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Accounts of Chemical Research

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https://www.readbyqxmd.com/read/28741360/influence-of-chemical-mechanical-and-transport-processes-on-wellbore-leakage-from-geologic-co2-storage-reservoirs
#1
Susan A Carroll, Jaisree Iyer, Stuart D C Walsh
Wells are considered to be high-risk pathways for fluid leakage from geologic CO2 storage reservoirs, because breaches in this engineered system have the potential to connect the reservoir to groundwater resources and the atmosphere. Given these concerns, a few studies have assessed leakage risk by evaluating regulatory records, often self-reported, documenting leakage in gas fields. Leakage is thought to be governed largely by initial well-construction quality and the method of well abandonment. The geologic carbon storage community has raised further concerns because acidic fluids in the CO2 storage reservoir, alkaline cement meant to isolate the reservoir fluids from the overlying strata, and steel casings in wells are inherently reactive systems...
July 25, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28735540/the-n%C3%A2-%C3%AF-interaction
#2
Robert W Newberry, Ronald T Raines
The carbonyl group holds a prominent position in chemistry and biology not only because it allows diverse transformations but also because it supports key intermolecular interactions, including hydrogen bonding. More recently, carbonyl groups have been found to interact with a variety of nucleophiles, including other carbonyl groups, in what we have termed an n→π* interaction. In an n→π* interaction, a nucleophile donates lone-pair (n) electron density into the empty π* orbital of a nearby carbonyl group...
July 23, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28731693/isolable-bis-triarylamine-dications-analogues-of-thiele-s-chichibabin-s-and-m%C3%A3-ller-s-hydrocarbons
#3
Gengwen Tan, Xinping Wang
Since the pioneering work by Thiele and Chichibabin, who synthesized the first diradicals bridged by phenylene and biphenylene groups in 1904 and 1907, respectively, numerous efforts have been devoted to synthesizing stable diradicals during the last few decades, and several strategies have been developed to stabilize these highly reactive diradicals. In this Account, we describe the synthesis and characterization of isolable bis(triarylamine) dications, nitrogen analogues of Thiele's, Chichibabin's, and Müller's hydrocarbons, which represent facilely accessible, stable diradicals by replacing carbinyl centers with isoelectronic aminium centers...
July 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28731691/singlet-oxygen-photophysics-in-liquid-solvents-converging-on-a-unified-picture
#4
Mikkel Bregnhøj, Michael Westberg, Boris F Minaev, Peter R Ogilby
Singlet oxygen, O2(a(1)Δg), the lowest excited electronic state of molecular oxygen, is an omnipresent part of life on earth. It is readily formed through a variety of chemical and photochemical processes, and its unique reactions are important not just as a tool in chemical syntheses but also in processes that range from polymer degradation to signaling in biological cells. For these reasons, O2(a(1)Δg) has been the subject of intense activity in a broad distribution of scientific fields for the past ∼50 years...
July 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28726382/interparticle-reactions-an-emerging-direction-in-nanomaterials-chemistry
#5
K R Krishnadas, Ananya Baksi, Atanu Ghosh, Ganapati Natarajan, Anirban Som, Thalappil Pradeep
Nanoparticles exhibit a rich variety in terms of structure, composition, and properties. However, reactions between them remain largely unexplored. In this Account, we discuss an emerging aspect of nanomaterials chemistry, namely, interparticle reactions in solution phase, similar to reactions between molecules, involving atomically precise noble metal clusters. A brief historical account of the developments, starting from the bare, gas phase clusters, which led to the synthesis of atomically precise monolayer protected clusters in solution, is presented first...
July 20, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28726381/impact-of-the-metallic-crystalline-structure-on-the-properties-of-nanocrystals-and-their-mesoscopic-assemblies
#6
Marie-Paule Pileni
The spontaneous assembly of uniform-sized globular entities into ordered arrays is a universal phenomenon observed for objects with diameters spanning a broad range of length scales. These extend from the atomic scale (10(-8) cm), through molecular and macromolecular scales with proteins, synthetic low polymers, and colloidal crystals (∼10(-6) cm), to the wavelength of visible light (∼10(-5) cm). The associated concepts of sphere packing have had an influence in diverse fields ranging from pure geometrical analysis to architectural models or ideals...
