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Yang Li, Xionghan Feng, Zhexue Lu, Hui Yin, Fan Liu, Quanjun Xiang
As a new carbon-based material, carbon dots (C-dots) have got widely preference because of its excellent electronic transfer capability. In this work, a novel ternary layered C-dots/g-C3N4/TiO2 nanosheets (CGT) composite photocatalysts were prepared by impregnation precipitation methods. The optimal ternary CGT composite samples revealed high photocatalytic hydrogen evolution rate in triethanolamine aqueous solutions, which exceeded the rate of the optimal g-C3N4/TiO2 composite sample by a factor of 5 times...
December 5, 2017: Journal of Colloid and Interface Science
Ganesan Karthikeyan, Alessio Bonucci, Gilles Casano, Guillaume Gerbaud, Sébastien Abel, Virginie Thomé, Laurent Kodjabachian, Axel Magalon, Bruno Guigliarelli, Valérie Belle, Olivier Ouari, Elisabetta Mileo
Approaching proteins structural dynamics and protein-protein interactions in the cellular environment is a fundamental challenge. Due to its absolute sensitivity and to its selectivity to paramagnetic species, Site-Directed Spin Labeling (SDSL) combined with Electron Paramagnetic Resonance (EPR) has the potential to evolve into an efficient method to follow conformational changes in proteins directly inside cells. Until now, the use of nitroxyde-based spin labels for in-cell studies has represented a major hurdle because of their short persistence in the cellular context...
December 11, 2017: Angewandte Chemie
M Giulbudagian, S Hönzke, J Bergueiro, D Işık, F Schumacher, S Saeidpour, S B Lohan, M C Meinke, C Teutloff, M Schäfer-Korting, G Yealland, B Kleuser, S Hedtrich, M Calderón
Highly hydrophilic, responsive nanogels are attractive as potential systems for the topical delivery of bioactives encapsulated in their three-dimensional polymeric scaffold. Yet, these drug carrier systems suffer from drawbacks for efficient delivery of hydrophobic drugs. Addressing this, β-cyclodextrin (βCD) could be successfully introduced into the drug carrier systems by exploiting its unique affinity toward dexamethasone (DXM) as well as its role as topical penetration enhancer. The properties of βCD could be combined with those of thermoresponsive nanogels (tNGs) based on dendritic polyglycerol (dPG) as a crosslinker and linear thermoresponsive polyglycerol (tPG) inducing responsiveness to temperature changes...
December 11, 2017: Nanoscale
Peng Xu, T J Huffman, In Hae Kwak, Amlan Biswas, M M Qazilbash
We investigate the temperature dependence of infrared properties at nanometer length scales in La0.67Sr0.33MnO3 (LSMO) thin film with a thickness of 47 unit cells grown on SrTiO3 substrate. The infrared nano-imaging experiments were performed using a near-field optical microscope in conjunction with a variable temperature heating stage. The near-field infrared data is consistent with the bulk of the LSMO film undergoing the thermally-driven non-percolative second-order transition from a metallic, ferromagnetic phase to an insulating, paramagnetic phase...
December 11, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Kouichi Nakagawa, Satoko Minakawa, Daisuke Sawamura, Hideyuki Hara
Continuous wave electron paramagnetic resonance (CW EPR) and X-band (9 GHz) EPR imaging (EPRI) were used to nondestructively investigate the possible differentiation between malignant melanoma (MM) and nevus pigmentosus (NP) melanin radicals in paraffin-embedded specimens. The EPR spectra of both samples were analyzed using linewidth, spectral pattern, and X-band EPRI. The CW-EPR spectra of the MM showed an additional signal overlap. Eumelanin- and pheomelanin-related radicals were observed in the MM specimens...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
Jia-Liang Chen, Yu Zhao, Yan-Jun Gong, Bin-Bin Pan, Xiao Wang, Xun-Cheng Su
Organic synthesis of a ligand with high binding affinities for paramagnetic lanthanide ions is an effective way of generating paramagnetic effects on proteins. These paramagnetic effects manifested in high-resolution NMR spectroscopy are valuable dynamic and structural restraints of proteins and protein-ligand complexes. A paramagnetic tag generally contains a metal chelating moiety and a reactive group for protein modification. Herein we report two new DTPA-like tags, 4PS-PyDTTA and 4PS-6M-PyDTTA that can be site-specifically attached to a protein with a stable thioether bond...
