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Accounts of Chemical Research

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https://www.readbyqxmd.com/read/28644617/dynamic-covalent-chemistry-of-carbon-dioxide-opportunities-to-address-environmental-issues
#1
Jean Septavaux, Geoffroy Germain, Julien Leclaire
Extraction and purification of basic chemicals from complex mixtures has been a persistent issue throughout the development of the chemical sciences. The chemical industry and academic research have grown over the centuries by following a deconstruction-reconstruction approach, reminiscent of the metabolism process. Chemists have designed and optimized extraction, purification, and transformation processes of molecules from natural deposits (fossil fuels, biomass, ores), in order to reassemble them into complex adducts...
June 23, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28644616/importance-of-a-fully-anharmonic-treatment-of-equilibrium-isotope-fractionation-properties-of-dissolved-ionic-species-as-evidenced-by-li-aq
#2
Romain Dupuis, Magali Benoit, Mark E Tuckerman, Merlin Méheut
Equilibrium fractionation of stable isotopes is critically important in fields ranging from chemistry, including medicinal chemistry, electrochemistry, geochemistry, and nuclear chemistry, to environmental science. The dearth of reliable estimates of equilibrium fractionation factors, from experiment or from natural observations, has created a need for accurate computational approaches. Because isotope fractionation is a purely quantum mechanical phenomenon, exact calculation of fractionation factors is nontrivial...
June 23, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28644007/cyclotides-as-tools-in-chemical-biology
#3
Simon J de Veer, Joachim Weidmann, David J Craik
Among the various molecules that plants produce for defense against pests and pathogens, cyclotides stand out as exceptionally stable and structurally unique. These ribosomally synthesized peptides are around 30 amino acids in size, and are stabilized by a head-to-tail cyclic peptide backbone and three disulfide bonds that form a cystine knot. They occur in certain plants of the Rubiaceae, Violaceae, Cucurbitaceae, Fabaceae, and Solanaceae families, with an individual plant producing up to hundreds of different cyclotides...
June 23, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636366/oxygenation-via-c-h-c-c-bond-activation-with-molecular-oxygen
#4
Yu-Feng Liang, Ning Jiao
The selective oxidation of organic molecules is a fundamentally important component of modern synthetic chemistry. In the past decades, direct oxidative C-H and C-C bond functionalization has proved to be one of the most efficient and straightforward methods to synthesize complex products from simple and readily available starting materials. Among these oxidative processes, the use of molecular oxygen as a green and sustainable oxidant has attracted considerable attention because of its highly atom-economical, abundant, and environmentally friendly characteristics...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636365/sustainable-elastomers-from-renewable-biomass
#5
Zhongkai Wang, Liang Yuan, Chuanbing Tang
Sustainable elastomers have undergone explosive growth in recent years, partly due to the resurgence of biobased materials prepared from renewable natural resources. However, mounting challenges still prevail: How can the chemical compositions and macromolecular architectures of sustainable polymers be controlled and broadened? How can their processability and recyclability be enabled? How can they compete with petroleum-based counterparts in both cost and performance? Molecular-biomass-derived polymers, such as polymyrcene, polymenthide, and poly(ε-decalactone), have been employed for constructing thermoplastic elastomers (TPEs)...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636313/iodine-iii-reagents-in-radical-chemistry
#6
Xi Wang, Armido Studer
The chemistry of hypervalent iodine(III) compounds has gained great interest over the past 30 years. Hypervalent iodine(III) compounds show valuable ionic reactivity due to their high electrophilicity but also express radical reactivity as single electron oxidants for carbon and heteroatom radical generation. Looking at ionic chemistry, these iodine(III) reagents can act as electrophiles to efficiently construct C-CF3, X-CF3 (X = heteroatom), C-Rf (Rf = perfluoroalkyl), X-Rf, C-N3, C-CN, S-CN, and C-X bonds...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636311/insights-into-integrated-lead-generation-and-target-identification-in-malaria-and-tuberculosis-drug-discovery
#7
John Okombo, Kelly Chibale
New, safe and effective drugs are urgently needed to treat and control malaria and tuberculosis, which affect millions of people annually. However, financial return on investment in the poor settings where these diseases are mostly prevalent is very minimal to support market-driven drug discovery and development. Moreover, the imminent loss of therapeutic lifespan of existing therapies due to evolution and spread of drug resistance further compounds the urgency to identify novel effective drugs. However, the advent of new public-private partnerships focused on tropical diseases and the recent release of large data sets by pharmaceutical companies on antimalarial and antituberculosis compounds derived from phenotypic whole cell high throughput screening have spurred renewed interest and opened new frontiers in malaria and tuberculosis drug discovery...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636310/sensing-mechanisms-in-the-redox-regulated-2fe-2s-cluster-containing-bacterial-transcriptional-factor-soxr
#8
Kazuo Kobayashi
Bacteria possess molecular biosensors that enable responses to a variety of stressful conditions, including oxidative stress, toxic compounds, and interactions with other organisms, through elaborately coordinated regulation of gene expression. In Escherichia coli and related bacteria, the transcription factor SoxR functions as a sensor of oxidative stress and nitric oxide (NO). SoxR protein contains a [2Fe-2S] cluster essential for its transcription-enhancing activity, which is regulated by redox changes in the [2Fe-2S] cluster...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28609611/selective-aliphatic-carbon-carbon-bond-activation-by-rhodium-porphyrin-complexes
#9
Ching Tat To, Kin Shing Chan
The carbon-carbon bond activation of organic molecules with transition metal complexes is an attractive transformation. These reactions form transition metal-carbon bonded intermediates, which contribute to fundamental understanding in organometallic chemistry. Alternatively, the metal-carbon bond in these intermediates can be further functionalized to construct new carbon-(hetero)atom bonds. This methodology promotes the concept that the carbon-carbon bond acts as a functional group, although carbon-carbon bonds are kinetically inert...
