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Accounts of Chemical Research

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https://www.readbyqxmd.com/read/28426203/tyrosine-kinase-activation-and-conformational-flexibility-lessons-from-src-family-tyrosine-kinases
#1
Yilin Meng, Matthew P Pond, Benoît Roux
Protein kinases are enzymes that catalyze the covalent transfer of the γ-phosphate of an adenosine triphosphate (ATP) molecule onto a tyrosine, serine, threonine, or histidine residue in the substrate and thus send a chemical signal to networks of downstream proteins. They are important cellular signaling enzymes that regulate cell growth, proliferation, metabolism, differentiation, and migration. Unregulated protein kinase activity is often associated with a wide range of diseases, therefore making protein kinases major therapeutic targets...
April 20, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28418642/structure-and-dynamics-of-individual-diastereomeric-complexes-on-platinum-surface-studies-related-to-heterogeneous-enantioselective-catalysis
#2
Yi Dong, Guillaume Goubert, Michael N Groves, Jean-Christian Lemay, Bjørk Hammer, Peter H McBreen
The modification of heterogeneous catalysts through the chemisorption of chiral molecules is a method to create catalytic sites for enantioselective surface reactions. The chiral molecule is called a chiral modifier by analogy to the terms chiral auxiliary or chiral ligand used in homogeneous asymmetric catalysis. While there has been progress in understanding how chirality transfer occurs, the intrinsic difficulties in determining enantioselective reaction mechanisms are compounded by the multisite nature of heterogeneous catalysts and by the challenges facing stereospecific surface analysis...
April 18, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28406290/cooperative-catalysis-at-metal-sulfur-bonds
#3
Lukas Omann, C David F Königs, Hendrik F T Klare, Martin Oestreich
Cooperative catalysis has attracted tremendous attention in recent years, emerging as a key strategy for the development of novel atom-economic and environmentally more benign catalytic processes. In particular, Noyori-type complexes with metal-nitrogen bonds have been extensively studied and evolved as privileged catalysts in hydrogenation chemistry. In contrast, catalysts containing metal-sulfur bonds as the reactive site are out of the ordinary, despite their abundance in living systems, where they are assumed to play a key role in biologically relevant processes...
April 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28406029/co2-water-rock-wettability-variability-influencing-factors-and-implications-for-co2-geostorage
#4
Stefan Iglauer
Carbon geosequestration (CGS) has been identified as a key technology to reduce anthropogenic greenhouse gas emissions and thus significantly mitigate climate change. In CGS, CO2 is captured from large point-source emitters (e.g., coal fired power stations), purified, and injected deep underground into geological formations for disposal. However, the CO2 has a lower density than the resident formation brine and thus migrates upward due to buoyancy forces. To prevent the CO2 from leaking back to the surface, four trapping mechanisms are used: (1) structural trapping (where a tight caprock acts as a seal barrier through which the CO2 cannot percolate), (2) residual trapping (where the CO2 plume is split into many micrometer-sized bubbles, which are immobilized by capillary forces in the pore network of the rock), (3) dissolution trapping (where CO2 dissolves in the formation brine and sinks deep into the reservoir due to a slight increase in brine density), and (4) mineral trapping (where the CO2 introduced into the subsurface chemically reacts with the formation brine or reservoir rock or both to form solid precipitates)...
April 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28383245/exploring-the-chemistry-of-genetic-information-storage-and-propagation-through-polymerase-engineering
#5
Gillian Houlihan, Sebastian Arangundy-Franklin, Philipp Holliger
Nucleic acids are a distinct form of sequence-defined biopolymer. What sets them apart from other biopolymers such as polypeptides or polysaccharides is their unique capacity to encode, store, and propagate genetic information (molecular heredity). In nature, just two closely related nucleic acids, DNA and RNA, function as repositories and carriers of genetic information. They therefore are the molecular embodiment of biological information. This naturally leads to questions regarding the degree of variation from this seemingly ideal "Goldilocks" chemistry that would still be compatible with the fundamental property of molecular heredity...
April 6, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28379012/phase-transfer-and-ion-pairing-catalysis-of-pentanidiums-and-bisguanidiniums
#6
Lili Zong, Choon-Hong Tan
Catalysts accelerate biological processes and organic reactions in a controlled and selective fashion. There are continuing efforts in asymmetric catalysis to develop efficient catalysts with broad reaction scope and industrial practicability. Among the various modes of asymmetric catalysis, phase-transfer catalysis has attracted intense interest due to its facile scale up and low catalyst loading. Chiral quaternary ammonium and phosphonium salts are well-studied classes of chiral phase-transfer catalysts, and they are typically composed of sp(3)-hybridized quaternary onium salts...