December 9, 2017: Journal of Biomolecular NMR
Yoshitaka Ishii, Ayesha Wickramasinghe, Isamu Matsuda, Yuki Endo, Yuji Ishii, Yusuke Nishiyama, Takahiro Nemoto, Takayuki Kamihara
Proton-detected solid-state NMR (SSNMR) spectroscopy has attracted much attention due to its excellent sensitivity and effectiveness in the analysis of trace amounts of amyloid proteins and other important biological systems. In this perspective article, we present the recent sensitivity limit of 1H-detected SSNMR using "ultra-fast" magic-angle spinning (MAS) at a spinning rate (νR) of 80-100 kHz. It was demonstrated that the high sensitivity of 1H-detected SSNMR at νR of 100 kHz and fast recycling using the paramagnetic-assisted condensed data collection (PACC) approach permitted "super-fast" collection of 1H-detected 2D protein SSNMR...
November 28, 2017: Journal of Magnetic Resonance
Navid Bavi, Adam D Martinac, D Marien Cortes, Omid Bavi, Pietro Ridone, Takeshi Nomura, Adam P Hill, Boris Martinac, Eduardo Perozo
The large conductance mechanosensitive channel (MscL), acts as an osmoprotective emergency valve in bacteria by opening a large, water-filled pore in response to changes in membrane tension. In its closed configuration, the last 36 residues at the C-terminus form a bundle of five α-helices co-linear with the five-fold axis of symmetry. Here, we examined the structural dynamics of the C-terminus of EcMscL using site-directed spin labelling electron paramagnetic resonance (SDSL EPR) spectroscopy. These experiments were complemented with computational modelling including molecular dynamics (MD) simulations and finite element (FE) modelling...
December 8, 2017: Scientific Reports
Nino Hatter, Benjamin W Heinrich, Daniela Rolf, Katharina J Franke
The competition of the free-spin state of a paramagnetic impurity on a superconductor with its screened counterpart is characterized by the energy scale of Kondo screening compared to the superconducting pairing energy Δ. When the experimental temperature suppresses Kondo screening, but preserves superconductivity, i.e., when Δ/k B > T > T K (k B is Boltzmann's constant and T K the Kondo temperature), this description fails. Here, we explore this temperature range in a set of manganese phthalocyanine molecules decorated with ammonia on Pb(111)...
December 8, 2017: Nature Communications
Pinar Senay Özbay, Sonja Stieb, Cristina Rossi, Oliver Riesterer, Andreas Boss, Tobias Weiss, Felix Kuhn, Klaas Paul Pruessmann, Daniel Nanz
BACKGROUND AND PURPOSE: Quantitative susceptibility mapping has been previously used to differentiate lesions in patients with brain tumors. The aim of this work was to characterize the response of magnetic susceptibility differences in malignant brain tumors and surrounding edema to hyperoxic and hypercapnic respiratory challenges. METHODS: Images of malignant brain tumor patients (2 glioblastoma multiforme, 2 anaplastic astrocytoma, 1 brain metastasis) with clinical MRI exams (contrast-enhanced T1w) were acquired at 3T...
December 5, 2017: Magnetic Resonance Imaging
Mark B Masthay, Calley N Eads, Amber N Johnson, Robert G Keil, Philip Miller, Ross E Jones, Joe D Mashburn, Harry B Fannin
Increasing interest in the thermodynamics of small and/or isolated systems, in combination with recent observations of negative temperatures of atoms in ultracold optical lattices, has stimulated the need for estimating the conventional, canonical temperature Tcconv of systems in equilibrium with heat baths using eigenstate-specific temperatures (ESTs). Four distinct ESTs-continuous canonical, discrete canonical, continuous microcanonical, and discrete microcanonical-are accordingly derived for two-level paramagnetic spin lattices (PSLs) in external magnetic fields...
December 7, 2017: Journal of Chemical Physics
Ali Akbar, Muhammad Waleed Khalid, Muhammad Sabieh Anwar
Magnetic linear birefringence and dichroism are investigated for the paramagnetic terbium gallium garnet (TGG) single crystal in the temperature range 8-100 K. The reciprocal nature is confirmed for the linear birefringence. Furthermore a theoretical model is validated that describes the intermixing of linear and circular birefringence. The ellipticity and rotation of the polarization ellipse are investigated in the light of these measurements. These otherwise minuscule magnetically induced effects are amplified at cryogenic temperatures and are determined by a phase-sensitive technique based on the Fourier decomposition of detected signal intensities...
November 27, 2017: Optics Express
Benjamin A Frandsen, Keith M Taddei, Ming Yi, Alex Frano, Zurab Guguchia, Rong Yu, Qimiao Si, Daniel E Bugaris, Ryan Stadel, Raymond Osborn, Stephan Rosenkranz, Omar Chmaissem, Robert J Birgeneau
We report on temperature-dependent pair distribution function measurements of Sr_{1-x}Na_{x}Fe_{2}As_{2}, an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C_{4} phase. Quantitative refinements indicate that the instantaneous local structure in the C_{4} phase comprises fluctuating orthorhombic regions with a length scale of ∼2  nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase...
