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ACS Central Science

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https://www.readbyqxmd.com/read/29296677/chemoselective-aliphatic-c-h-bond-oxidation-enabled-by-polarity-reversal
#1
Valeria Dantignana, Michela Milan, Olaf Cussó, Anna Company, Massimo Bietti, Miquel Costas
Methods for selective oxidation of aliphatic C-H bonds are called on to revolutionize organic synthesis by providing novel and more efficient paths. Realization of this goal requires the discovery of mechanisms that can alter in a predictable manner the innate reactivity of these bonds. Ideally, these mechanisms need to make oxidation of aliphatic C-H bonds, which are recognized as relatively inert, compatible with the presence of electron rich functional groups that are highly susceptible to oxidation. Furthermore, predictable modification of the relative reactivity of different C-H bonds within a molecule would enable rapid diversification of the resulting oxidation products...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296676/water-flux-induced-reorientation-of-liquid-crystals
#2
Hadi Ramezani-Dakhel, Monirosadat Sadati, Rui Zhang, Mohammad Rahimi, Khia Kurtenbach, Benoît Roux, Juan J de Pablo
It is well understood that the adsorption of solutes at the interface between a bulk liquid crystal phase and an aqueous phase can lead to orientational or anchoring transitions. A different principle is introduced here, whereby a transient reorientation of a thermotropic liquid crystal is triggered by a spontaneous flux of water across the interface. A critical water flux can be generated by the addition of an electrolyte to the bulk aqueous phase, leading to a change in the solvent activity; water is then transported through the liquid crystal phase and across the interface...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296675/optimizing-chemical-reactions-with-deep-reinforcement-learning
#3
Zhenpeng Zhou, Xiaocheng Li, Richard N Zare
Deep reinforcement learning was employed to optimize chemical reactions. Our model iteratively records the results of a chemical reaction and chooses new experimental conditions to improve the reaction outcome. This model outperformed a state-of-the-art blackbox optimization algorithm by using 71% fewer steps on both simulations and real reactions. Furthermore, we introduced an efficient exploration strategy by drawing the reaction conditions from certain probability distributions, which resulted in an improvement on regret from 0...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296674/dynamic-strategic-bond-analysis-yields-a-ten-step-synthesis-of-20-nor-salvinorin-a-a-potent-%C3%AE%C2%BA-or-agonist
#4
Jeremy J Roach, Yusuke Sasano, Cullen L Schmid, Saheem Zaidi, Vsevolod Katritch, Raymond C Stevens, Laura M Bohn, Ryan A Shenvi
Salvinorin A (SalA) is a plant metabolite that agonizes the human kappa-opioid receptor (κ-OR) with high affinity and high selectivity over mu- and delta-opioid receptors. Its therapeutic potential has stimulated extensive semisynthetic studies and total synthesis campaigns. However, structural modification of SalA has been complicated by its instability, and efficient total synthesis has been frustrated by its dense, complex architecture. Treatment of strategic bonds in SalA as dynamic and dependent on structural perturbation enabled the identification of an efficient retrosynthetic pathway...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296673/glutathione-responsive-selenosulfide-prodrugs-as-a-platform-strategy-for-potent-and-selective-mechanism-based-inhibition-of-protein-tyrosine-phosphatases
#5
Caroline Chandra Tjin, Kate D Otley, Tyler D Baguley, Pradeep Kurup, Jian Xu, Angus C Nairn, Paul J Lombroso, Jonathan A Ellman
Dysregulation of protein tyrosine phosphorylation has been implicated in a number of human diseases, including cancer, diabetes, and neurodegenerative diseases. As a result of their essential role in regulating protein tyrosine phosphorylation levels, protein tyrosine phosphatases (PTPs) have emerged as important yet challenging therapeutic targets. Here we report on the development and application of a glutathione-responsive motif to facilitate the efficient intracellular delivery of a novel class of selenosulfide phosphatase inhibitors for the selective active site directed inhibition of the targeted PTP by selenosulfide exchange with the active site cysteine...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296672/prediction-of-new-stabilizing-mutations-based-on-mechanistic-insights-from-markov-state-models
#6
Maxwell I Zimmerman, Kathryn M Hart, Carrie A Sibbald, Thomas E Frederick, John R Jimah, Catherine R Knoverek, Niraj H Tolia, Gregory R Bowman
Protein stabilization is fundamental to enzyme function and evolution, yet understanding the determinants of a protein's stability remains a challenge. This is largely due to a shortage of atomically detailed models for the ensemble of relevant protein conformations and their relative populations. For example, the M182T substitution in TEM β-lactamase, an enzyme that confers antibiotic resistance to bacteria, is stabilizing but the precise mechanism remains unclear. Here, we employ Markov state models (MSMs) to uncover how M182T shifts the distribution of different structures that TEM adopts...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296671/synthesis-of-diverse-11-and-12-membered-macrolactones-from-a-common-linear-substrate-using-a-single-biocatalyst
