jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Xiaoying Zhang | Qingya Shen | Zhen Lei | Qianyi Wang | Jimin Zheng | Zongchao Jia
Source: Scientific Reports (article, 2019-06-24)
Field: Materials Science — Materials Chemistry

Characterization of metal binding of bifunctional kinase/phosphatase AceK and implication in activity modulation Abstract A unique bifunctional enzyme, isocitrate dehydrogenase kinase/phosphatase (AceK) regulates isocitrate dehydrogenase (IDH) by phosphorylation and dephosphorylation in response to nutrient availability. Herein we report the crystal structure of AceK in complex with ADP and Mn 2+ ions. Although the overall structure is similar to the previously reported structures which contain only one Mg 2+ ion, surprisingly, two Mn 2+ ions are found in the catalytic center of the AceK-Mn 2+ structure. Our enzymatic assays demonstrate that AceK-Mn 2+ showed higher phosphatase activity than AceK-Mg 2+ , whereas the kinase activity was relatively unaffected. We created mutants of AceK for all metal-coordinating residues. The phosphatase activities of these mutants were significantly impaired, suggesting the pivotal role of the binuclear (M1-M2) core in AceK phosphatase catalysis. Moreover, we have studied the interactions of Mn 2+ and Mg 2+ with wild-type and mutant AceK and found that the number of metal ions bound to AceK is in full agreement with the crystal structures. Combined with the enzymatic results, we demonstrate that AceK exhibits phosphatase activity in the presence of two, but not one, Mn 2+ ions, similar to PPM phosphatases. Taken together, we suggest that metal ions help AceK to balance and fine tune its kinase and phosphatase activities. Phosphatase ; Dephosphorylation ; Isocitrate dehydrogenase ; Phosphofructokinase 2 ; Kinase ; Enzyme ; Chemistry ; Bifunctional ; Biochemistry ; Mutant ; Phosphorylation ; Biology ; Catalysis Enzyme Structure and Function ; Biochemical and Molecular Research ; Protein Structure and Dynamics
Authors: Yonhua Tzeng | Ying-Ren Chen | JiunChi Lai | Boyen Huang
Source: IEEE Transactions on Nanotechnology (article, 2019-11-26)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Silver Nanoparticles SERS Sensors Using Rapid Thermal CVD Nanoscale Graphene Islands as Templates Surface enhanced Raman scattering (SERS) sensors have been fabricated by rapid thermal chemical vapor deposition of high-density nanoscale discrete graphene islands on copper foils followed by electroless chemical plating of discrete, closely spaced, and irregularly shaped silver nanoparticles on the copper surface where it is not covered by graphene islands. By fine tuning of the size and distribution of graphene islands and adjusting the deposition time for silver nanoparticles, nanoscale gaps between silver particles are fabricated. SERS sensors exhibiting Raman scattering signal enhancement factors as high as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> in reference to a bare copper have been demonstrated. Raman scattering signal has been measured from as low as 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-16</sup> M of R6G molecules in water. This article reports effects and optimization process of size and distribution of graphene islands on desirable morphology of chemically plated silver nanoparticles. The density of nanoscale gaps of a few nanometers in distance between neighboring silver nanoparticles is optimized, resulting in the demonstration of SERS sensors with very low detection limits for R6G molecules. Graphene ; Nanotechnology ; Nanoscopic scale ; Materials science ; Template ; Nanoparticle ; Chemical vapor deposition ; Optoelectronics ; Thermal ; Nanolithography ; Nanofluidics ; Fabrication ; Physics Gold and Silver Nanoparticles Synthesis and Applications ; Graphene research and applications ; Nanowire Synthesis and Applications
