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Proton and carbon

Young Jin Sa, Dong-Jun Seo, Jinwoo Woo, Jung Tae Lim, Jae Yeong Cheon, Seung Yong Yang, Jae Myeong Lee, Dongwoo Kang, Tae Joo Shin, Hyeon Suk Shin, Hu Young Jeong, Chul Sung Kim, Min Gyu Kim, Tae-Young Kim, Sang Hoon Joo
Iron-nitrogen on carbon (Fe-N/C) catalysts have emerged as promising non-precious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in energy conversion and storage devices. It has been widely suggested that an active site structure for Fe-N/C catalysts contains Fe-Nx coordination. However, the preparation of high-performance Fe-N/C catalysts mostly involves a high-temperature pyrolysis step, which generates not only catalytically active Fe-Nx sites, but also less active large iron-based particles...
October 18, 2016: Journal of the American Chemical Society
Yves Claude Guillaume, Lydie Lethier, Claire André
TRAIL is a member of the TNF family of cytokines which induces apoptosis of cancer cells via its binding to its cognate receptors, DR5 a high affinity site and DR4 a site of low affinity. Our working group has recently demonstrated that nanovectorization of TRAIL with single wall carbon nanotubes (abbreviated NPT) enhanced TRAIL affinity to the high affinity site DR5 and increased pro apoptotic potential in different human tumor cell lines. In this paper, the DR4 low affinity site was immobilized on a chromatographic support and the effect of temperature on a wide temperature range 1°C-50°C was studied to calculate the thermodynamic parameters of the binding of TRAIL and NPT to DR4 and DR5 receptors...
October 12, 2016: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
George F Reiter, Aniruddha Deb, Yoshiharu Sakurai, Masayoshi Itou, Alexander I Kolesnikov
X-ray Compton scattering measurements of the electron momentum distribution in water confined in both single walled and double walled carbon nanotubes (SWNT and DWNT), as a function of temperature and confinement size, presented here, together with earlier measurements of the proton momentum distribution in the same systems, using neutron Compton scattering, provide a coherent picture of an anomalous state of water that exists because of nano-confinement. This state cannot be described by the weakly interacting molecule picture...
October 17, 2016: Journal of Physical Chemistry Letters
Amelia Pollard, Freya Shephard, James Freed, Susan Liddell, Lisa Chakrabarti
Carbonic anhydrase inhibitors are used to treat glaucoma and cancers. Carbonic anhydrases perform a crucial role in the conversion of carbon dioxide and water into bicarbonate and protons. However, there is little information about carbonic anhydrase isoforms during the process of ageing. Mitochondrial dysfunction is implicit in ageing brain and muscle. We have interrogated isolated mitochondrial fractions from young adult and middle aged mouse brain and skeletal muscle. We find an increase of tissue specific carbonic anhydrases in mitochondria from middle-aged brain and skeletal muscle...
October 10, 2016: Aging
Jie Hao, Tongfang Xiao, Fei Wu, Ping Yu, Lanqun Mao
In vivo monitoring of pH in live brain remains very essential to understanding acid-base chemistry in various physiological processes. This study demonstrates a potentiometric method for in vivo monitoring of pH in the central nervous system with carbon fiber-based proton-selective electrodes (CF-H+ISEs) with high anti-fouling property. The CF-H+ISEs are prepared by formation of a H+-selective membrane (H+ISM) with polyvinyl chloride polymeric matrixes containing plasticizer bis(2-ethylhexyl)sebacate, H+ ionophore tridodecylamine, and ion exchanger potassium tetrakis(4-chlorophenyl)borate onto carbon fiber electrodes (CFEs)...
October 14, 2016: Analytical Chemistry
Junjie Li, Alexander B Pacheco, Krishnan Raghavachari, Srinivasan S Iyengar
We probe the structure, stability and vibrational properties of the fundamental C2H3(+) carbocation that exists with preference in a bridged hydrogen conformation. Our computational study includes electronic structure treatment, incorporation of nuclear motion through classical and quantum paradigms, the effect of temperature, and the associated sampling of the potential surface, and the effect of single H/D isotopic substitution (i.e., C2H2D(+)). We find that while the non-classical, "Bridged" isomer is most stable, the "Classical" form does have a small presence under ambient conditions since the zero point level straddles the barrier between the Classical and Bridged isomers in a reduced dimensional analysis of the Bridged ↔ Classical transfer coordinate...
October 13, 2016: Physical Chemistry Chemical Physics: PCCP
Gilbert J Choi, Qilei Zhu, David C Miller, Carol J Gu, Robert R Knowles
Despite advances in hydrogen atom transfer (HAT) catalysis, there are currently no molecular HAT catalysts that are capable of homolysing the strong nitrogen-hydrogen (N-H) bonds of N-alkyl amides. The motivation to develop amide homolysis protocols stems from the utility of the resultant amidyl radicals, which are involved in various synthetically useful transformations, including olefin amination and directed carbon-hydrogen (C-H) bond functionalization. In the latter process-a subset of the classical Hofmann-Löffler-Freytag reaction-amidyl radicals remove hydrogen atoms from unactivated aliphatic C-H bonds...