June 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28608673/organic-donor-acceptor-complexes-as-novel-organic-semiconductors
#10
Jing Zhang, Wei Xu, Peng Sheng, Guangyao Zhao, Daoben Zhu
Organic donor-acceptor (DA) complexes have attracted wide attention in recent decades, resulting in the rapid development of organic binary system electronics. The design and synthesis of organic DA complexes with a variety of component structures have mainly focused on metallicity (or even superconductivity), emission, or ferroelectricity studies. Further efforts have been made in high-performance electronic investigations. The chemical versatility of organic semiconductors provides DA complexes with a great number of possibilities for semiconducting applications...
June 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28605194/discovery-of-two-bacterial-nitric-oxide-responsive-proteins-and-their-roles-in-bacterial-biofilm-regulation
#11
Sajjad Hossain, Lisa-Marie Nisbett, Elizabeth M Boon
Bacterial biofilms form when bacteria adhere to a surface and produce an exopolysaccharide matrix ( Costerton Science 1999 , 284 , 1318 ; Davies Science 1998 , 280 , 295 ; Flemming Nat. Rev. Microbiol. 2010 , 8 , 623 ). Because biofilms are resistant to antibiotics, they are problematic in many aspects of human health and welfare, causing, for instance, persistent fouling of medical implants such as catheters and artificial joints ( Brunetto Chimia 2008 , 62 , 249 ). They are responsible for chronic infections in the lungs of cystic fibrosis patients and in open wounds, such as those associated with burns and diabetes...
June 12, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28598597/azapeptide-synthesis-methods-for-expanding-side-chain-diversity-for-biomedical-applications
#12
Ramesh Chingle, Caroline Proulx, William D Lubell
Mimicry of bioactive conformations is critical for peptide-based medicinal chemistry because such peptidomimetics may augment stability, enhance affinity, and increase specificity. Azapeptides are peptidomimetics in which the α-carbon(s) of one or more amino acid residues are substituted by nitrogen. The resulting semicarbazide analogues have been shown to reinforce β-turn conformation through the combination of lone pair-lone pair repulsion of the adjacent hydrazine nitrogen and urea planarity. Substitution of a semicarbazide for an amino amide residue in a peptide may retain biological activity and add benefits such as improved metabolic stability...
June 9, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28594167/toward-an-expanded-genome-structural-and-computational-characterization-of-an-artificially-expanded-genetic-information-system
#13
Nigel G J Richards, Millie M Georgiadis
Although the fundamental properties of DNA as first proposed by Watson and Crick in 1953 provided a basic understanding of how duplex DNA was organized and might be replicated, it was not until the first crystal structures of DNA (Z-DNA in 1979, B-DNA in 1980, and A-DNA in 1982) that the true complexity of the molecule began to be appreciated. Many crystal structures of oligonucleotides have since shed light on the helical forms that "Watson-Crick" DNA can adopt, their associated groove widths, and the properties of the nucleobase pairs and their interactions in all three helical forms...
June 8, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28590712/structural-characterization-of-intermetallic-compounds-by-27-al-solid-state-nmr-spectroscopy
#14
Christopher Benndorf, Hellmut Eckert, Oliver Janka
Intermetallic compounds are of broad interest for solid state chemists, condensed matter physicists, and material scientists due to their intriguing crystal chemistry, their physical properties, and their potential applications, ranging from lab curiosities to everyday objects. To characterize and understand the properties of new compounds and novel materials, the availability of structural information, particularly single-crystal X-ray diffraction data, is a mandatory prerequisite. Especially when it comes to the formation of compounds with deficient or mixed site occupancies, superstructures, or representatives crystallizing in other, thus far unknown structure types, a complementary method for structural analysis is of great value...