July 20, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28723107/chemical-approaches-to-investigate-labile-peptide-and-protein-phosphorylation
#7
Anett Hauser, Martin Penkert, Christian P R Hackenberger
Protein phosphorylation is by far the most abundant and most studied post-translational modification (PTM). For a long time, phosphate monoesters of serine (pSer), threonine (pThr), and tyrosine (pTyr) have been considered as the only relevant forms of phosphorylation in organisms. Recently, several research groups have dedicated their efforts to the investigation of other, less characterized phosphoamino acids as naturally occurring PTMs. Such apparent peculiar phosphorylations include the phosphoramidates of histidine (pHis), arginine (pArg), and lysine (pLys), the phosphorothioate of cysteine (pCys), and the anhydrides of pyrophosphorylated serine (ppSer) and threonine (ppThr)...
July 19, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28723098/a-new-area-in-main-group-chemistry-zerovalent-monoatomic-silicon-compounds-and-their-analogues
#8
Shenglai Yao, Yun Xiong, Matthias Driess
Monoatomic zerovalent main-group element complexes emerged very recently and attracted increasing attention of both theoretical and experimental chemists. In particular, zerovalent silicon complexes and their congeners (metallylones) stabilized by neutral Lewis donors are of significant importance not only because of their intriguing electronic structure but also because they can serve as useful building blocks for novel chemical species. Featuring four valence electrons as two lone pairs at the central atoms, such complexes may form donor-acceptor adducts with Lewis acids...
July 19, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28723063/using-cooperatively-folded-peptides-to-measure-interaction-energies-and-conformational-propensities
#9
Maziar S Ardejani, Evan T Powers, Jeffery W Kelly
The rates and equilibria of the folding of biopolymers are determined by the conformational preferences of the subunits that make up the sequence of the biopolymer and by the interactions that are formed in the folded state in aqueous solution. Because of the centrality of these processes to life, quantifying conformational propensities and interaction strengths is vitally important to understanding biology. In this Account, we describe our use of peptide model systems that fold cooperatively yet are small enough to be chemically synthesized to measure such quantities...
July 19, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28719188/phage-selection-of-cyclic-peptides-for-application-in-research-and-drug-development
#10
Kaycie Deyle, Xu-Dong Kong, Christian Heinis
Cyclic peptides can bind to protein targets with high affinities and selectivities, which makes them an attractive modality for the development of research reagents and therapeutics. Additional properties, including low inherent toxicity, efficient chemical synthesis, and facile modification with labels or immobilization reagents, increase their attractiveness. Cyclic peptide ligands against a wide range of protein targets have been isolated from natural sources such as bacteria, fungi, plants, and animals...
July 18, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28715203/a-bioinorganic-approach-to-fragment-based-drug-discovery-targeting-metalloenzymes
#11
Seth M Cohen
Metal-dependent enzymes (i.e., metalloenzymes) make up a large fraction of all enzymes and are critically important in a wide range of biological processes, including DNA modification, protein homeostasis, antibiotic resistance, and many others. Consequently, metalloenzymes represent a vast and largely untapped space for drug development. The discovery of effective therapeutics that target metalloenzymes lies squarely at the interface of bioinorganic and medicinal chemistry and requires expertise, methods, and strategies from both fields to mount an effective campaign...
July 17, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28715199/jumping-hurdles-peptides-able-to-overcome-biological-barriers
#12
Macarena Sánchez-Navarro, Meritxell Teixidó, Ernest Giralt
The cell membrane, the gastrointestinal tract, and the blood-brain barrier (BBB) are good examples of biological barriers that define and protect cells and organs. They impose different levels of restriction, but they also share common features. For instance, they all display a high lipophilic character. For this reason, hydrophilic compounds, like peptides, proteins, or nucleic acids have long been considered as unable to bypass them. However, the discovery of cell-penetrating peptides (CPPs) opened a vast field of research...
July 17, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28704031/supported-dendrimer-encapsulated-metal-clusters-toward-heterogenizing-homogeneous-catalysts
#13
Rong Ye, Aleksandr V Zhukhovitskiy, Christophe V Deraedt, F Dean Toste, Gabor A Somorjai
Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles-some without homogeneous analogues-for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed...
July 13, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28700203/mechanisms-of-atmospherically-relevant-cluster-growth
#14
Bryan R Bzdek, Joseph W DePalma, Murray V Johnston
Atmospheric aerosols impact global climate either directly by scattering solar radiation or indirectly by serving as cloud condensation nuclei, which influence cloud albedo and precipitation patterns. Our scientific understanding of these impacts is poor relative to that of, for instance, greenhouse gases, in part because it is difficult to predict particle number concentrations. One important pathway by which particles are added to the atmosphere is new particle formation, where gas phase precursors form molecular clusters that subsequently grow to the climatically relevant size range (50-100 nm diameter)...