#7
Michael M Gilbert, Matthew D DeMars, Song Yang, Jessica M Grandner, Shoulei Wang, Hengbin Wang, Alison R H Narayan, David H Sherman, K N Houk, John Montgomery
The diversification of late stage synthetic intermediates provides significant advantages in efficiency in comparison to conventional linear approaches. Despite these advantages, accessing varying ring scaffolds and functional group patterns from a common intermediate poses considerable challenges using existing methods. The combination of regiodivergent nickel-catalyzed C-C couplings and site-selective biocatalytic C-H oxidations using the cytochrome P450 enzyme PikC addresses this problem by enabling a single late-stage linear intermediate to be converted to macrolactones of differing ring size and with diverse patterns of oxidation...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296670/dynamic-light-scattering-microrheology-reveals-multiscale-viscoelasticity-of-polymer-gels-and-precious-biological-materials
#8
Brad A Krajina, Carolina Tropini, Audrey Zhu, Philip DiGiacomo, Justin L Sonnenburg, Sarah C Heilshorn, Andrew J Spakowitz
The development of experimental techniques capable of probing the viscoelasticity of soft materials over a broad range of time scales is essential to uncovering the physics that governs their behavior. In this work, we develop a microrheology technique that requires only 12 μL of sample and is capable of resolving dynamic behavior ranging in time scales from 10-6 to 10 s. Our approach, based on dynamic light scattering in the single-scattering limit, enables the study of polymer gels and other soft materials over a vastly larger hierarchy of time scales than macrorheology measurements...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296669/theoretical-investigations-of-the-electrochemical-reduction-of-co-on-single-metal-atoms-embedded-in-graphene
#9
Charlotte Kirk, Leanne D Chen, Samira Siahrostami, Mohammadreza Karamad, Michal Bajdich, Johannes Voss, Jens K Nørskov, Karen Chan
Single transition metal atoms embedded at single vacancies of graphene provide a unique paradigm for catalytic reactions. We present a density functional theory study of such systems for the electrochemical reduction of CO. Theoretical investigations of CO electrochemical reduction are particularly challenging in that electrochemical activation energies are a necessary descriptor of activity. We determined the electrochemical barriers for key proton-electron transfer steps using a state-of-the-art, fully explicit solvent model of the electrochemical interface...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296668/chemical-proteomics-identifies-slc25a20-as-a-functional-target-of-the-ingenol-class-of-actinic-keratosis-drugs
#10
Christopher G Parker, Christian A Kuttruff, Andrea Galmozzi, Lars Jørgensen, Chien-Hung Yeh, Daniel J Hermanson, Yujia Wang, Marta Artola, Steven J McKerrall, Christopher M Josyln, Bjarne Nørremark, Georg Dünstl, Jakob Felding, Enrique Saez, Phil S Baran, Benjamin F Cravatt
The diterpenoid ester ingenol mebutate (IngMeb) is the active ingredient in the topical drug Picato, a first-in-class treatment for the precancerous skin condition actinic keratosis. IngMeb is proposed to exert its therapeutic effects through a dual mode of action involving (i) induction of cell death that is associated with mitochondrial dysfunction followed by (ii) stimulation of a local inflammatory response, at least partially driven by protein kinase C (PKC) activation. Although this therapeutic model has been well characterized, the complete set of molecular targets responsible for mediating IngMeb activity remains ill-defined...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296667/cooperative-co2-absorption-isotherms-from-a-bifunctional-guanidine-and-bifunctional-alcohol
#11
Rachel Steinhardt, Stanley C Hiew, Hemakesh Mohapatra, Du Nguyen, Zachary Oh, Richard Truong, Aaron Esser-Kahn
Designing new liquids for CO2 absorption is a challenge in CO2 removal. Here, achieving low regeneration energies while keeping high selectivity and large capacity are current challenges. Recent cooperative metal-organic frameworks have shown the potential to address many of these challenges. However, many absorbent systems and designs rely on liquid capture agents. We present herein a liquid absorption system which exhibits cooperative CO2 absorption isotherms. Upon introduction, CO2 uptake is initially suppressed, followed by an abrupt increase in absorption...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296666/the-enhancement-of-interfacial-exciton-dissociation-by-energetic-disorder-is-a-nonequilibrium-effect
#12
Liang Shi, Chee Kong Lee, Adam P Willard