June 7, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28586208/measurement-and-modeling-of-setschenow-constants-for-selected-hydrophilic-compounds-in-nacl-and-cacl2-simulated-carbon-storage-brines
#15
Aniela Burant, Gregory V Lowry, Athanasios K Karamalidis
Carbon capture, utilization, and storage (CCUS), a climate change mitigation strategy, along with unconventional oil and gas extraction, generates enormous volumes of produced water containing high salt concentrations and a litany of organic compounds. Understanding the aqueous solubility of organic compounds related to these operations is important for water treatment and reuse alternatives, as well as risk assessment purposes. The well-established Setschenow equation can be used to determine the effect of salts on aqueous solubility...
June 6, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28573866/mid-infrared-laser-induced-fluorescence-with-nanosecond-time-resolution-using-a-superconducting-nanowire-single-photon-detector-new-technology-for-molecular-science
#16
Li Chen, Dirk Schwarzer, Varun B Verma, Martin J Stevens, Francesco Marsili, Richard P Mirin, Sae Woo Nam, Alec M Wodtke
In contrast to UV photomultiplier tubes that are widely used in physical chemistry, mid-infrared detectors are notorious for poor sensitivity and slow time response. This helps explain why, despite the importance of infrared spectroscopy in molecular science, mid-infrared fluorescence is not more widely used. In recent years, several new technologies have been developed that open new experimental possibilities for research in the mid-infrared. In this Account, we present one of the more promising technologies, superconducting nanowire single photon detectors (SNSPDs) by sharing our experience with its use in a typical experiment carried out by physical chemists (laser-induced fluorescence) and comparing the SNSPD to a detector commonly used by physical chemists (InSb at LN Temperature)...
June 2, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28570824/protein-epitope-mimetics-from-new-antibiotics-to-supramolecular-synthetic-vaccines
#17
Katja Zerbe, Kerstin Moehle, John A Robinson
Protein epitope mimetics provide powerful tools to study biomolecular recognition in many areas of chemical biology. They may also provide access to new biologically active molecules and potentially to new classes of drug and vaccine candidates. Here we highlight approaches for the design of folded, structurally defined epitope mimetics, by incorporating backbone and side chains of hot residues onto a stable constrained scaffold. Using robust synthetic methods, the structural, biological, and physical properties of epitope mimetics can be optimized, by variation of both side chain and backbone chemistry...
June 1, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28562014/ten-good-reasons-for-the-use-of-the-tellurium-centered-anderson-evans-polyoxotungstate-in-protein-crystallography
#18
Aleksandar Bijelic, Annette Rompel
Protein crystallography represents at present the most productive and most widely used method to obtain structural information on target proteins and protein-ligand complexes within the atomic resolution range. The knowledge obtained in this way is essential for understanding the biology, chemistry, and biochemistry of proteins and their functions but also for the development of compounds of high pharmacological and medicinal interest. Here, we address the very central problem in protein crystallography: the unpredictability of the crystallization process...
May 31, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28561588/protein-domain-mimics-as-modulators-of-protein-protein-interactions
#19
Nicholas Sawyer, Andrew M Watkins, Paramjit S Arora
Protein-protein interactions (PPIs) are ubiquitous in biological systems and often misregulated in disease. As such, specific PPI modulators are desirable to unravel complex PPI pathways and expand the number of druggable targets available for therapeutic intervention. However, the large size and relative flatness of PPI interfaces make them challenging molecular targets. This Account describes our systematic approach using secondary and tertiary protein domain mimics (PDMs) to specifically modulate PPIs. Our strategy focuses on mimicry of regular secondary and tertiary structure elements from one of the PPI partners to inspire rational PDM design...
May 31, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28561581/odd-n-cumulenes-n-3-5-7-9-synthesis-characterization-and-reactivity
#20
Dominik Wendinger, Rik R Tykwinski
In comparison to the omnipresent two- and three-dimensional allotropes of carbon, namely, graphite and diamond (as well as recent entries graphene, carbon nanotubes, and fullerenes), a detailed understanding of the one-dimensional carbon allotrope carbyne is not well established, and even the existence of carbyne has been a matter of controversy over the past decades. Composed of sp-hybridized carbon, carbyne could potentially exist in two forms, either as a polyyne (alternating single and triple bonds, expected to show a semiconducting behavior) or as a cumulene (all carbon atoms are connected via double bonds, predicted to show metallic behavior)...
May 31, 2017: Accounts of Chemical Research
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