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Physical Chemistry

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https://www.readbyqxmd.com/read/29656543/diastereoselective-synthesis-of-highly-substituted-amino-and-pyrrolidino-tetrahydrofurans-as-lead-like-molecular-scaffolds
#1
Christopher John Moody, Steven Wales, Elena Merisor, Holly Adcock, Christopher Pearce, Ian Strutt, William Lewis, Daniel Hamza
A series of highly substituted tetrahydrofurans (THFs), decorated with modifiable 2-aryl, 3-carboxy and 4-amino substituents, has been prepared for biological evaluation within the European Lead Factory. Diastereoselective reductive amination of pre-functionalised 4-oxofurans, readily prepared from cinnamate esters via oxa-Michael/Dieckmann annulation, provided the requisite THF cores on gram scale with three contiguous stereocentres, including full substitution at C-3. In a second series, a pyrrolidine ring was fused to the same oxofuran scaffold via an intramolecular reductive amination, inverting the configuration at C-4 relative to the other ring substituents...
April 14, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29656408/in-silico-tracking-of-individual-species-accelerating-progress-in-macromolecular-engineering-and-design
#2
Dagmar R D'hooge
The beneficial use of computer simulations to track the microstructural evolution of individual species is highlighted in view of macromolecular engineering and design, considering two case studies on catalytic polymerization, and both "low" (<100) and "high" (>100) chain lengths, that is, i) atom transfer radical copolymerization of n-butyl acrylate and styrene aiming at the synthesis of functional macrospecies of "identical' chain length; and ii) chain shuttling polymerization of ethylene and 1-octene toward the production of segmented block copolymers with "soft" and "hard" segments...
April 14, 2018: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/29655839/free-silanols-and-ionic-liquids-as-their-suppressors-in-liquid-chromatography
#3
REVIEW
Magdalena Buszewska-Forajta, Michał J Markuszewski, Roman Kaliszan
In this review, we will firstly discuss the types and the general properties of silica, focusing on the silica support used in chromatography and capillary electrophoresis. Additionally, the characterization of functional groups (silanols and siloxanes) will be considered in terms of activity of the stationary phases. We will then discuss physical chemistry of the stationary phases applied in liquid chromatography and capillary electrophoresis. The use of ionic liquids as a silanols' suppressors will be presented in the next parts of the study, along with the examples of specific applications...
April 7, 2018: Journal of Chromatography. A
https://www.readbyqxmd.com/read/29655337/five-and-six-electron-harmonium-atoms-highly-accurate-electronic-properties-and-their-application-to-benchmarking-of-approximate-1-matrix-functionals
#4
Jerzy Cioslowski, Krzysztof Strasburger
Electronic properties of several states of the five- and six-electron harmonium atoms are obtained from large-scale calculations employing explicitly correlated basis functions. The high accuracy of the computed energies (including their components), natural spinorbitals, and their occupation numbers makes them suitable for testing, calibration, and benchmarking of approximate formalisms of quantum chemistry and solid state physics. In the case of the five-electron species, the availability of the new data for a wide range of the confinement strengths ω allows for confirmation and generalization of the previously reached conclusions concerning the performance of the presently known approximations for the electron-electron repulsion energy in terms of the 1-matrix that are at heart of the density matrix functional theory (DMFT)...
April 14, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29652886/simulations-of-camera-based-single-molecule-fluorescence-experiments
#5
Richard Börner, Danny Kowerko, Mélodie C A S Hadzic, Sebastian L B König, Marc Ritter, Roland K O Sigel
Single-molecule microscopy has become a widely used technique in (bio)physics and (bio)chemistry. A popular implementation is single-molecule Förster Resonance Energy Transfer (smFRET), for which total internal reflection fluorescence microscopy is frequently combined with camera-based detection of surface-immobilized molecules. Camera-based smFRET experiments generate large and complex datasets and several methods for video processing and analysis have been reported. As these algorithms often address similar aspects in video analysis, there is a growing need for standardized comparison...