Authors: M Hussein N Assadi
Source: Journal of Physics Condensed Matter (article, 2019-11-26)
Field: Materials Science — Materials Chemistry

Na site doping a pathway for enhanced thermoelectric performance in Na <sub> 1− <i>x</i> </sub> CoO <sub>2</sub> ; the case of Gd and Yb dopants Doping is considered to be the main method for improving the thermoelectric performance of layered sodium cobaltate (Na<sub>1-x</sub> CoO<sub>2</sub>). However, in the vast majority of past reports, the equilibrium location of the dopant in the Na<sub>1-x</sub> CoO<sub>2</sub>' complex layered lattice has not been confidently identified. Consequently, a universal strategy for choosing a suitable dopant for enhancing Na<sub>1-x</sub> CoO<sub>2</sub>'s figure of merit is yet to be established. Here, by examining the formation energy of Gd and Yb dopants in Na<sub>0.75</sub>CoO<sub>2</sub> and Na<sub>0.50</sub>CoO<sub>2</sub>, we demonstrate that in an oxygen poor environment, Gd and Yb dopants reside in the Na layer while in an oxygen rich environment these dopants replace a Co in CoO<sub>2</sub> layer. When at Na layer, Gd and Yb dopants reduce the carrier concentration via electron-hole recombination, simultaneously increasing the Seebeck coefficient (S) and reducing electric conductivity (σ). Na site doping, however, improves the thermoelectric power factor (PF), only in Na<sub>0.50</sub>CoO<sub>2</sub>. When replacing a Co, these dopants reduce S and PF. The results demonstrate how thermoelectric performance critically depends on the synthesis environment that must be fine-tuned for achieving any thermoelectric enhancement. Dopant ; Thermoelectric effect ; Seebeck coefficient ; Doping ; Thermoelectric materials ; Electrical resistivity and conductivity Advanced Thermoelectric Materials and Devices ; Magnetic and transport properties of perovskites and related materials ; Copper-based nanomaterials and applications
Authors: David J. Clarke
Source: Chem (article, 2019-05-01)
Field: Chemistry — Spectroscopy

Protein Mass Spectrometry: Structural Characterization and Clinical Diagnosis Mass spectrometry ; Chemistry ; Electrospray ionization ; Ionization ; Desorption electrospray ionization ; Biomolecule ; Direct electron ionization liquid chromatography–mass spectrometry interface ; Capillary electrophoresis–mass spectrometry ; Protein mass spectrometry ; Matrix-assisted laser desorption electrospray ionization ; Ion source ; Chemical ionization ; Analytical Chemistry (journal) ; Electron ionization ; Chromatography ; Ion ; Organic chemistry Mass Spectrometry Techniques and Applications ; Advanced Proteomics Techniques and Applications ; Metabolomics and Mass Spectrometry Studies
Authors: Huifang Zhao | Chaofan Sun | Hang Yin | Yuanzuo Li | Jianbo Gao | Ying Shi | Mengtao Sun
Source: Scientific Reports (article, 2019-05-23)
Field: Materials Science — Materials Chemistry

Tunable electron transfer rate in a CdSe/ZnS-based complex with different anthraquinone chloride substitutes We use femtosecond transient absorption spectroscopy to study ultrafast electron transfer (ET) dynamics in a model donor and acceptor system using CdSe/ZnS core/shell structure quantum dots (QDs) as donors and anthraquinone (AQ) molecules as acceptors. The ET rate can be enhanced by decreasing the number of chlorine substituents in the AQ molecules because that increases the driving force, which is the energy level offset between the conduction band energy of CdSe/ZnS and the lowest upper molecular orbital potential of AQ derivatives, as confirmed by cyclic voltammetry measurements. However, the electronic coupling between the QDs and AQ derivatives, and the sum of reorganization energy of AQ molecules and solvent calculated by density functional theory are not the main reasons for the change in ET rate in three