jablonkagroup/rise_ai_scientists huggingface dataset:
Authors: Zhao Wu | Summer D. Laffoon | Kami L. Hull
Source: Nature Communications (article, 2018-03-22)
Field: Chemistry — Inorganic Chemistry

Asymmetric synthesis of γ-branched amines via rhodium-catalyzed reductive amination Amines bearing γ-stereocenters are highly important structural motifs in many biologically active compounds. However, reported enantioselective syntheses of these molecules are indirect and often require multiple steps. Herein, we report a general asymmetric route for the one-pot synthesis of chiral γ-branched amines through the highly enantioselective isomerization of allylamines, followed by enamine exchange and subsequent chemoselective reduction. This protocol is suitable for establishing various tertiary stereocenters, including those containing dialkyl, diaryl, cyclic, trifluoromethyl, difluoromethyl, and silyl substituents, which allows for a rapid and modular synthesis of many chiral γ-branched amines. To demonstrate the synthetic utility, Terikalant and Tolterodine are synthesized using this method with high levels of enantioselectivity. Stereocenter ; Enantioselective synthesis ; Reductive amination ; Chemistry ; Amination ; Combinatorial chemistry ; Rhodium ; Trifluoromethyl ; Catalysis ; Organocatalysis ; Enamine ; Stereochemistry ; Organic chemistry Asymmetric Hydrogenation and Catalysis ; Chemical Synthesis and Analysis ; Synthetic Organic Chemistry Methods
Authors: Connie R. Jiménez | Hui Zhang | Christopher R. Kinsinger | Edouard C. Nice
Source: Clinical Proteomics (article, 2018-01-25)
Field: Chemistry — Spectroscopy

The cancer proteomic landscape and the HUPO Cancer Proteome Project The Human Cancer Proteome Project (Cancer-HPP) is an international initiative organized by HUPO whose key objective is to decipher the human cancer proteome through a coordinated effort by cancer proteome researchers around the world. The ultimate goal is to map the entire human cancer proteome to disclose tumor biology and drive improved diagnostics, treatment and management of cancer. Here we report the progress in the cancer proteomics field to date, and discuss future proteomic developments that will be needed to optimally delineate cancer phenotypes and advance the molecular characterization of this significant disease that is one of the leading causes of death worldwide. Proteome ; Human proteome project ; Cancer ; Proteomics ; Cancer biomarkers ; Computational biology ; DECIPHER ; Bioinformatics ; Biology ; Genetics Advanced Proteomics Techniques and Applications ; RNA modifications and cancer ; Cancer, Lipids, and Metabolism
Authors: Ravi Kumar | Azaj Ansari | Gopalan Rajaraman
Source: Chemistry - A European Journal (article, 2018-03-05)
Field: Chemistry — Inorganic Chemistry