October 12, 2016: Nature
Haleh Hashemi Haeri, Philipp Spindler, Jörn Plackmeyer, Thomas Prisner
Carbon-centered radicals are interesting alternatives to otherwise commonly used nitroxide spin labels for dipolar spectroscopy techniques because of their narrow ESR linewidth. Herein, we present a novel BDPA biradical, where two BDPA (α,α,γ,γ-bisdiphenylene-β-phenylallyl) radicals are covalently tethered by a saturated biphenyl acetylene linker. The inter-spin distance between the two spin carrier fragments was measured using double quantum coherence (DQC) ESR methodology. The DQC experiment revealed a mean distance of only 1...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Mina Mozafari, Jean-Claude Brodovitch, Lalangi Chandrasena, Paul Walter Percival
In addition to their importance as abundant hydrocarbon deposits in nature, clathrate hydrates are being studied as potential media for hydrogen and carbon dioxide storage, and as "nano-reactors" for small molecules. However, little is known about the behaviour of reactive species in such materials. We have employed muon spin spectroscopy to characterize various organic free radicals which reside as isolated guests in structure II clathrates. The radicals are formed by reaction of atomic muonium (Mu) with the guest molecules: furan and two isomeric dihydrofurans...
October 11, 2016: Journal of Physical Chemistry. A
Pasquina Marzola, Federico Boschi, Francesco Moneta, Andrea Sbarbati, Carlo Zancanaro
Localization, differentiation, and quantitative assessment of fat tissues have always collected the interest of researchers. Nowadays, these topics are even more relevant as obesity (the excess of fat tissue) is considered a real pathology requiring in some cases pharmacological and surgical approaches. Several weight loss medications, acting either on the metabolism or on the central nervous system, are currently under preclinical or clinical investigation. Animal models of obesity have been developed and are widely used in pharmaceutical research...
2016: Frontiers in Pharmacology
Didem C Dogan, Seonghun Cho, Sun-Mi Hwang, Young-Min Kim, Hwanuk Guim, Tae-Hyun Yang, Seok-Hee Park, Gu-Gon Park, Sung-Dae Yim
Supportless Pt catalysts have several advantages over conventional carbon-supported Pt catalysts in that they are not susceptible to carbon corrosion. However, the need for high Pt loadings in membrane electrode assemblies (MEAs) to achieve state-of-the-art fuel cell performance has limited their application in proton exchange membrane fuel cells. Herein, we report a new approach to the design of a supportless Pt catalyst in terms of catalyst layer architecture, which is crucial for fuel cell performance as it affects water management and oxygen transport in the catalyst layers...
October 10, 2016: ACS Applied Materials & Interfaces
D Egorov, L Schwob, M Lalande, R Hoekstra, T Schlathölter
Multiply protonated peptides and proteins in the gas phase can respond to near edge X-ray absorption in three different ways: (i) non dissociative ionization and ionization accompanied by loss of small neutrals, both known to dominate for proteins with masses in the 10 kDa range. (ii) Formation of immonium ions, dominating for peptides in the 1 kDa range. (iii) Backbone scission leading to sequence ions which is typically weaker and has mainly been observed for peptides in the 1 kDa range. We have studied carbon 1s photoexcitation and photoionization for a series of peptides and proteins with masses covering the range from 0...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Martina Blunder, Andreas Orthaber, Rudolf Bauer, Franz Bucar, Olaf Kunert
We present a standardized, straightforward and efficient approach applicable in routine analysis of flavonoids combining sensitive NMR and HPLC experiments. The determination of the relative configuration of sugar moieties usually requires the acquisition of (13)C NMR shift values. We use a combination of HPLC and sensitive NMR experiments (1D-proton, 2D-HSQC) for the unique identification of known flavones, flavanones, flavonols and their glycosides. Owing to their broad range of polarity, we developed HPLC and UHPLC methods (H2O/MeOH/MeCN/HCOOH) which we applied and validated by analyzing 46 common flavones and flavanones and exemplified for four plant extracts...
March 1, 2017: Food Chemistry
Sergio Fombona, Maialen Espinal-Viguri, Miguel A Huertos, Jesús Díaz, Ramón López, M Isabel Menéndez, Julio Pérez, Lucía Riera
4,4'-Disubstituted-2,2'-bipyridine ligands coordinated to Mo(II) and Re(I) cationic fragments become dearomatized by an intramolecular nucleophilic attack from a deprotonated N-alkylimidazole ligand in cis disposition. The subsequent protonation of these neutral complexes takes place on a pyridine carbon atom rather than at nitrogen, weakening an aromatic C-C bond and affording a dihydropyridyl moiety. Computational calculations allowed for the rationalization of the formation of the experimentally obtained products over other plausible alternatives...
