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https://www.readbyqxmd.com/read/29974074/rationalization-of-asymmetric-amplification-via-autocatalysis-triggered-by-isotopically-chiral-molecules
#1
Neil A Hawbaker, Donna G Blackmond
Asymmetric amplification induced in the Soai autocatalytic reaction by chiral initiators that are enantiomeric only by virtue of an isotope, e.g., -CH3 vs CD3 -, is examined by spectroscopic, kinetic, and DFT modeling studies to help understand requirements for the emergence of biological homochirality. We find that the initiator inhibit s the autocatalytic pathway at the outset of the reaction but ultimately provides the imbalance required for asymmetric amplification. This work provides clues in the ongoing search for prebiotically plausible versions of asymmetric autocatalysis...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974073/delineating-physical-organic-parameters-in-site-selective-c-h-functionalization-of-indoles
#2
Youyoung Kim, Yoonsu Park, Sukbok Chang
Site-selective C-H functionalization is a great challenge in homogeneous transition-metal catalysis. Herein, we present a physical organic approach to delineate the origin of regioselective amidation of N -acylindoles through Ir(III) catalysis. Bulkiness of N -directing groups of indole substrates and electronics of carboxylate additives were identified as two major factors in controlling C2 and C7 selectivity, and their microscopic mechanisms were studied with DFT-based transition state analysis. Computational insights led us to interrogate a linear free energy relationship, and parametrization of molecular determinants enabled the establishment of an intuitive yet robust statistical model that correlates an extensive number of validation data points in high accuracy...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974072/the-molecular-basis-for-inhibition-of-stemlike-cancer-cells-by-salinomycin
#3
Xiaoli Huang, Björn Borgström, John Stegmayr, Yasmin Abassi, Monika Kruszyk, Hakon Leffler, Lo Persson, Sebastian Albinsson, Ramin Massoumi, Ivan G Scheblykin, Cecilia Hegardt, Stina Oredsson, Daniel Strand
Tumors are phenotypically heterogeneous and include subpopulations of cancer cells with stemlike properties. The natural product salinomycin, a K+ -selective ionophore, was recently found to exert selectivity against such cancer stem cells. This selective effect is thought to be due to inhibition of the Wnt signaling pathway, but the mechanistic basis remains unclear. Here, we develop a functionally competent fluorescent conjugate of salinomycin to investigate the molecular mechanism of this compound. By subcellular imaging, we demonstrate a rapid cellular uptake of the conjugate and accumulation in the endoplasmic reticulum (ER)...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974071/taming-the-strength-of-interfacial-interactions-via-nanoconfinement
#4
David Nieto Simavilla, Weide Huang, Caroline Housmans, Michele Sferrazza, Simone Napolitano
The interaction between two immiscible materials is related to the number of contacts per unit area formed by the two materials. For practical reasons, this information is often parametrized by the interfacial free energy, which is commonly derived via rather cumbersome approaches, where properties of the interface are described by combining surface parameters of the single materials. These combining rules , however, neglect any effect that geometry might have on the strength of the interfacial interaction...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974070/surface-pore-engineering-of-covalent-organic-frameworks-for-ammonia-capture-through-synergistic-multivariate-and-open-metal-site-approaches
#5
Yajie Yang, Muhammad Faheem, Lili Wang, Qinghao Meng, Haoyan Sha, Nan Yang, Ye Yuan, Guangshan Zhu
Ammonia (NH3 ) is a commonly used industrial gas, but its corrosiveness and toxicity are hazardous to human health. Although many adsorbents have been investigated for NH3 sorption, limited ammonia uptake remains an urgent issue yet to be solved. In this article, a series of multivariate covalent organic frameworks (COFs) are explored which are densely functionalized with various active groups, such as -N-H, -C=O, and carboxyl group. Then, a metal ion (Ca2+ , Mn2+ , and Sr2+ ) is integrated into the carboxylated structure achieving the first case of an open metal site in COF architecture...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974069/outer-sphere-water-clusters-tune-the-lanthanide-selectivity-of-diglycolamides
#6
Anna G Baldwin, Alexander S Ivanov, Neil J Williams, Ross J Ellis, Bruce A Moyer, Vyacheslav S Bryantsev, Jenifer C Shafer
Fundamental understanding of the selective recognition and separation of f -block metal ions by chelating agents is of crucial importance for advancing sustainable energy systems. Current investigations in this area are mostly focused on the study of inner-sphere interactions between metal ions and donor groups of ligands, while the effects on the selectivity resulting from molecular interactions in the outer-sphere region have been largely overlooked. Herein, we explore the fundamental origins of the selectivity of the solvating extractant N , N , N ', N '-tetraoctyl diglycolamide (TODGA) for adjacent lanthanides in a liquid-liquid extraction system, which is of relevance to nuclear fuel reprocessing and rare-earth refining technologies...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974068/tuning-the-bandgap-of-photo-sensitive-polydopamine-ag-3-po-4-graphene-oxide-coating-for-rapid-noninvasive-disinfection-of-implants