2018: PloS One
https://www.readbyqxmd.com/read/29650670/a-blueprint-for-demonstrating-quantum-supremacy-with-superconducting-qubits
#6
C Neill, P Roushan, K Kechedzhi, S Boixo, S V Isakov, V Smelyanskiy, A Megrant, B Chiaro, A Dunsworth, K Arya, R Barends, B Burkett, Y Chen, Z Chen, A Fowler, B Foxen, M Giustina, R Graff, E Jeffrey, T Huang, J Kelly, P Klimov, E Lucero, J Mutus, M Neeley, C Quintana, D Sank, A Vainsencher, J Wenner, T C White, H Neven, J M Martinis
A key step toward demonstrating a quantum system that can address difficult problems in physics and chemistry will be performing a computation beyond the capabilities of any classical computer, thus achieving so-called quantum supremacy. In this study, we used nine superconducting qubits to demonstrate a promising path toward quantum supremacy. By individually tuning the qubit parameters, we were able to generate thousands of distinct Hamiltonian evolutions and probe the output probabilities. The measured probabilities obey a universal distribution, consistent with uniformly sampling the full Hilbert space...
April 13, 2018: Science
https://www.readbyqxmd.com/read/29629774/polymer-valence-isomerism-poly-dewar-o-xylylene-s
#7
Rong Zhu, Timothy M Swager
Poly( o-xylylene) (POX) has long been a challenging synthetic target despite its simple structure and potentially useful physical properties. In this report, we demonstrate a valence isomer strategy that leads to the formation of high molecular weight POX via an intermediate polymer of a unique structure, namely poly(Dewar- o-xylylene) (PDOX). We show that the free radical polymerization of highly strained Dewar- o-xylylene (DOX) monomer afforded PDOX, a material with a high density of Dewar benzene units in the backbone through ring-retaining propagation...
April 9, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29626546/aptamer-chemistry
#8
Pascal Röthlisberger, Marcel Hollenstein
Aptamers are single-stranded DNA or RNA molecules capable of tightly binding to specific targets. These functional nucleic acids are obtained by an in vitro Darwinian evolution method coined SELEX (Systematic Evolution of Ligands by EXponential enrichment). Compared to their proteinaceous counterparts, aptamers offer a number of advantages including a low immunogenicity, a relative ease of large-scale synthesis at affordable costs with little or no batch-to-batch variation, physical stability, and facile chemical modification...
April 4, 2018: Advanced Drug Delivery Reviews
https://www.readbyqxmd.com/read/29622838/a-physical-inorganic-approach-for-the-elucidation-of-active-iron-species-and-mechanism-in-iron-catalyzed-cross-coupling
#9
Stephanie H Carpenter, Michael L Neidig
Detailed studies of iron speciation and mechanism in iron-catalyzed cross-coupling reactions are critical for providing the necessary fundamental insight to drive new reaction development. However, such insight is challenging to obtain due to the prevalence of mixtures of unstable, paramagnetic organoiron species that can form in this chemistry. A physical-inorganic research approach combining freeze-trapped inorganic spectroscopic studies, organometallic synthesis and GC/kinetic studies provides a powerful method for studying such systems...
December 2017: Israel Journal of Chemistry
https://www.readbyqxmd.com/read/29616689/kinetics-in-the-real-world-linking-molecules-processes-and-systems
#10
EDITORIAL
Katharina Kohse-Höinghaus, Jürgen Troe, Jens-Uwe Grabow, Matthias Olzmann, Gernot Friedrichs, Klaus-Dieter Hungenberg
Unravelling elementary steps, reaction pathways, and kinetic mechanisms is key to understanding the behaviour of many real-world chemical systems that span from the troposphere or even interstellar media to engines and process reactors. Recent work in chemical kinetics provides detailed information on the reactive changes occurring in chemical systems, often on the atomic or molecular scale. The optimisation of practical processes, for instance in combustion, catalysis, battery technology, polymerisation, and nanoparticle production, can profit from a sound knowledge of the underlying fundamental chemical kinetics...