Axial vs. Equatorial Ligand Rivalry in Controlling the Reactivity of Iron(IV)‐Oxo Species: Single‐State vs. Two‐State Reactivity High-valent iron-oxo species are known for their very high reactivity, and this aspect has been studied in detail over the years. The role of axial ligands in fine-tuning the reactivity of the iron(IV)-oxo species has been particularly well studied. The corresponding role of equatorial ligands, however, has rarely been explored, and is of prime importance in the development of non-heme chemistry. Here, we have undertaken detailed DFT calculations on [(L<sup>NHC</sup> )Fe<sup>IV</sup> (O)(CH<sub>3</sub> CN)]<sup>2+</sup> (1; L<sup>NHC</sup> =3,9,14,20-tetraaza1,6,12,17-tetraazoniapenta-cyclohexacosane-1(23),4,6(26),10,12(25),15,17(24),21-octaene) in comparison to compound II of cytochrome P450 [(porphyrin)Fe<sup>IV</sup> (O)(SH)]<sup>-</sup> (2) to probe this aspect. The electronic structures of 1 and 2 are found to vary significantly, implying a large variation in their reactivities. In particular, the strong equatorial ligand present in 1 significantly destabilizes the quintet states as compared to species 2. To fully understand the reactivity pattern of these species, we have modelled the hydroxylation of methane by both 1 and 2. Our calculations reveal that 1 reacts via a low-lying S=1 π pathway, and that the generally available S=2 σ pathway is not energetically accessible. In addition to having a significant barrier for C-H bond activation, the -OH rebound step is also computed to have a large barrier height, leading to a marked difference in reactivity between these two species. Of particular relevance here is the observation of pure triplet-state reactivity for 1. We have also attempted to test the role of axial ligands in fine-tuning the reactivity of 1, and our results demonstrate that, in contrast to heme systems, the axial ligands in 1 do not significantly influence the reactivity. This highlights the importance of designing equatorial ligands to fine-tune reactivity of high-valent iron(IV)-oxo species. Reactivity (psychology) ; Chemistry ; Ligand (biochemistry) ; Porphyrin ; Hydroxylation ; Stereochemistry ; Crystallography ; Photochemistry ; Receptor ; Organic chemistry ; Enzyme Metal-Catalyzed Oxygenation Mechanisms ; Porphyrin and Phthalocyanine Chemistry ; CO2 Reduction Techniques and Catalysts
Authors: Arnab Dawn | Marzieh Mirzamani | Christopher D. Jones | Dmitry S. Yufit | Shuo Qian | Jonathan W. Steed | Harshita Kumari
Source: Soft Matter (article, 2018-01-01)
Field: Materials Science — Biomaterials

Investigating the effect of supramolecular gel phase crystallization on gel nucleation Supramolecular gel phase crystallization offers a new strategy for drug polymorph screening and discovery. In this method, the crystallization outcome depends on the interaction between solute and gel fibre. While supramolecular gels have shown success in producing new polymorphs and crystals with novel morphologies, role of the gel and nature of gel-solute interaction remains largely unexplored. The present study aims to provide a comprehensive picture of the structural evolution of a supramolecular gel produced from a bis(urea) based gelator (G) in the presence of a polymorphic drug carbamazepine (CBZ). The structural aspects of the gel have been assessed by single crystal X-ray analysis, X-ray powder diffraction (XRPD) and solid state NMR spectroscopy. Small Angle Neutron Scattering (SANS) has been used to follow the changes in gel structure in the presence of CBZ. Visual evidence from morphological study and structural evolution observed at a macroscopic level from rheological measurements, shows good agreement with the SANS results. The concentration of the gelator and the relative proportion of G to CBZ were found to be crucial factors in determining the competitive nucleation events involving gelation and crystallization. At a critical G to CBZ ratio the effect of CBZ on gel structure was maximum and fiber bundling in the gel was found to be critically affected. This study offers important information about how the interplay of gelator assembly and gel-solute interactions can fine-tune the nucleation events in a supramolecular gel phase crystallization. Crystallization ; Nucleation ; Phase (matter) ; Supramolecular chemistry ; Chemical engineering ; Materials science ; Crystallography ; Chemistry ; Organic chemistry ; Crystal structure Supramolecular Self-Assembly in Materials ; Biochemical effects in animals ; Seaweed-derived Bioactive Compounds
Authors: Simon Millan | Gamall Makhloufi | Christoph Janiak
Source: Crystals (article, 2018-01-12)
Field: Chemistry — Inorganic Chemistry