#7
Xianzhou Xie, Congyang Mao, Xiangmei Liu, Lei Tan, Zhenduo Cui, Xianjin Yang, Shengli Zhu, Zhaoyang Li, Xubo Yuan, Yufeng Zheng, Kelvin Wai Kwok Yeung, Paul K Chu, Shuilin Wu
Bacterial infection and associated complications are threats to human health especially when biofilms form on biomedical devices and artificial implants. Herein, a hybrid polydopamine (PDA)/Ag3 PO4 /graphene oxide (GO) coating is designed and constructed to achieve rapid bacteria killing and eliminate biofilms in situ. By varying the amount of GO in the hybrid coating, the bandgap can be tuned from 2.52 to 2.0 eV so that irradiation with 660 nm visible light produces bacteria-killing effects synergistically in concert with reactive oxygen species (ROS)...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974067/confinement-of-therapeutic-enzymes-in-selectively-permeable-polymer-vesicles-by-polymerization-induced-self-assembly-pisa-reduces-antibody-binding-and-proteolytic-susceptibility
#8
Lewis D Blackman, Spyridon Varlas, Maria C Arno, Zachary H Houston, Nicholas L Fletcher, Kristofer J Thurecht, Muhammad Hasan, Matthew I Gibson, Rachel K O'Reilly
Covalent PEGylation of biologics has been widely employed to reduce immunogenicity, while improving stability and half-life in vivo . This approach requires covalent protein modification, creating a new entity. An alternative approach is stabilization by encapsulation into polymersomes; however this typically requires multiple steps, and the segregation requires the vesicles to be permeable to retain function. Herein, we demonstrate the one-pot synthesis of therapeutic enzyme-loaded vesicles with size-selective permeability using polymerization-induced self-assembly (PISA) enabling the encapsulated enzyme to function from within a confined domain...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974066/lipid-protein-interactions-are-unique-fingerprints-for-membrane-proteins
#9
Valentina Corradi, Eduardo Mendez-Villuendas, Helgi I Ingólfsson, Ruo-Xu Gu, Iwona Siuda, Manuel N Melo, Anastassiia Moussatova, Lucien J DeGagné, Besian I Sejdiu, Gurpreet Singh, Tsjerk A Wassenaar, Karelia Delgado Magnero, Siewert J Marrink, D Peter Tieleman
Cell membranes contain hundreds of different proteins and lipids in an asymmetric arrangement. Our current understanding of the detailed organization of cell membranes remains rather elusive, because of the challenge to study fluctuating nanoscale assemblies of lipids and proteins with the required spatiotemporal resolution. Here, we use molecular dynamics simulations to characterize the lipid environment of 10 different membrane proteins. To provide a realistic lipid environment, the proteins are embedded in a model plasma membrane, where more than 60 lipid species are represented, asymmetrically distributed between the leaflets...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974065/from-tree-to-tape-direct-synthesis-of-pressure-sensitive-adhesives-from-depolymerized-raw-lignocellulosic-biomass
#10
Shu Wang, Li Shuai, Basudeb Saha, Dionisios G Vlachos, Thomas H Epps
We report a new and robust strategy toward the development of high-performance pressure sensitive adhesives (PSAs) from chemicals directly obtained from raw biomass deconstruction. A particularly unique and translatable aspect of this work was the use of a monomer obtained from real biomass, as opposed to a model compound or lignin-mimic, to generate well-defined and nanostructure-forming polymers. Herein, poplar wood depolymerization followed by minimal purification steps (filtration and extraction) produced two aromatic compounds, 4-propylsyringol and 4-propylguaiacol, with high purity and yield...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974064/coarctate-and-m%C3%A3-bius-the-helical-orbitals-of-allene-and-other-cumulenes
#11
Marc H Garner, Roald Hoffmann, Sten Rettrup, Gemma C Solomon
As brought to the attention of the community by Hendon et al. and noted by previous workers, the π orbitals of the equilibrium geometry odd-carbon (even number of double bonds = n ) [ n ]cumulenes may be written in either rectilinear or helical form. We trace the origins and detailed composition of the helical orbitals of cumulenes, which emerge in the simplest Hückel model and are not much modified in advanced computations. For the α,ω-disubstituted even [ n ]cumulenes, the helical representation is obligatory as the symmetry is reduced from D 2 d to C 2 ...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974063/splicerca-in-situ-single-cell-analysis-of-mrna-splicing-variants
#12
Xiaojun Ren, Ruijie Deng, Kaixiang Zhang, Yupeng Sun, Xucong Teng, Jinghong Li
