to those of terrestrial plants regarding the crystallinity and biosynthesis of cellulose. Oven-dried and never-dried celluloses samples were prepared from chara. Terrestrial plant cellulose samples were used as references. The lengths and length distributions of oven-dried and never-dried chara cellulose microfibrils after acid hydrolysis with or without pretreatment by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, which was used for efficient fibrillation of acid-hydrolyzed products, were observed by transmission electron microscopy...
December 7, 2017: International Journal of Biological Macromolecules
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