Incorporating the Thiazolo[5,4-d]thiazole Unit into a Coordination Polymer with Interdigitated Structure The linker 2,5-di(4-pyridyl)thiazolo[5,4-d]thiazole (Dptztz), whose synthesis and structure is described here, was utilized together with benzene-1,3-dicarboxylate (isophthalate, 1,3-BDC2−) for the preparation of the two-dimensional coordination network [Zn(1,3-BDC)Dptztz]·DMF (DMF = dimethylformamide) via a solvothermal reaction. Compound [Zn(1,3-BDC)Dptztz]·DMF belongs to the class of coordination polymers with interdigitated structure (CIDs). The incorporated DMF solvent molecules can be removed through solvent exchange and evacuation such that the supramolecular 3D packing of the 2D networks retains porosity for CO2 adsorption in activated [Zn(1,3-BDC)Dptztz]. The first sorption study of a tztz-functionalized porous metal-organic framework material yields a BET surface of 417 m2/g calculated from the CO2 adsorption data. The heat of adsorption for CO2 exhibits a relative maximum with 27.7 kJ/mol at an adsorbed CO2 amount of about 4 cm3/g STP, which is interpreted as a gate-opening effect. Adsorption ; Metal-organic framework ; Thiazole ; Solvent ; Supramolecular chemistry ; Sorption ; Molecule ; Porosity ; Benzene ; Coordination polymer ; Polymer ; Polymer chemistry ; Dimethylformamide ; Linker ; Materials science ; Chemistry ; Crystallography ; Inorganic chemistry ; Physical chemistry ; Organic chemistry Metal-Organic Frameworks: Synthesis and Applications ; Covalent Organic Framework Applications ; Carbon dioxide utilization in catalysis
Authors: Florica Adriana Jerca | Valentin Victor Jerca | Richard Hoogenboom
Source: Journal of Polymer Science Part A Polymer Chemistry (article, 2018-10-03)
Field: Chemistry — Organic Chemistry

Well‐Defined Thermoresponsive Polymethacrylamide Copolymers with Ester Pendent Groups through One‐Pot Statistical Postpolymerization Modification of Poly(2‐Isopropenyl‐2‐Oxazoline) with Multiple Carboxylic Acids ABSTRACT Thermoresponsive polymers that undergo a solubility phase transition in water are important as basis for the development for a wide variety of responsive and smart materials. In this study, the synthesis of thermoresponsive copolymers is demonstrated by the straightforward one‐pot statistical postpolymerization modification of well‐defined poly(2‐isopropenyl‐2‐oxazoline) (PiPOx) by ring‐opening reaction with multiple carboxylic acids. The reactions are carried out using dual, triple, and quadruple mixtures of up to four different aliphatic carboxylic acids. The cloud point temperatures of the resulting polymethacrylamide copolymers with ester pendent groups can be finely tuned by adjusting the feed ratio and the hydrophilic–hydrophobic balance of the acids that are used for the ring‐opening modification of PiPOx. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57 , 360–366 Copolymer ; Oxazoline ; Polymer chemistry ; Cloud point ; Solubility ; Polymer ; Chemistry ; Thermoresponsive polymers in chromatography ; Lower critical solution temperature ; Carboxylic acid ; Materials science ; Organic chemistry ; Phase (matter) ; Aqueous solution ; Catalysis Advanced Polymer Synthesis and Characterization ; Synthesis and properties of polymers ; biodegradable polymer synthesis and properties
Authors: Agnieszka Adamus-Włodarczyk | Radosław A. Wach | Piotr Ulański | Janusz M. Rosiak | Marta Socka | Zois Tsinas | Mohamad Al‐Sheikhly
Source: Polymers (article, 2018-06-16)
Field: Materials Science — Biomaterials

On the Mechanisms of the Effects of Ionizing Radiation on Diblock and Random Copolymers of Poly(Lactic Acid) and Poly(Trimethylene Carbonate) This article demonstrates that ionizing radiation induces simultaneous crosslinking and scission in poly(trimethylene carbonate-<i>co</i>-d-lactide) diblock and random copolymers. Copolymer films were electron-beam (EB) irradiated up to 300 kGy under anaerobic conditions and subsequently examined by evaluation of their structure (FT-IR, NMR), molecular weight, intrinsic viscosities, and thermal properties. Radiation chemistry of the copolymers is strongly influenced by the content of ester linkages of the lactide component. At low lactide content, crosslinking reaction is the dominant one; however, as the lactide ratio increases, the ester linkages scission becomes more competent and exceeds the crosslinking. Electron paramagnetic resonance (EPR) measurements indicate that higher content of amorphous carbonate units in copolymers leads to a reduction in free radical yield and faster radical decay as compared to lactide-rich compositions. The domination of scission of ester bonds was confirmed by identifying the radiolytically produced alkoxyl and acetyl radicals, the latter being more stable due to its conjugated structure. Trimethylene carbonate ; Copolymer ; Electron paramagnetic resonance ; Lactide ; Amorphous solid ; Bond cleavage ; Materials science ; Polymer chemistry ; Carbonate ; Radical ; Photochemistry ; Polymer ; Chemistry ; Organic chemistry ; Catalysis ; Nuclear magnetic resonance ; Composite material biodegradable polymer synthesis and properties ; Polymer crystallization and properties ; Carbon dioxide utilization in catalysis
Authors: Gustavo Portalone | Kari Rissanen
Source: Crystal Growth & Design (article, 2018-09-04)
Field: Chemistry — Physical and Theoretical Chemistry