The dissociation of excited electron-hole pairs is a microscopic process that is fundamental to the performance of photovoltaic systems. For this process to be successful, the oppositely charged electron and hole must overcome an electrostatic binding energy before they undergo ground state recombination. It has been observed previously that the presence of energetic disorder can lead to a reduction in recombination losses. Here we investigate this effect using a simple model of charge dynamics at a donor-acceptor interface...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296665/parallel-screening-for-rapid-identification-of-orthogonal-bioluminescent-tools
#13
Colin M Rathbun, William B Porterfield, Krysten A Jones, Marian J Sagoe, Monique R Reyes, Christine T Hua, Jennifer A Prescher
Bioluminescence imaging with luciferase enzymes and luciferin small molecules is a well-established technique for tracking cells and other biological features in rodent models. Despite its popularity, bioluminescence has long been hindered by a lack of distinguishable probes. Here we present a method to rapidly identify new substrate-selective luciferases for multicomponent imaging. Our strategy relies on parallel screening of luciferin analogues with panels of mutant enzymes. The compiled data set is then analyzed in silico to uncover mutually orthogonal sets...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296664/long-range-organization-of-membrane-curving-proteins
#14
Mijo Simunovic, Anđela Šarić, J Michael Henderson, Ka Yee C Lee, Gregory A Voth
Biological membranes have a central role in mediating the organization of membrane-curving proteins, a dynamic process that has proven to be challenging to probe experimentally. Using atomic force microscopy, we capture the hierarchically organized assemblies of Bin/amphiphysin/Rvs (BAR) proteins on supported lipid membranes. Their structure reveals distinct long linear aggregates of proteins, regularly spaced by up to 300 nm. Employing accurate free-energy calculations from large-scale coarse-grained computer simulations, we found that the membrane mediates the interaction among protein filaments as a combination of short- and long-ranged interactions...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296663/computer-assisted-retrosynthesis-based-on-molecular-similarity
#15
Connor W Coley, Luke Rogers, William H Green, Klavs F Jensen
We demonstrate molecular similarity to be a surprisingly effective metric for proposing and ranking one-step retrosynthetic disconnections based on analogy to precedent reactions. The developed approach mimics the retrosynthetic strategy defined implicitly by a corpus of known reactions without the need to encode any chemical knowledge. Using 40 000 reactions from the patent literature as a knowledge base, the recorded reactants are among the top 10 proposed precursors in 74.1% of 5000 test reactions, providing strong quantitative support for our methodology...
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296662/diversifying-the-glowing-bioluminescent-toolbox
#16
Marie C Heffern
No abstract text is available yet for this article.
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296661/taking-aim-at-poaching-with-tissue-engineering
#17
Melissa Pandika
No abstract text is available yet for this article.
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29296660/a-conversation-with-nathan-allen
#18
Andrea Widener
No abstract text is available yet for this article.
December 27, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29202024/highly-active-fe-sites-in-ultrathin-pyrrhotite-fe7s8-nanosheets-realizing-efficient-electrocatalytic-oxygen-evolution
#19
Shichuan Chen, Zhixiong Kang, Xiaodong Zhang, Junfeng Xie, Hui Wang, Wei Shao, XuSheng Zheng, Wensheng Yan, Bicai Pan, Yi Xie
Identification of active sites in an electrocatalyst is essential for understanding of the mechanism of electrocatalytic water splitting. To be one of the most active oxygen evolution reaction catalysts in alkaline media, Ni-Fe based compounds have attracted tremendous attention, while the role of Ni and Fe sites played has still come under debate. Herein, by taking the pyrrhotite Fe7S8 nanosheets with mixed-valence states and metallic conductivity for examples, we illustrate that Fe could be a highly active site for electrocatalytic oxygen evolution...
November 22, 2017: ACS Central Science
https://www.readbyqxmd.com/read/29202023/combating-drug-resistant-mutants-of-anaplastic-lymphoma-kinase-with-potent-and-selective-type-i1-2-inhibitors-by-stabilizing-unique-dfg-shifted-loop-conformation
#20
Peichen Pan, Huidong Yu, Qinglan Liu, Xiaotian Kong, Hu Chen, Jiean Chen, Qi Liu, Dan Li, Yu Kang, Huiyong Sun, Wenfang Zhou, Sheng Tian, Sunliang Cui, Feng Zhu, Youyong Li, Yong Huang, Tingjun Hou
Targeted inhibition of anaplastic lymphoma kinase (ALK) dramatically improved therapeutic outcomes in the treatment of ALK-positive cancers, but unfortunately patients invariably progressed due to acquired resistance mutations in ALK. Currently available drugs are all type-I inhibitors bound to the ATP-binding pocket and are most likely to be resistant in patients harboring genetic mutations surrounding the ATP pocket. To overcome drug resistance, we rationally designed a novel kind of "bridge" inhibitor, which specially bind into an extended hydrophobic back pocket adjacent to the ATP-binding site of ALK...
November 22, 2017: ACS Central Science
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