April 5, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28378591/semiconductor-photocatalysis-for-chemoselective-radical-coupling-reactions
#7
Horst Kisch
Photocatalysis at semiconductor surfaces is a growing field of general photocatalysis because of its importance for the chemical utilization of solar energy. By analogy with photoelectrochemistry the basic mechanism of semiconductor photocatalysis can be broken down into three steps: photogenerated formation of surface redox centers (electron-hole pairs), interfacial electron transfer from and to substrates (often coupled with proton-transfer), and conversion of primary redox intermediates into the products...
April 5, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28375627/ring-construction-by-palladium-0-catalyzed-c-sp-3-h-activation
#8
Olivier Baudoin
The catalytic activation and functionalization of unactivated C(sp(3))-H bonds of alkyl groups has undergone intense development in recent years. In particular, a variety of directing groups as well as native functional groups have been employed in combination with palladium(II) catalysis in order to perform a variety of intermolecular, and to some extent intramolecular reactions. In parallel, inspired by precedents in C(sp(2))-H arylation, our group and others have developed a different approach, which is the focus of this Account...
April 4, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28375613/thieno-3-4-b-thiophene-based-novel-small-molecule-optoelectronic-materials
#9
Cheng Zhang, Xiaozhang Zhu
Because of the tailorable photoelectric properties derived from judicious molecular design and large-area and low-temperature processability especially on flexible substrates, design and synthesis of new organic π-functional materials is always a central topic in the field of organic optoelectronics, which siginificantly contributed to the development of high-performance optoelectronic devices such as organic photovoltaics (OPVs), organic field-effect transistors (OFETs), and organic light-emitting diodes (OLEDs)...
April 4, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28374998/iridium-catalyzed-asymmetric-hydrogenation-of-unsaturated-carboxylic-acids
#10
Shou-Fei Zhu, Qi-Lin Zhou
Chiral carboxylic acid moieties are widely found in pharmaceuticals, agrochemicals, flavors, fragrances, and health supplements. Although they can be synthesized straightforwardly by transition-metal-catalyzed enantioselective hydrogenation of unsaturated carboxylic acids, because the existing chiral catalysts have various disadvantages, the development of new chiral catalysts with high activity and enantioselectivity is an important, long-standing challenge. Ruthenium complexes with chiral diphosphine ligands and rhodium complexes with chiral monodentate or bidentate phosphorus ligands have been the predominant catalysts for asymmetric hydrogenation of unsaturated acids...
April 4, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28374993/removable-backbone-modification-method-for-the-chemical-synthesis-of-membrane-proteins
#11
Jia-Bin Li, Shan Tang, Ji-Shen Zheng, Chang-Lin Tian, Lei Liu
Chemical synthesis can produce water-soluble globular proteins bearing specifically designed modifications. These synthetic molecules have been used to study the biological functions of proteins and to improve the pharmacological properties of protein drugs. However, the above advances notwithstanding, membrane proteins (MPs), which comprise 20-30% of all proteins in the proteomes of most eukaryotic cells, remain elusive with regard to chemical synthesis. This difficulty stems from the strong hydrophobic character of MPs, which can cause considerable handling issues during ligation, purification, and characterization steps...
April 4, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28362082/pore-scale-geochemical-reactivity-associated-with-co2-storage-new-frontiers-at-the-fluid-solid-interface
#12
Catherine Noiriel, Damien Daval
The reactivity of carbonate and silicate minerals is at the heart of porosity and pore geometry changes in rocks injected with CO2, which ultimately control the evolution of flow and transport properties of fluids in porous and/or fractured geological reservoirs. Modeling the dynamics of CO2-water-rock interactions is challenging because of the resulting large geochemical disequilibrium, the reservoir heterogeneities, and the large space and time scales involved in the processes. In particular, there is a lack of information about how the macroscopic properties of a reservoir, e...
March 31, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28358486/separation-of-semiconducting-carbon-nanotubes-for-flexible-and-stretchable-electronics-using-polymer-removable-method
#13
Ting Lei, Igor Pochorovski, Zhenan Bao
Electronics that are soft, conformal, and stretchable are highly desirable for wearable electronics, prosthetics, and robotics. Among the various available electronic materials, single walled carbon nanotubes (SWNTs) and their network have exhibited high mechanical flexibility and stretchability, along with comparable electrical performance to traditional rigid materials, e.g. polysilicon and metal oxides. Unfortunately, SWNTs produced en masse contain a mixture of semiconducting (s-) and metallic (m-) SWNTs, rendering them unsuitable for electronic applications...
March 30, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28355077/isothermal-amplification-for-microrna-detection-from-the-test-tube-to-the-cell
#14
Ruijie Deng, Kaixiang Zhang, Jinghong Li
MicroRNAs (miRNAs) are a class of small noncoding RNAs that act as pivotal post-transcriptional regulators of gene expression, thus involving in many fundamental cellular processes such as cell proliferation, migration, and canceration. The detection of miRNAs has attracted significant interest, as abnormal miRNA expression is identified to contribute to serious human diseases such as cancers. Particularly, miRNAs in peripheral blood have recently been recognized as important biomarkers potential for liquid biopsy...