Multifacial Recognition in Binary and Ternary Cocrystals from 5-Halouracil and Aminoazine Derivatives A systematic analysis using single crystal X-ray diffraction was performed to explore the role exerted by potential intercomponent proton-transfer reactions in the supramolecular structures of A–B cocrystals formed by 5-haloderivatives of uracil (A), coupled with 2-aminoadenine simulants (aminoazines, B). Twelve new heterodimers were synthesized in different stoichiometries and cocrystallized by solvent cogrinding followed by solution crystallization. In the binary cocrystals, uracil or 1-methyluracil with halide modification at the 5 position (F, Cl, Br, I) was coupled with amino-aromatic N-heterocycles (melamine, 2,4,6-triaminopyrimidine, 2,6-diaminopyridine) as a multivalent site for pyrimidine nucleobase recognition. The crystallographic analysis showed that, next to the expected neutral three-point hydrogen bonds (TPI), ionized TPI, favored by A → B proton transfer, can be used for WC multifacial recognition. Noteworthy, the formation of the charged TPI, which depends on the acid/base properties of the components, always takes place between the more acidic site of the 5-halonucleobases (N3 atom) and the more basic site (imino N atom) of 2,4,6-triaminopyrimidine or 2,6-diaminopyridine, and melamine recognition unit results in being insufficiently basic to accept a proton. The general ability of pyrimidine nucleobases to provide electron donating groups to halogen bonding has been confirmed in seven cocrystals containing the 5-chloro, 5-bromo, or 5-iododerivatives coupled with melamine or 2,4,6-triaminopyrimidine. Considerations of the relative acidities of coformers A and of the relative basicities of coformers B allowed us to design and characterize by single-crystal X-ray diffraction the first ternary pyrimidine nucleobase-containing cocrystal based on the JANUS-WEDGE concept: the nucleobase–Janus–nucleobase (1:1:1) triad showing a 2,4,6-triamino pyrimidine molecule wedged via neutral and ionized TPI between the 5-fluorouracil/1-methyluracil pair in reverse WC fashion. Cocrystal ; Chemistry ; Melamine ; Nucleobase ; Uracil ; Hydrogen bond ; Crystallography ; Supramolecular chemistry ; Crystal engineering ; Pyrimidine ; Ternary operation ; Crystal structure ; Stereochemistry ; Molecule ; Organic chemistry ; DNA Crystallography and molecular interactions ; Crystal structures of chemical compounds ; Molecular Sensors and Ion Detection
Authors: Haoran Yang | Eric Wong | Tianshuo Zhao | Jennifer D. Lee | Huolin L. Xin | Miaofang Chi | Blaise Fleury | Hanyu Tang | E. Ashley Gaulding | Cherie R. Kagan | Christopher B. Murray
Source: ACS Nano (article, 2018-08-27)
Field: Materials Science — Materials Chemistry