systems. Our findings provide new insights into selecting an acceptor molecule and will be useful in tuning ET processes for advanced QD-based applications. Ultrafast laser spectroscopy ; Acceptor ; Molecule ; Electron transfer ; Photochemistry ; Marcus theory ; Quantum dot ; Electron acceptor ; Femtosecond ; Density functional theory ; Chemistry ; Band gap ; Anthraquinone ; Materials science ; Spectroscopy ; Chemical physics ; Computational chemistry ; Nanotechnology ; Optoelectronics ; Reaction rate constant ; Physics Quantum Dots Synthesis And Properties ; Photochemistry and Electron Transfer Studies ; Molecular Junctions and Nanostructures
Authors: Nevena Vukić | Ivan Ristić | Milena Marinović‐Cincović | Radmila Radičević | Branka Pilić | Suzana Cakić | Jaroslava Budìnski‐Simendìć
Source: Hemijska industrija (article, 2019-01-01)
Field: Materials Science — Biomaterials

Influence of different functionalization methods of multi-walled carbon nanotubes on the properties of poly(L-lactide) based nanocomposites This paper presents influence of the type of carbon nanotube functionalization on properties of poly(L-lactide) (PLLA) based nanocomposite materials. For this purpose surface modifications of multi-walled carbon nanotubes (MWCNTs) were performed by chemical and irradiation techniques, while thermo gravimetric analysis, UV-Visible and Fourier-transform infrared (FT-IR) spectroscopies confirmed successful covalent functionalization. Series of PLLA bionanocom-posites with different contents of functionalized MWCNTs (0.7; 1.6; 2.1 wt%), were synthesized via ring-opening solution polymerisation of L-lactide. FT-IR analysis confirmed that grafting of L-lactide, under controlled condition, is possible to perform starting from the surface of functionalized MWCNTs. From differential scanning calorimetry results it was concluded that even low contents of chemically and irradiation functionalized MWCNTs had a significant effect on thermal properties of the prepared nanocomposites, raising the values of melting and glass transition temperatures. Thermogravimetric analysis (TGA) has shown that the degradation onset temperature for composites with chemically functionalized MWCNTs, was much higher than that for the neat poly(L-lactide) sample and composites with irradiation functionalized MWCNTs. Morphology studies by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that poly(L-lactide) covered surfaces and separated functionalized MWCNTs. Good dispersion of carbon nanotubes in polymer matrix enabled conductivity of synthesized materials, as determined by conductivity tests. Thermogravimetric analysis ; Materials science ; Surface modification ; Nanocomposite ; Carbon nanotube ; Differential scanning calorimetry ; Lactide ; Scanning electron microscope ; Chemical engineering ; Fourier transform infrared spectroscopy ; Polymer ; Composite material ; Polymer chemistry ; Polymerization biodegradable polymer synthesis and properties ; Polymer Nanocomposite Synthesis and Irradiation ; Carbon Nanotubes in Composites
Authors: Guillermo Moreno‐Alcántar | L. SALAZAR | Guillermo Romo-Islas | Marcos Flores‐Álamo | Hugo Torrens
Source: Molecules (article, 2019-12-03)
Field: Chemistry — Organic Chemistry

Exploring the Self-Assembled Tacticity in Aurophilic Polymeric Arrangements of Diphosphanegold(I) Fluorothiolates Despite the recurrence of aurophilic interactions in the solid-state structures of gold(I) compounds, its rational control, modulation, and application in the generation of functional supramolecular structures is an area that requires further development. The ligand effects over the aurophilic-based supramolecular structures need to be better understood. This paper presents the supramolecular structural diversity of a series of new 1,3-bis(diphenylphosphane)propane (dppp) gold(I) fluorinated