March 29, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28353338/proton-based-ultrafast-magic-angle-spinning-solid-state-nmr-spectroscopy
#15
Rongchun Zhang, Kamal H Mroue, Ayyalusamy Ramamoorthy
Protons are vastly abundant in a wide range of exciting macromolecules and thus can be a powerful probe to investigate the structure and dynamics at atomic resolution using solid-state NMR (ssNMR) spectroscopy. Unfortunately, the high signal sensitivity, afforded by the high natural-abundance and high gyromagnetic ratio of protons, is greatly compromised by severe line broadening due to the very strong (1)H-(1)H dipolar couplings. As a result, protons are rarely used, in spite of the desperate need for enhancing the sensitivity of ssNMR to study a variety of systems that are not amenable for high resolution investigation using other techniques including X-ray crystallography, cryo-electron microscopy, and solution NMR spectroscopy...
March 29, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28350434/stepwise-synthesis-of-metal-organic-frameworks
#16
Mathieu Bosch, Shuai Yuan, William Rutledge, Hong-Cai Zhou
Metal-organic frameworks (MOFs) are a category of porous materials that offer unparalleled control over their surface areas (demonstrated as higher than for any other material), pore characteristics, and functionalization. This allows them to be customized for exceptional performance in a wide variety of applications, most commonly including gas storage and separation, drug delivery, luminescence, or heterogeneous catalysis. In order to optimize biomimicry, controlled separations and storage of small molecules, and detailed testing of structure-property relationships, one major goal of MOF research is "rational design" or "pore engineering", or precise control of the placement of multiple functional groups in pores of chosen sizes and shapes...
March 28, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28350161/multiparametric-atomic-force-microscopy-imaging-of-biomolecular-and-cellular-systems
#17
David Alsteens, Daniel J Müller, Yves F Dufrêne
There is a need in biochemical research for new tools that can image and manipulate biomolecular and cellular systems at the nanoscale. During the past decades, there has been tremendous progress in developing atomic force microscopy (AFM) techniques to analyze biosystems, down to the single-molecule level. Force-distance (FD) curve-based AFM in particular has enabled researchers to map and quantify biophysical properties and biomolecular interactions on a wide variety of specimens. Despite its great potential, this AFM method has long been limited by its low spatial and temporal resolutions...
March 28, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28345881/silane-and-germane-molecular-electronics
#18
Timothy A Su, Haixing Li, Rebekka S Klausen, Nathaniel T Kim, Madhav Neupane, James L Leighton, Michael L Steigerwald, Latha Venkataraman, Colin Nuckolls
This Account provides an overview of our recent efforts to uncover the fundamental charge transport properties of Si-Si and Ge-Ge single bonds and introduce useful functions into group 14 molecular wires. We utilize the tools of chemical synthesis and a scanning tunneling microscopy-based break-junction technique to study the mechanism of charge transport in these molecular systems. We evaluated the fundamental ability of silicon, germanium, and carbon molecular wires to transport charge by comparing conductances within families of well-defined structures, the members of which differ only in the number of Si (or Ge or C) atoms in the wire...
March 27, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28345879/vibrational-probes-from-small-molecule-solvatochromism-theory-and-experiments-to-applications-in-complex-systems
#19
Bartosz Błasiak, Casey H Londergan, Lauren J Webb, Minhaeng Cho
The vibrational frequency of a chosen normal mode is one of the most accurately measurable spectroscopic properties of molecules in condensed phases. Accordingly, infrared absorption and Raman scattering spectroscopy have provided valuable information on both distributions and ensemble-average values of molecular vibrational frequencies, and these frequencies are now routinely used to investigate structure, conformation, and even absolute configuration of chemical and biological molecules of interest. Recent advancements in coherent time-domain nonlinear vibrational spectroscopy have allowed the study of heterogeneous distributions of local structures and thermally driven ultrafast fluctuations of vibrational frequencies...
March 27, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28345876/engineering-cellular-microenvironments-with-photo-and-enzymatically-responsive-hydrogels-toward-biomimetic-3d-cell-culture-models
#20
Roger Y Tam, Laura J Smith, Molly S Shoichet
Conventional cell culture techniques using 2D polystyrene or glass have provided great insight into key biochemical mechanisms responsible for cellular events such as cell proliferation, differentiation, and cell-cell interactions. However, the physical and chemical properties of 2D culture in vitro are dramatically different than those found in the native cellular microenvironment in vivo. Cells grown on 2D substrates differ significantly from those grown in vivo, and this explains, in part, why many promising drug candidates discovered through in vitro drug screening assays fail when they are translated to in vivo animal or human models...
March 27, 2017: Accounts of Chemical Research
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