Charge Transport Modulation in PbSe Nanocrystal Solids by Au<sub><i>x</i></sub>Ag<sub>1–<i>x</i></sub> Nanoparticle Doping Nanocrystal (NC) solids are an exciting class of materials, whose physical properties are tunable by choice of the NCs as well as the strength of the interparticle coupling. One can consider these NCs as "artificial atoms" in analogy to the formation of condensed matter from atoms. Akin to atomic doping, the doping of a semiconducting NC solid with impurity NCs can drastically alter its electronic properties. A high degree of complexity is possible in these artificial structures by adjusting the size, shape, and composition of the building blocks, which enables "designer" materials with targeted properties. Here, we present the doping of the PbSe NC solids with a series of Au <sub>x</sub>Ag<sub>1- x</sub> alloy nanoparticles (NPs). A combination of temperature-dependent electrical conductance and Seebeck coefficient measurements and room-temperature Hall effect measurements demonstrates that the incorporation of metal NPs both modifies the charge carrier density of the NC solids and introduces energy barriers for charge transport. These studies point to charge carrier injection from the metal NPs into the PbSe NC matrix. The charge carrier density and charge transport dynamics in the doped NC solids are adjustable in a wide range by employing the Au <sub>x</sub>Ag<sub>1- x</sub> NP with different Au:Ag ratio as dopants. This doping strategy could be of great interest for thermoelectric applications taking advantage of the energy filtering effect introduced by the metal NPs. Materials science ; Doping ; Thermoelectric effect ; Dopant ; Nanocrystal ; Nanoparticle ; Charge carrier ; Seebeck coefficient ; Chemical physics ; Nanotechnology ; Electron mobility ; Impurity ; Condensed matter physics ; Optoelectronics ; Thermal conductivity ; Chemistry ; Thermodynamics Quantum Dots Synthesis And Properties ; Chalcogenide Semiconductor Thin Films ; Advanced Thermoelectric Materials and Devices
Authors: Mohammad Aref Khalily | Hakan Usta | Mehmet Özdemir | Gökhan Bakan | F. Begum Dikecoglu | Charlotte J. C. Edwards‐Gayle | Jessica Hutchinson | Ian W. Hamley | Aykutlu Dâna | Mustafa O. Güler
Source: Nanoscale (article, 2018-01-01)
Field: Materials Science — Biomaterials

The design and fabrication of supramolecular semiconductor nanowires formed by benzothienobenzothiophene (BTBT)-conjugated peptides π-Conjugated small molecules based on a [1]benzothieno[3,2-b]benzothiophene (BTBT) unit are of great research interest in the development of solution-processable semiconducting materials owing to their excellent charge-transport characteristics. However, the BTBT π-core has yet to be demonstrated in the form of electro-active one-dimensional (1D) nanowires that are self-assembled in aqueous media for potential use in bioelectronics and tissue engineering. Here we report the design, synthesis, and self-assembly of benzothienobenzothiophene (BTBT)-peptide conjugates, the BTBT-peptide (BTBT-C3-COHN-Ahx-VVAGKK-Am) and the C8-BTBT-peptide (C8-BTBT-C3-COHN-Ahx-VVAGKK-Am), as β-sheet forming amphiphilic molecules, which self-assemble into highly uniform nanofibers in water with diameters of 11-13(±1) nm and micron-size lengths. Spectroscopic characterization studies demonstrate the J-type π-π interactions among the BTBT molecules within the hydrophobic core of the self-assembled nanofibers yielding an electrical conductivity as high as 6.0 × 10-6 S cm-1. The BTBT π-core is demonstrated, for the first time, in the formation of self-assembled peptide 1D nanostructures in aqueous media for potential use in tissue engineering, bioelectronics and (opto)electronics. The conductivity achieved here is one of the highest reported to date in a non-doped state. Bioelectronics ; Benzothiophene ; Conjugated system ; Nanowire ; Materials science ; Supramolecular chemistry ; Nanotechnology ; Fabrication ; Nanostructure ; Semiconductor nanostructures ; Molecular engineering ; Semiconductor ; Molecule ; Optoelectronics ; Chemistry ; Polymer ; Biosensor ; Organic chemistry Supramolecular Self-Assembly in Materials ; Advanced biosensing and bioanalysis techniques ; 2D Materials and Applications
Authors: Caleb R. Schlachter | Leily Daneshian | José A. Amaya | V. Klapper | Nicky Wybouw | Tomasz Borowski | Thomas Van Leeuwen | Vojislava Grbić | Miodrag Grbić | Thomas M. Makris | M. Chruszcz
Source: Insect Biochemistry and Molecular Biology (article, 2018-12-05)
Field: Chemistry — Inorganic Chemistry