April 4, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29614859/click-conjugation-of-cloaked-peptide-ligands-to-microbubbles
#11
Connor Slagle, Douglas H Thamm, Elissa K Randall, Mark Andrew Borden
Interest in the use of targeted microbubbles for ultrasound molecular imaging (USMI) has been growing in recent years as a safe and efficacious means of diagnosing tumor angiogenesis and assessing response to therapy. Of particular interest are cloaked microbubbles, which improve specificity by concealing the ligand from blood components until they reach the target vasculature, where the ligand can be transiently revealed for firm receptor-binding by ultrasound acoustic radiation force pulses. Herein, a bio-orthogonal "click" conjugation chemistry is introduced to decorate the surface of cloaked 4-5 μm diameter microbubbles as part of a sterile and reproducible production process...
April 4, 2018: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/29611563/liquid-metals-fundamentals-and-applications-in-chemistry
#12
REVIEW
T Daeneke, K Khoshmanesh, N Mahmood, I A de Castro, D Esrafilzadeh, S J Barrow, M D Dickey, K Kalantar-Zadeh
Post-transition elements, together with zinc-group metals and their alloys belong to an emerging class of materials with fascinating characteristics originating from their simultaneous metallic and liquid natures. These metals and alloys are characterised by having low melting points (i.e. between room temperature and 300 °C), making their liquid state accessible to practical applications in various fields of physical chemistry and synthesis. These materials can offer extraordinary capabilities in the synthesis of new materials, catalysis and can also enable novel applications including microfluidics, flexible electronics and drug delivery...
April 3, 2018: Chemical Society Reviews
https://www.readbyqxmd.com/read/29606659/rethinking-dental-school-admission-criteria-correlation-between-pre-admission-variables-and-first-year-performance-for-six-classes-at-one-dental-school
#13
Kevin C Rowland, Susan Rieken
Admissions committees in dental schools are charged with the responsibility of selecting candidates who will succeed in school and become successful members of the profession. Identifying students who will have academic difficulty is challenging. The aim of this study was to determine the predictive value of pre-admission variables for the first-year performance of six classes at one U.S. dental school. The authors hypothesized that the variables undergraduate grade point average (GPA), undergraduate science GPA (biology, chemistry, and physics), and Dental Admission Test (DAT) scores would predict the level of performance achieved in the first year of dental school, measured by year-end GPA...
April 2018: Journal of Dental Education
https://www.readbyqxmd.com/read/29602697/protein-phase-separation-a-new-phase-in-cell-biology
#14
REVIEW
Steven Boeynaems, Simon Alberti, Nicolas L Fawzi, Tanja Mittag, Magdalini Polymenidou, Frederic Rousseau, Joost Schymkowitz, James Shorter, Benjamin Wolozin, Ludo Van Den Bosch, Peter Tompa, Monika Fuxreiter
Cellular compartments and organelles organize biological matter. Most well-known organelles are separated by a membrane boundary from their surrounding milieu. There are also many so-called membraneless organelles and recent studies suggest that these organelles, which are supramolecular assemblies of proteins and RNA molecules, form via protein phase separation. Recent discoveries have shed light on the molecular properties, formation, regulation, and function of membraneless organelles. A combination of techniques from cell biology, biophysics, physical chemistry, structural biology, and bioinformatics are starting to help establish the molecular principles of an emerging field, thus paving the way for exciting discoveries, including novel therapeutic approaches for the treatment of age-related disorders...
March 27, 2018: Trends in Cell Biology
https://www.readbyqxmd.com/read/29602562/design-of-drug-delivery-systems-for-physical-energy-induced-chemical-surgery
#15
Takahiro Nomoto, Nobuhiro Nishiyama
Physical energy-induced chemical surgery, a technique that induces antitumor effects by delivering a drug that exerts a therapeutic effect in response to physical energy and irradiating the diseased part with the corresponding physical energy, is a useful method to treat cancers with minimal systemic side effects. Among chemical surgery, photodynamic therapy (PDT) and neutron capture therapy (NCT) require a system that selectively delivers drugs to the diseased site. Although PDT and NCT have a similar concept, drug delivery systems (DDSs) for their purpose need different functions to solve the unique problems derived from the characteristics of respective physical energy...