Immune cell heterogeneity due to the differential expression of RNA splicing variants still remains unexplored. This is mainly because single-cell imaging technologies of splicing variants with precise sequence or base resolution are now not readily available. Herein, we design a splice-junction anchored padlock-probe-mediated rolling circle amplification assay (SpliceRCA) for single-cell imaging of splice isoforms of essential regulatory immune gene (CD45) upon T-cell activation. Two recognition regions in the padlock probe can target the splice-junction sequence, resulting in a close proximity for triggering in situ one-target-one-amplicon amplification...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974062/all-inorganic-metal-halide-perovskite-nanocrystals-opportunities-and-challenges
#13
REVIEW
Qiao Zhang, Yadong Yin
The past decade has witnessed the growing interest in metal halide perovskites as driven by their promising applications in diverse fields. The low intrinsic stability of the early developed organic versions has however hampered their widespread applications. Very recently, all-inorganic perovskite nanocrystals have emerged as a new class of materials that hold great promise for the practical applications in solar cells, photodetectors, light-emitting diodes, and lasers, among others. In this Outlook, we first discuss the recent developments in the preparation, properties, and applications of all-inorganic metal halide perovskite nanocrystals, with a particular focus on CsPbX3 , and then provide our view of current challenges and future directions in this emerging area...
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974061/programming-framework-materials-for-ammonia-capture
#14
Adam J Rieth, Mircea Dincă
No abstract text is available yet for this article.
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974060/one-handed-helical-orbitals-in-conjugated-molecules
#15
Yuriko Aoki, Yuuichi Orimoto, Akira Imamura
No abstract text is available yet for this article.
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29974059/a-conversation-with-amy-prieto
#16
Prachi Patel
No abstract text is available yet for this article.
June 27, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29806014/correction-to-molecular-caging-of-graphene-with-cyclohexane-transfer-and-electrical-transport
#17
Liubov A Belyaeva, Wangyang Fu, Hadi Arjmandi-Tash, Grégory F Schneider
[This corrects the article DOI: 10.1021/acscentsci.6b00236.].
May 23, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29806013/catalyst-controlled-stereodivergent-synthesis-of-atropisomeric-multiaxis-systems
#18
Dominik Lotter, Alessandro Castrogiovanni, Markus Neuburger, Christof Sparr
Molecular scaffolds with multiple rotationally restricted bonds allow a precise spatial positioning of functional groups. However, their synthesis requires methods addressing the configuration of each stereogenic axis. We report here a catalyst-stereocontrolled synthesis of atropisomeric multiaxis systems enabling divergence from the prevailing stereochemical reaction path. By using ion-pairing catalysts in arene-forming aldol condensations, a strong substrate-induced stereopreference can be overcome to provide structurally well-defined helical oligo-1,2-naphthylenes...
May 23, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29806012/slow-dynamics-around-a-protein-and-its-coupling-to-solvent
#19
Yun-Hsuan Kuo, Yun-Wei Chiang
Solvent is essential for protein dynamics and function, but its role in regulating the dynamics remains debated. Here, we employ saturation transfer electron spin resonance (ST-ESR) to explore the issue and characterize the dynamics on a longer (from μs to s) time scale than has been extensively studied. We first demonstrate the reliability of ST-ESR by showing that the dynamical changeovers revealed in the spectra agree to liquid-liquid transition (LLT) in the state diagram of the glycerol/water system. Then, we utilize ST-ESR with four different probes to systematically map out the variation in local (site-specific) dynamics around a protein surface at subfreezing temperatures (180-240 K) in 10 mol % glycerol/water mixtures...
May 23, 2018: ACS Central Science
https://www.readbyqxmd.com/read/29806011/molecular-origin-of-the-glass-transition-in-polyelectrolyte-assemblies
#20
Yanpu Zhang, Piotr Batys, Joshua T O'Neal, Fei Li, Maria Sammalkorpi, Jodie L Lutkenhaus
Water plays a central role in the assembly and the dynamics of charged systems such as proteins, enzymes, DNA, and surfactants. Yet it remains a challenge to resolve how water affects relaxation at a molecular level, particularly for assemblies of oppositely charged macromolecules. Here, the molecular origin of water's influence on the glass transition is quantified for several charged macromolecular systems. It is revealed that the glass transition temperature ( T g ) is controlled by the number of water molecules surrounding an oppositely charged polyelectrolyte-polyelectrolyte intrinsic ion pair as 1/ T g ∼ ln( n H2 O / n intrinsic ion pair )...
May 23, 2018: ACS Central Science
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