Structural and functional characterization of an intradiol ring-cleavage dioxygenase from the polyphagous spider mite herbivore Tetranychus urticae Koch Tetranychus urticae ; Spider mite ; Dioxygenase ; Biology ; Active site ; Biochemistry ; Enzyme ; Stereochemistry ; Botany ; Chemistry ; Mite Metal-Catalyzed Oxygenation Mechanisms ; Insect symbiosis and bacterial influences ; Electrocatalysts for Energy Conversion
Authors: Morten H. Christensen | Peter P. Orth | Brian M. Andersen | Rafael M. Fernandes
Source: Physical Review Letters (article, 2018-07-30)
Field: Materials Science — Electronic, Optical and Magnetic Materials

Emergent Magnetic Degeneracy in Iron Pnictides due to the Interplay between Spin-Orbit Coupling and Quantum Fluctuations Recent experiments in iron pnictide superconductors reveal that, as the putative magnetic quantum critical point is approached, different types of magnetic order coexist over a narrow region of the phase diagram. Although these magnetic configurations share the same wave vectors, they break distinct symmetries of the lattice. Importantly, the highest superconducting transition temperature takes place close to this proliferation of near-degenerate magnetic states. In this Letter, we employ a renormalization group calculation to show that such a behavior naturally arises due to the effects of spin-orbit coupling on the quantum magnetic fluctuations. Formally, the enhanced magnetic degeneracy near the quantum critical point is manifested as a stable Gaussian fixed point with a large basin of attraction. Implications of our findings to the superconductivity of the iron pnictides are also discussed. Physics ; Condensed matter physics ; Superconductivity ; Degenerate energy levels ; Spin–orbit interaction ; Quantum critical point ; Quantum fluctuation ; Quantum phase transition ; Quantum ; Quantum mechanics ; Quantum phases ; Phase transition Iron-based superconductors research ; Corporate Taxation and Avoidance
Authors: Yichuan Zhang | Sébastien Moins | Olivier Coulembier | David Seveno | J. De Coninck
Source: Journal of Colloid and Interface Science (article, 2018-10-26)
Field: Materials Science — Surfaces, Coatings and Films

Capillary rise of polydimethylsiloxane around a poly(ethylene terephthalate) fiber versus viscosity: Existence of a sharp transition in the dynamic wetting behavior Wetting ; Polydimethylsiloxane ; Viscosity ; Wetting transition ; Dissipation ; Capillary action ; Materials science ; Fiber ; Composite material ; Displacement (psychology) ; Capillary number ; Thermodynamics ; Physics Surface Modification and Superhydrophobicity ; Advanced Sensor and Energy Harvesting Materials ; Fluid Dynamics and Heat Transfer
Authors: Takumaru Kurihara | Shun Satake | Manabu Hatano | Kazuaki Ishihara | Tatsuhiko Yoshino | Shigeki Matsunaga
Source: Chemistry - An Asian Journal (article, 2018-04-12)
Field: Chemistry — Inorganic Chemistry

Synthesis of 1,1′‐Spirobiindane‐7,7′‐Disulfonic Acid and Disulfonimide: Application for Catalytic Asymmetric Aminalization 1,1'-Spirobiindane-7,7'-disulfonic acid (SPISA) and 1,1'-spirobiindane-7,7'-disulfonimide were synthesized from 1,1'-spirobiindane-7,7'-diol (SPINOL) in 4 steps using a Pd-catalyzed Newman-Kwart rearrangement as a key step. These new catalysts possessing a rigid spirocyclic backbone were evaluated in a catalytic asymmetric aminalization reaction, and SPISA/iPr<sub>2</sub> NEt exhibited high enantioselectivity, demonstrating the utility of SPISA as a chiral Brønsted acid catalyst. Catalysis ; Brønsted–Lowry acid–base theory ; Enantioselective synthesis ; Chemistry ; Diol ; Combinatorial chemistry ; Stereochemistry ; Medicinal chemistry ; Organic chemistry Asymmetric Hydrogenation and Catalysis ; Asymmetric Synthesis and Catalysis ; Synthesis and Catalytic Reactions