September 26, 2016: Chemistry: a European Journal
Lars H Finger, Jannick Guschlbauer, Klaus Harms, Jörg Sundermeyer
Depending on the amount of methanol present in solution, CO2 adducts of N-heterocyclic carbenes (NHCs) and N-heterocyclic olefins (NHOs) have been found to be in fully reversible equilibrium with the corresponding methyl carbonate salts [EMIm][OCO2 Me] and [EMMIm][OCO2 Me]. The reactivity pattern of representative 1-ethyl-3-methyl-NHO-CO2 adduct 4 has been investigated and compared with the corresponding NHC-CO2 zwitterion: The protonation of 4 with HX led to the imidazolium salts [NHO-CO2 H][X], which underwent decarboxylation to [EMMIm][X] in the presence of nucleophilic catalysts...
September 22, 2016: Chemistry: a European Journal
Serdar Elhatisari, Ning Li, Alexander Rokash, Jose Manuel Alarcón, Dechuan Du, Nico Klein, Bing-Nan Lu, Ulf-G Meißner, Evgeny Epelbaum, Hermann Krebs, Timo A Lähde, Dean Lee, Gautam Rupak
How do protons and neutrons bind to form nuclei? This is the central question of ab initio nuclear structure theory. While the answer may seem as simple as the fact that nuclear forces are attractive, the full story is more complex and interesting. In this work we present numerical evidence from ab initio lattice simulations showing that nature is near a quantum phase transition, a zero-temperature transition driven by quantum fluctuations. Using lattice effective field theory, we perform Monte Carlo simulations for systems with up to twenty nucleons...
September 23, 2016: Physical Review Letters
Mei Yang, Yijiang Liu, Hongbiao Chen, Duanguang Yang, Huaming Li
Metal-free N-doped carbon (NC) materials have been regarded as one of the most promising catalysts for the oxygen reduction reaction (ORR) in alkaline media because of their outstanding ORR catalytic activity, high stability, and good methanol tolerance. Up to now, only a small minority of such catalysts have been synthesized from triazine-based polymeric networks. Herein, we report the synthesis of such NC catalyst by directly pyrolyzing a nitrogen-rich, triazine-based polypyrrole network (TPN). The TPN is fabricated by oxidative polymerization of 2,4,6-tripyrrol-1,3,5-triazine monomer using TfOH as the protonating agent and benzoyl peroxide as the oxidizing agent...
October 7, 2016: ACS Applied Materials & Interfaces
Debabrata Pramanik, Prabal K Maiti
Various unique physical, chemical, mechanical and electronic properties of carbon nanotubes (CNTs) make them very useful materials for diverse potential application in many fields. Experimentally synthesized CNTs are generally found in bundle geometry with a mixture of different chiralities and present a unique challenge to separate them. In this paper we have proposed the PAMAM dendrimer to be an ideal candidate for this separation. To estimate the efficiency of the dendrimer for the dispersion of CNTs from the bundle geometry, we have calculated potential of mean forces (PMF)...
September 26, 2016: Soft Matter
Kaitlin G Henry, Lachlan M Blair, Jonathan Sperry, Elizabeth A Colby Davie
The dimeric natural product montamine was originally reported as two N-feruloylserotonin (moschamine) units linked by a nitrogen-nitrogen bond, but our recent synthesis of this symmetrical diacyl hydrazide structure revealed this to be incorrect. We subsequently hypothesized that the moschamine subunits were linked through the indole C4 site and that montamine was structurally identical to 4,4'-bismoschamine, a known natural product present in safflower oil. However, given that authentic samples of both montamine and 4,4'-bismoschamine were unavailable and that the NMR data for the natural products were recorded in different solvents, we were unable to unequivocally prove this hypothesis...
September 21, 2016: Organic & Biomolecular Chemistry
Qiang Zhang, Xingxing He, Ailing Han, Qingxia Tu, Guozhen Fang, Jifeng Liu, Shuo Wang, Haibo Li
An artificial enzyme was constructed by attaching short peptides with active sites (SHELKLKLKL, WLKLKLKL) onto carbon nanotubes (CNT). It was found that the combination of SHE amino acids was essential to form a catalytic triad. W was also incorporated into this artificial enzyme and acted as a substrate binding site, thus producing an enzyme model with synergism of 67.7% catalytic groups and 32.3% binding groups, CNT-(SHE/W)2:1-LKLKLKL. When the peptide SHELKLKLKL was attached with the catalytic triad site close to the surface of CNT, the composite had higher activity than a leucine-attached system terminated with the catalytic triad site, suggesting that CNT not only served as a platform for attaching active amino acids, but also created a hydrophobic microenvironment and facilitated the proton transfer process to enhance the catalytic activity...
September 29, 2016: Nanoscale
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