July 12, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28696097/chemical-reactions-of-molecules-promoted-and-simultaneously-imaged-by-the-electron-beam-in-transmission-electron-microscopy
#15
Stephen T Skowron, Thomas W Chamberlain, Johannes Biskupek, Ute Kaiser, Elena Besley, Andrei N Khlobystov
The main objective of this Account is to assess the challenges of transmission electron microscopy (TEM) of molecules, based on over 15 years of our work in this field, and to outline the opportunities in studying chemical reactions under the electron beam (e-beam). During TEM imaging of an individual molecule adsorbed on an atomically thin substrate, such as graphene or a carbon nanotube, the e-beam transfers kinetic energy to atoms of the molecule, displacing them from equilibrium positions. Impact of the e-beam triggers bond dissociation and various chemical reactions which can be imaged concurrently with their activation by the e-beam and can be presented as stop-frame movies...
July 11, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28692282/design-and-applications-of-metastable-state-photoacids
#16
Yi Liao
Proton transfer is one of the most common processes in nature, and many chemical, material, and biological processes are sensitive to proton concentration, from acid-catalyzed reactions to the activities of many enzymes. Photoacids that reversibly undergo proton dissociation upon irradiation promise remote spatial and temporal control over proton-sensitive processes and could provide a way to convert photoenergy into other types of energy. The recently discovered metastable-state photoacids can produce a large proton concentration with high efficiency and good reversibility...
July 10, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28692276/cooperativity-scale-a-structure-mechanism-correlation-in-the-self-assembly-of-benzene-1-3-5-tricarboxamides
#17
Chidambar Kulkarni, E W Meijer, Anja R A Palmans
The self-assembly of small and well-defined molecules using noncovalent interactions to generate various nano- and microarchitectures has been extensively studied. Among various architectures, one-dimensional (1-D) nano-objects have garnered significant attention. It has become increasingly evident that a cooperative or nucleation-elongation mechanism of polymerization leads to highly ordered 1-D supramolecular polymers, analogous to shape-persistent biopolymers such as actin. With this in mind, achieving cooperativity in self-assembled structures has been actively pursued with significant success...
July 10, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28686419/factors-determining-the-rate-and-selectivity-of-4e-4h-electrocatalytic-reduction-of-dioxygen-by-iron-porphyrin-complexes
#18
Sudipta Chatterjee, Kushal Sengupta, Biswajit Mondal, Subal Dey, Abhishek Dey
Reactivity as well as selectivity are crucial in the activation and electrocatalytic reduction of molecular oxygen. Recent developments in the understanding of the mechanism of electrocatalytic O2 reduction by iron porphyrin complexes in situ using surface enhanced resonance Raman spectroscopy coupled to rotating disc electrochemistry (SERRS-RDE) in conjunction with H/D isotope effects on electrocatalytic current reveals that the rate of O2 reduction, ∼10(4) to 10(5) M(-1) s(-1) for simple iron porphyrins, is limited by the rate of O-O bond cleavage of an intermediate ferric peroxide species (Fe(III)-OOH)...
July 7, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28686035/nanoscale-chemical-processes-affecting-storage-capacities-and-seals-during-geologic-co2-sequestration
#19
Young-Shin Jun, Lijie Zhang, Yujia Min, Qingyun Li
Geologic CO2 sequestration (GCS) is a promising strategy to mitigate anthropogenic CO2 emission to the atmosphere. Suitable geologic storage sites should have a porous reservoir rock zone where injected CO2 can displace brine and be stored in pores, and an impermeable zone on top of reservoir rocks to hinder upward movement of buoyant CO2. The injection wells (steel casings encased in concrete) pass through these geologic zones and lead CO2 to the desired zones. In subsurface environments, CO2 is reactive as both a supercritical (sc) phase and aqueous (aq) species...
July 7, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28682627/ribosomal-natural-products-tailored-to-fit
#20
Michael A Funk, Wilfred A van der Donk
Ribosomally synthesized and Post-translationally modified Peptides (RiPPs) take advantage of the ribosomal translation machinery to generate linear peptides that are subsequently modified with heterocycles and/or macrocycles to impose three-dimensional structure and thwart degradation by proteases. Although RiPP precursors are limited to proteinogenic amino acids, post-translational modifications (PTMs) can alter the structure of individual amino acids and thereby improve the stability and biological activity of the molecule...
July 6, 2017: Accounts of Chemical Research
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