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ACS Central Science

Catherine R Mulzer, Luxi Shen, Ryan P Bisbey, James R McKone, Na Zhang, Héctor D Abruña, William R Dichtel
The low conductivity of two-dimensional covalent organic frameworks (2D COFs), and most related coordination polymers, limits their applicability in optoelectronic and electrical energy storage (EES) devices. Although some networks exhibit promising conductivity, these examples generally lack structural versatility, one of the most attractive features of framework materials design. Here we enhance the electrical conductivity of a redox-active 2D COF film by electropolymerizing 3,4-ethylenedioxythiophene (EDOT) within its pores...
September 28, 2016: ACS Central Science
Joshua Lequieu, Andrés Córdoba, David C Schwartz, Juan J de Pablo
Nucleosomes form the basic unit of compaction within eukaryotic genomes, and their locations represent an important, yet poorly understood, mechanism of genetic regulation. Quantifying the strength of interactions within the nucleosome is a central problem in biophysics and is critical to understanding how nucleosome positions influence gene expression. By comparing to single-molecule experiments, we demonstrate that a coarse-grained molecular model of the nucleosome can reproduce key aspects of nucleosome unwrapping...
September 28, 2016: ACS Central Science
Tanja Krainz, Michael M Gaschler, Chaemin Lim, Joshua R Sacher, Brent R Stockwell, Peter Wipf
Discovering compounds and mechanisms for inhibiting ferroptosis, a form of regulated, nonapoptotic cell death, has been of great interest in recent years. In this study, we demonstrate the ability of XJB-5-131, JP4-039, and other nitroxide-based lipid peroxidation mitigators to prevent ferroptotic cell death in HT-1080, BJeLR, and panc-1 cells. Several analogues of the reactive oxygen species (ROS) scavengers XJB-5-131 and JP4-039 were synthesized to probe structure-activity relationships and the influence of subcellular localization on the potency of these novel ferroptosis suppressors...
September 28, 2016: ACS Central Science
D Matthew Peacock, Casey B Roos, John F Hartwig
We report a new class of catalytic reaction: the thermal substitution of a secondary and or tertiary alkyl halide with a nitrogen nucleophile. The alkylation of a nitrogen nucleophile with an alkyl halide is a classical method for the construction of C-N bonds, but traditional substitution reactions are challenging to achieve with a secondary and or tertiary alkyl electrophile due to competing elimination reactions. A catalytic process could address this limitation, but thermal, catalytic coupling of alkyl halides with a nitrogen nucleophile and any type of catalytic coupling of an unactivated tertiary alkyl halide with a nitrogen nucleophile are unknown...
September 28, 2016: ACS Central Science
Peng Dai, Chi Zhang, Matthew Welborn, James J Shepherd, Tianyu Zhu, Troy Van Voorhis, Bradley L Pentelute
Highly efficient and selective chemical reactions are desired. For small molecule chemistry, the reaction rate can be varied by changing the concentration, temperature, and solvent used. In contrast for large biomolecules, the reaction rate is difficult to modify by adjusting these variables because stringent biocompatible reaction conditions are required. Here we show that adding salts can change the rate constant over 4 orders of magnitude for an arylation bioconjugation reaction between a cysteine residue within a four-residue sequence (π-clamp) and a perfluoroaryl electrophile...
September 28, 2016: ACS Central Science
Eun Sil Jang, Jeremy M John, Richard R Schrock
Cis,syndiotacticA-alt-B copolymers, where A and B are two enantiomerically pure trans-2,3-disubstituted-5,6-norbornenes with "opposite" chiralities, can be prepared with stereogenic-at-metal initiators of the type M(NR)(CHR')(OR")(pyrrolide). Formation of a high percentage of alternating AB copolymer linkages relies on an inversion of chirality at the metal with each propagating step and a relatively fast formation of an AB sequence as a consequence of a preferred diastereomeric relationship between the chirality at the metal and the chirality of the monomer...
September 28, 2016: ACS Central Science
Jian Yang, Azadeh Bahreman, Geert Daudey, Jeroen Bussmann, René C L Olsthoorn, Alexander Kros
Efficient delivery of drugs to living cells is still a major challenge. Currently, most methods rely on the endocytotic pathway resulting in low delivery efficiency due to limited endosomal escape and/or degradation in lysosomes. Here, we report a new method for direct drug delivery into the cytosol of live cells in vitro and invivo utilizing targeted membrane fusion between liposomes and live cells. A pair of complementary coiled-coil lipopeptides was embedded in the lipid bilayer of liposomes and cell membranes respectively, resulting in targeted membrane fusion with concomitant release of liposome encapsulated cargo including fluorescent dyes and the cytotoxic drug doxorubicin...
September 28, 2016: ACS Central Science
Joshua Lequieu, Andrés Córdoba, Daniel Hinckley, Juan J de Pablo
The self-assembly of DNA-conjugated nanoparticles represents a promising avenue toward the design of engineered hierarchical materials. By using DNA to encode nanoscale interactions, macroscale crystals can be formed with mechanical properties that can, at least in principle, be tuned. Here we present in silico evidence that the mechanical response of these assemblies can indeed be controlled, and that subtle modifications of the linking DNA sequences can change the Young's modulus from 97 kPa to 2.1 MPa. We rely on a detailed molecular model to quantify the energetics of DNA-nanoparticle assembly and demonstrate that the mechanical response is governed by entropic, rather than enthalpic, contributions and that the response of the entire network can be estimated from the elastic properties of an individual nanoparticle...