thiolates with the general formula [Au<sub>2</sub>(SR<sub>F</sub>)<sub>2</sub>(μ-dppp)] (SR<sub>F</sub> = SC<sub>6</sub>F<sub>5</sub> (<b>1</b>); SC<sub>6</sub>HF<sub>4</sub>-4 (<b>2</b>); SC<sub>6</sub>H<sub>3</sub>(CF<sub>3</sub>)<sub>2</sub>-3,5 (<b>3</b>); SC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-2 (<b>4</b>); SC<sub>6</sub>H<sub>4</sub>CF<sub>3</sub>-4 (<b>5</b>); SC<sub>6</sub>H<sub>3</sub>F<sub>2</sub>-3,4 (<b>6</b>); SC<sub>6</sub>H<sub>3</sub>F<sub>2</sub>-3,5 (<b>7</b>); SC<sub>6</sub>H<sub>4</sub>F-2 (<b>8</b>); SC<sub>6</sub>H<sub>4</sub>F-3 (<b>9</b>); SC<sub>6</sub>H<sub>4</sub>F-4 (<b>10</b>)). These compounds were synthesized and characterized, and six of their solid-state crystalline structures were determined using single-crystal X-ray diffraction. In the crystalline arrangement, they form aurophilic-bridged polymers. In these systems, the changes in the fluorination patterns of the thiolate ligands tune the aurophilic-induced self-assembly of the compounds causing tacticity and chiral differentiation of the monomers. This is an example of the use of ligand effects on the tune of the supramolecular association of gold complexes. Supramolecular chemistry ; Monomer ; Tacticity ; Ligand (biochemistry) ; Solid-state ; Crystallography ; Chemistry ; Polymer ; Crystal structure ; Materials science ; Nanotechnology ; Organic chemistry ; Polymerization ; Receptor Organometallic Complex Synthesis and Catalysis ; Organometallic Compounds Synthesis and Characterization ; Metal complexes synthesis and properties
Authors: Malik Salman Haider | Michael M. Lübtow | Sebastian Endres | Vladimir Aseyev | Ann‐Christin Pöppler | Robert Luxenhofer
Source: ChemRxiv (preprint, 2019-08-23)
Field: Chemistry — Organic Chemistry

Think Beyond the Core: The Impact of the Hydrophilic Corona on the Drug Solubilization Using Polymer Micelles Polymeric micelles are typically characterized as core-shell structures. The hydrophobic inner core is considered as depot for hydrophobic molecules such as drugs or catalysts and the corona forming block acts as protective, stabilizing and solubilizing interface between the hydrophobic core and the external aqueous milieu. Tremendous efforts have been made to tune the hydrophobic block to increase the drug loading and stability of the micelles, while the role of hydrophilic blocks regarding drug loading and stability of micelles is rarely studied in detail. To do so, we investigated a small library of structurally similar A-B-A type amphiphiles based on poly(2-oxazoline)s and poly(2-oxazine)s by varying the hydrophilic block A utilizing poly(2-methyl-2-oxazoline) (A) or poly(2-ethyl-2-oxazoline) (A*), both excellently water-soluble polymers that are able to provide beneficial stealth properties. Surprisingly, major differences in loading capacities from A-B-A > A*-B-A > A*-B-A* highlight the impact of the hydrophilic corona of the polymer micelles on drug loading and stability. 1H-NMR spectroscopy revealed that the hydrophilic pEtOx exhibits a stronger interaction with the cargo compared with its more hydrophilic counterpart pMeOx, reducing colloidal stability of the drug loaded micelles at lower drug loading. To gain more insights, formulations were also characterized by diffusion ordered and nuclear Overhauser effect NMR spectroscopy, dynamic light scattering and (micro) differential scanning calorimetry. Our findings suggest that the interaction between the hydrophilic block and the guest molecule should be considered an important but previously largely ignored factor for the rational design of polymeric micelles. Micelle ; Polymer ; Amphiphile ; Dynamic light scattering ; Copolymer ; Chemical engineering ; Chemistry ; Polymer chemistry ; Materials science ; Aqueous solution ; Organic chemistry ; Nanoparticle ; Nanotechnology Surfactants and Colloidal Systems ; Nanoparticle-Based Drug Delivery ; Advanced Polymer Synthesis and Characterization