March 22, 2018: Biomaterials
https://www.readbyqxmd.com/read/29601758/quantum-simulation-of-electronic-structure-with-linear-depth-and-connectivity
#16
Ian D Kivlichan, Jarrod McClean, Nathan Wiebe, Craig Gidney, Alán Aspuru-Guzik, Garnet Kin-Lic Chan, Ryan Babbush
As physical implementations of quantum architectures emerge, it is increasingly important to consider the cost of algorithms for practical connectivities between qubits. We show that by using an arrangement of gates that we term the fermionic swap network, we can simulate a Trotter step of the electronic structure Hamiltonian in exactly N depth and with N^{2}/2 two-qubit entangling gates, and prepare arbitrary Slater determinants in at most N/2 depth, all assuming only a minimal, linearly connected architecture...
March 16, 2018: Physical Review Letters
https://www.readbyqxmd.com/read/29599808/evidence-based-study-to-compare-daodi-traditional-chinese-medicinal-material-and-non-daodi-traditional-chinese-medicinal-material
#17
REVIEW
Xingyue Yang, Xin Tian, Yannan Zhou, Yali Liu, Xinlong Li, Tingting Lu, Changhe Yu, Liyun He
Background: Daodi medicinal material is widely used in Chinese herb medication. However, there is a lack of systematic methodology for identifying characteristics associated with good quality and reliable efficacy of Daodi med-material. Purpose: The purpose of this study is to provide some evidence to further substantiate the use of Daodi medicinal materials. Methods: Seven relevant databases were searched before July 2014. Two evaluators were responsible for screening and categorizing the results...
2018: Evidence-based Complementary and Alternative Medicine: ECAM
https://www.readbyqxmd.com/read/29597094/membrane-properties-that-shape-the-evolution-of-membrane-enzymes
#18
REVIEW
Charles R Sanders, James M Hutchison
Spectacular recent progress in structural biology has led to determination of the structures of many integral membrane enzymes that catalyze reactions in which at least one substrate also is membrane bound. A pattern of results seems to be emerging in which the active site chemistry of these enzymes is usually found to be analogous to what is observed for water soluble enzymes catalyzing the same reaction types. However, in light of the chemical, structural, and physical complexity of cellular membranes plus the presence of transmembrane gradients and potentials, these enzymes may be subject to membrane-specific regulatory mechanisms that are only now beginning to be uncovered...
March 26, 2018: Current Opinion in Structural Biology
https://www.readbyqxmd.com/read/29589915/tailoring-interfacial-nanoparticle-organization-through-entropy
#19
Guolong Zhu, Zihan Huang, Ziyang Xu, Li-Tang Yan
The ability to tailor the interfacial behaviors of nanoparticles (NPs) is crucial not only for the design of novel nanostructured materials with superior properties and of interest for many promising applications such as water purification, enhanced oil recovery, and innovative energy transduction, but also for a better insight into many biological systems where nanoscale particles such as proteins or viruses can interact and organize at certain interfaces. As a class of emerging building blocks, Janus NPs consisting of two compartments of different chemistry or polarity are ideal candidates to generate tunable and stable interfacial nanostructures because of the asymmetric nature...
March 28, 2018: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29582999/insights-into-the-microstructure-and-transition-mechanism-for-nd-3-doped-bi-4-si-3-o-12-a-promising-near-infrared-laser-material
#20
Feiyang Chen, Meng Ju, Xiaoyu Kuang, Yauyuen Yeung
Due to its unusual optical properties, neodymium ion (Nd3+ )-doped bismuth silicate (Bi4 Si3 O12 , BSO) is widely used for its excellent medium laser amplification in physics, chemistry, biomedicine, and other research fields. Although the spectral transitions and luminescent mechanisms of Nd3+ -doped BSO have been investigated experimentally, theoretical research is severely limited due to the lack of detailed information about the microstructure and the doping site of Nd3+ -doped BSO, as well as the electric and magnetic dipole transition mechanisms...
March 27, 2018: Inorganic Chemistry
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