September 28, 2016: ACS Central Science
Xing Jiang, Hai-Bao Duan, Saeed I Khan, Miguel A Garcia-Garibay
Artificial molecular machines are expected to operate under conditions of very low Reynolds numbers with inertial forces orders of magnitude smaller than viscous forces. While these conditions are relatively well understood in bulk fluids, opportunities to assess the role of viscous forces in confined crystalline media are rare. Here we report one such example of diffusion-controlled rotation in crystals and its application as a probe for viscosity of MOF-confined solvent. We describe the preparation and characterization of three pillared paddlewheel MOFs, with 9,10-bis(4-pyridylethynyl)triptycene 3 as a pillar and molecular rotator, and three axially substituted dicarboxylate linkers with different lengths and steric bulk...
September 28, 2016: ACS Central Science
Seung-Ju Cho, So-Yeon Kim, Soon-Jung Park, Naree Song, Haw-Young Kwon, Nam-Young Kang, Sung-Hwan Moon, Young-Tae Chang, Hyuk-Jin Cha
Pluripotent stem cells (PSC) are promising resources for regeneration therapy, but teratoma formation is one of the critical problems for safe clinical application. After differentiation, the precise detection and subsequent elimination of undifferentiated PSC is essential for teratoma-free stem cell therapy, but a practical procedure is yet to be developed. CDy1, a PSC specific fluorescent probe, was investigated for the generation of reactive oxygen species (ROS) and demonstrated to induce selective death of PSC upon visible light irradiation...
September 28, 2016: ACS Central Science
Maxwell J Robb, Wenle Li, Ryan C R Gergely, Christopher C Matthews, Scott R White, Nancy R Sottos, Jeffrey S Moore
Microscopic damage inevitably leads to failure in polymers and composite materials, but it is difficult to detect without the aid of specialized equipment. The ability to enhance the detection of small-scale damage prior to catastrophic material failure is important for improving the safety and reliability of critical engineering components, while simultaneously reducing life cycle costs associated with regular maintenance and inspection. Here, we demonstrate a simple, robust, and sensitive fluorescence-based approach for autonomous detection of damage in polymeric materials and composites enabled by aggregation-induced emission (AIE)...
September 28, 2016: ACS Central Science
Joseph M DeSimone, Sue J Mecham, Crista L Farrell
This article was written to shed light on a series of what some have stated are not so obvious connections that link polymer synthesis in supercritical CO2 to cancer treatment and vaccines, nonflammable polymer electrolytes for lithium ion batteries, and 3D printing. In telling this story, we also attempt to show the value of versatility in applying one's primary area of expertise to address pertinent questions in science and in society. In this Outlook, we attempted to identify key factors to enable a versatile and nimble research effort to take shape in an effort to influence diverse fields and have a tangible impact in the private sector through the translation of discoveries into the marketplace...
September 28, 2016: ACS Central Science
Qing Xu, Sasanka Dalapati, Donglin Jiang
No abstract text is available yet for this article.
September 28, 2016: ACS Central Science
Andrew J Spakowitz
No abstract text is available yet for this article.
September 28, 2016: ACS Central Science
Prachi Patel
No abstract text is available yet for this article.
September 28, 2016: ACS Central Science
Katherine Bourzac
No abstract text is available yet for this article.
September 28, 2016: ACS Central Science
Dongyuan Zhao
No abstract text is available yet for this article.
September 28, 2016: ACS Central Science
Victor Mougel, Ka-Wing Chan, Georges Siddiqi, Kento Kawakita, Haruki Nagae, Hayato Tsurugi, Kazushi Mashima, Olga Safonova, Christophe Copéret
Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts...
August 24, 2016: ACS Central Science
M Safari, C Y Kwok, L F Nazar
A comprehensive experimental and theoretical analysis of the isothermal transport of species for the two model ternary-electrolytes with LiTFSI-Li2S4/dioxolane (DOL)-dimethoxyethane (DME) and LiTFSI-Li2S6/DOL-DME formulations is presented. An unambiguous picture of the polysulfide's mobility is set forth after a detailed investigation of the macroscopic transference number and diffusion coefficients. The new findings of incongruent diffusion for Li2S4 species and high significance of cross-term diffusion coefficients reformulate a fledgling view of the prevalent redox-shuttle phenomena...
August 24, 2016: ACS Central Science
Rachel C Botham, Howard S Roth, Alison P Book, Patrick J Roady, Timothy M Fan, Paul J Hergenrother
Conventional chemotherapeutics remain essential treatments for most cancers, but their combination with other anticancer drugs (including targeted therapeutics) is often complicated by unpredictable synergies and multiplicative toxicities. As cytotoxic anticancer chemotherapeutics generally function through induction of apoptosis, we hypothesized that a molecularly targeted small molecule capable of facilitating a central and defining step in the apoptotic cascade, the activation of procaspase-3 to caspase-3, would broadly and predictably enhance activity of cytotoxic drugs...
August 24, 2016: ACS Central Science
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