Authors: Marta Feroci | Tommaso Civitarese | Fabiana Pandolfi | Rita Petrucci | Daniele Rocco | Daniela Zane | Giuseppe Zollo | Leonardo Mattiello
Source: ChemElectroChem (article, 2019-07-29)
Field: Materials Science — Polymers and Plastics

Electrochemical Studies of New Donor‐Acceptor Oligothiophenes Abstract Electrochemical studies on a series of new conjugated oligothiophene derivatives are reported. The molecular architectures (D−A and A−D−A) of these compounds present different donor cores (thiophene, bithiophene) with different numbers of 3‐octylthiophene units (that act as π‐bridge and solubilizing components). The acceptor end groups adopted were, in all the cases, ethyl cyanoacrylate units. The results from voltammetric experiments confirm the close relationship between the structure of these oligothiophenes and their electrochemical behavior. Furthermore, we carried out quantum mechanical calculations to be able to obtain the HOMO/LUMO characteristics of some of our compounds in order to confirm our hypotheses on their electrochemical behavior. Moreover, the roles of the oligothiophene backbone and the ethyl cyanoacrylate group in cyclic voltammetry were elucidated by carrying out two different electrolyses at anodic and cathodic peak potentials. In particular, we were successful in the anodic dimerization of a tetrathiophene (D−A) to an octithiophene (A−D−A) (in high yield) with a considerable shortening of the chemical synthesis. Thiophene ; Electrochemistry ; Cyclic voltammetry ; Conjugated system ; Acceptor ; HOMO/LUMO ; Materials science ; Anode ; Chemistry ; Photochemistry ; Molecule ; Organic chemistry ; Polymer ; Physical chemistry ; Electrode Conducting polymers and applications ; Organic Electronics and Photovoltaics ; Electrochemical Analysis and Applications
Authors: Ana González | Víctor Garcés | Laura Sabio | Félix Velando | Miguel López‐Haro | Natividad Gálvez | José J. Calvino | José M. Domínguez‐Vera
Source: Journal of Applied Physics (article, 2019-08-01)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Optical and tomography studies of water-soluble gold nanoparticles on bacterial exopolysaccharides Gold nanoparticles of different shapes (spherical, rods, and prisms) aggregate when deposited onto Lactobacillus fermentum's exopolysaccharide (EPS), a set of polysaccharides excreted by the bacteria. Transmission electron microscopy studies revealed that gold nanoparticles have high affinity for EPS. UV-vis spectra of aggregated gold nanoparticles showed additional absorbance peaks at lower energies in comparison with isolated nanoparticles. In the case of gold nanoprisms, the aggregation leads to a new absorption at a very low energy centered at 1100 nm. Moreover, the EPS of L. fermentum itself produces gold aggregates from a Au(III) solution. Surface-enhanced Raman spectroscopy performances for the detection of rhodamine B of gold aggregates were drastically different. A tomography study on all samples revealed clear differences in the extension of the EPS coating on the gold nanoparticles. Only the gold aggregate in which gold interparticle surfaces were exposed to RhB showed a drastic increase (two orders of magnitude) of intensity in the Raman spectrum of RhB. Colloidal gold ; Nanoparticle ; Absorbance ; Raman spectroscopy ; Lactobacillus fermentum ; Materials science ; Surface-enhanced Raman spectroscopy ; Transmission electron microscopy ; Rhodamine B ; Chemistry ; Analytical Chemistry (journal) ; Nanotechnology ; Raman scattering ; Bacteria ; Chromatography ; Optics ; Lactobacillus plantarum ; Photocatalysis ; Organic chemistry Gold and Silver Nanoparticles Synthesis and Applications ; Biosensors and Analytical Detection ; Nanoparticles: synthesis and applications