November 3, 2017: Physical Review Letters
Dmitry Lebedev, Yuliana Pineda-Galvan, Yuki Tokimaru, Alexey Fedorov, Nicolas Kaeffer, Christophe Copéret, Yulia Pushkar
Improvement of the oxygen evolution reaction (OER) is a challenging step towards the development of sustainable energy technologies. Enhancing the OER rate and efficiency relies on understanding the water oxidation mechanism, which entails the characterization of the reaction intermediates. Very active Ru-bda type (bda is 2,2'-bipyridine-6,6'-dicarboxylate) molecular OER catalysts are proposed to operate via a transient 7-coordinate RuV=O intermediate, which so far has never been detected due to its high reactivity...
December 8, 2017: Journal of the American Chemical Society
Linda Cerofolini, Tommaso Staderini, Stefano Giuntini, Enrico Ravera, Marco Fragai, Giacomo Parigi, Roberta Pierattelli, Claudio Luchinat
Paramagnetic NMR data can be profitably incorporated in structural refinement protocols of metalloproteins or metal-substituted proteins, mostly as distance or angle restraints. However, they could in principle provide much more information, because the magnetic susceptibility of a paramagnetic metal ion is largely determined by its coordination sphere. This information can in turn be used to evaluate changes occurring in the coordination sphere of the metal when ligands (e.g.: inhibitors) are bound to the protein...
December 7, 2017: Journal of Biological Inorganic Chemistry: JBIC
Patrick J Herbert, Utsab Mitra, Kenneth L Knappenberger
In this Letter, we describe variable-temperature variable-field magnetic circular photoluminescence (VTVH-MCPL) spectroscopy as a complementary technique to absorption-based magnetic circular dichroism. A paramagnetic model system, Au25(SC8H9)18, is chosen to demonstrate the information content that is obtained from VTVH-MCPL. Specifically, the methods and analyses for the determination of electronic Landé g-factors, zero-field energy splittings, and relative A-, B-, and C-term contributions to the MCPL response are detailed...
December 1, 2017: Optics Letters
Franz Hagn, Mahmoud L Nasr, Gerhard Wagner
Suitable membrane mimetics are crucial to the performance of structural and functional studies of membrane proteins. Phospholipid nanodiscs (formed when a membrane scaffold protein encircles a small portion of a lipid bilayer) have native-like membrane properties. These have been used for a variety of functional studies, but structural studies by high-resolution solution-state NMR spectroscopy of membrane proteins in commonly used nanodiscs of 10-nm diameter were limited by the high molecular weight of these particles, which caused unfavorably large NMR line widths...
January 2018: Nature Protocols
Alessandro Tocchio, Naside Gozde Durmus, Kaushik Sridhar, Vigneshwaran Mani, Bukre Coskun, Rami El Assal, Utkan Demirci
In nature, cells self-assemble at the microscale into complex functional configurations. This mechanism is increasingly exploited to assemble biofidelic biological systems in vitro. However, precise coding of 3D multicellular living materials is challenging due to their architectural complexity and spatiotemporal heterogeneity. Therefore, there is an unmet need for an effective assembly method with deterministic control on the biomanufacturing of functional living systems, which can be used to model physiological and pathological behavior...
December 7, 2017: Advanced Materials
J H Lee, J Ma, S E Hahn, H B Cao, M Lee, Tao Hong, H-J Lee, M S Yeom, S Okamoto, H D Zhou, M Matsuda, R S Fishman
Localized spins and itinerant electrons rarely coexist in geometrically-frustrated spinel lattices. They exhibit a complex interplay between localized spins and itinerant electrons. In this paper, we study the origin of the unusual spin structure of the spinel CoV2O4, which stands at the crossover from insulating to itinerant behavior using the first principle calculation and neutron diffraction measurement. In contrast to the expected paramagnetism, localized spins supported by enhanced exchange couplings are frustrated by the effects of delocalized electrons...
December 7, 2017: Scientific Reports
Wenchuan Lai, Yuehui Yuan, Xu Wang, Yang Liu, Yulong Li, Xiangyang Liu
The mechanism of nucleophilic substitution deserves more investigation to include more reaction systems such as two-dimensional (2D) materials. In this study, we used fluorinated graphene (FG) as a representative 2D material to reveal the in-depth mechanism of its defluorination and nucleophilic substitution reaction under attack of common nucleophiles to explore the chemistry of 2D materials and enrich the research on the nucleophilic substitution reaction. DFT calculations and electron paramagnetic resonance spectroscopy (EPR) demonstrated that defluorination of FG occurred via a radical mechanism after a single electron transfer (SET) reaction between the nucleophile and C-F bond, and a spin center was generated on the nanosheet and fluorine anion...
December 7, 2017: Physical Chemistry Chemical Physics: PCCP
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