Authors: Stéphane Mazerat | Joséphine Lacroix | R. Pailler
Source: Microporous and Mesoporous Materials (article, 2019-05-17)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Carbide derived carbon obtained from SiC-based fibers by phosphating-NaOH bath process Materials science ; Carbide ; Carbon fibers ; Chemical engineering ; Monolayer ; Fiber ; Composite material ; Phosphoric acid ; Dissolution ; Specific surface area ; Mesoporous material ; Nanotechnology ; Metallurgy ; Chemistry ; Organic chemistry ; Composite number Supercapacitor Materials and Fabrication ; Advanced ceramic materials synthesis ; Graphene research and applications
Authors: Tatsuya Ayabe | Bun Chan | Takamasa Sagara
Source: Journal of Electroanalytical Chemistry (article, 2019-11-22)
Field: Chemistry — Physical and Theoretical Chemistry

Fluorination effect on electrochemistry of dibutyl viologen in aqueous solution Chemistry ; Viologen ; Dication ; Aqueous solution ; Solvation ; Electrochemistry ; Electron transfer ; Radical ion ; Redox ; Inorganic chemistry ; Photochemistry ; Physical chemistry ; Ion ; Organic chemistry ; Electrode Photochemistry and Electron Transfer Studies ; Per- and polyfluoroalkyl substances research ; Electrochemical Analysis and Applications
Authors: Lubin Ni | Robin Güttinger | Carlos A. Triana | Bernhard Spingler | Kim K. Baldridge | Greta R. Patzke
Source: Dalton Transactions (article, 2019-01-01)
Field: Materials Science — Materials Chemistry

Pathways towards true catalysts: computational modelling and structural transformations of Zn-polyoxotungstates Current catalysis undergoes a paradigm shift from molecular and heterogeneous realms towards new dynamic catalyst concepts. This calls for innovative strategies to understand the essential catalytic motifs and true catalysts emerging from oxidative transformation processes. Polyoxometalate (POM) clusters offer an inexhaustible reservoir for new noble metal-free catalysts and excellent model systems whose structure-activity relationships and mechanisms remain to be explored. Here, we first introduce a new {Zn<sub>n</sub>Na<sub>6-n</sub>(B-α-SbW<sub>9</sub>O<sub>33</sub>)<sub>2</sub>} (n = 3-6) catalyst family with remarkable tuning options of the Zn-based core structure and high activity in H<sub>2</sub>O<sub>2</sub>-assisted catalytic alcohol oxidation as a representative reaction. Next, high level solution-based computational modelling of the intermediates and transition states was carried out for [Zn<sub>6</sub>Cl<sub>6</sub>(SbW<sub>9</sub>O<sub>33</sub>)<sub>2</sub>]<sup>12-</sup> as a representative well-defined case. The results indicate a radical-based oxidation process with the involvement of tungsten and adjacent zinc metal centers. The {Zn<sub>n</sub>Na<sub>6-n</sub>(B-α-SbW<sub>9</sub>O<sub>33</sub>)<sub>2</sub>} series indeed efficiently catalyses alcohol oxidation via peroxotungstate intermediates, in agreement with strong spectroscopic support and other experimental evidence for the radical mechanism. Finally, the high performance of [Zn<sub>6</sub>Cl<sub>6</sub>(SbW<sub>9</sub>O<sub>33</sub>)<sub>2</sub>]<sup>12-</sup> was traced back to its transformation into a highly active and robust disordered Zn/W-POM catalyst. The atomic short-range structure of this resting pre-catalyst was elucidated by RMC modelling of the experimental W-L<sub>3</sub> and Zn-K edge EXAFS spectra and supported with further analytical methods. We demonstrate that computational identification of the reactive sites combined with the analytical tracking of their dynamic transformations provides essential input to expedite cluster-based molecular catalyst design. Catalysis ; Chemistry ; Computational chemistry ; Organic chemistry Polyoxometalates: Synthesis and Applications ; Chemical Synthesis and Reactions ; Catalysis and Oxidation Reactions