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Directed Evolution

Si Xuan She, Jie Yu, Wan Qi Tang, Yinlong Zhu, Yu Bo Chen, Jaka Sunarso, Wei Zhou, Zongping Shao
Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based eletrocatalysts (IrO2 and RuO2). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of La1-xSrxFeO3-δ (x = 0, 0.2, 0.5, 0.8, and 1) are synthesized and characterized. The OER specific activities in alkaline solution increase in the order of LaFeO3-δ (LF), La0.8Sr0.2FeO3-δ (LSF-0.2), La0.5Sr0.5FeO3-δ (LSF-0.5), SrFeO3-δ (SF) and La0...
March 16, 2018: ACS Applied Materials & Interfaces
Kun Liu, Chunlan Song, Aiwen Lei
Electrochemical oxidative cross-coupling with hydrogen evolution has become an environmentally friendly and efficient way to form new bonds. Direct electrosynthesis by anodic oxidation has been developed for the synthesis of complex molecules. However, in some cases, redox catalysts were needed to avoid over-oxidation and to achieve better reaction selectivity. Recently, the use of iodine as a mediator to achieve indirect electrochemical reactions has drawn increasing attention. This review article gives an overview of the recent development of iodine mediated electrochemical oxidative coupling reactions...
March 16, 2018: Organic & Biomolecular Chemistry
Peter L Cummins, Babu Kannappan, Jill E Gready
The ubiquitous enzyme Ribulose 1,5-bisphosphate carboxylase-oxygenase (RuBisCO) fixes atmospheric carbon dioxide within the Calvin-Benson cycle that is utilized by most photosynthetic organisms. Despite this central role, RuBisCO's efficiency surprisingly struggles, with both a very slow turnover rate to products and also impaired substrate specificity, features that have long been an enigma as it would be assumed that its efficiency was under strong evolutionary pressure. RuBisCO's substrate specificity is compromised as it catalyzes a side-fixation reaction with atmospheric oxygen; empirical kinetic results show a trend to tradeoff between relative specificity and low catalytic turnover rate...
2018: Frontiers in Plant Science
Joo Yeon Seok, Jina Yang, Sang Jin Choi, Hyun Gyu Lim, Un Jong Choi, Kyung-Jin Kim, Sunghoon Park, Tae Hyeon Yoo, Gyoo Yeol Jung
3-Hydroxypropionic acid (3-HP) is an important platform chemical, and biological production of 3-HP from glycerol as a carbon source using glycerol dehydratase (GDHt) and aldehyde dehydrogenase (ALDH) has been revealed to be effective because it involves a relatively simple metabolic pathway and exhibits higher yield and productivity than other biosynthetic pathways. Despite the successful attempts of 3-HP production from glycerol, the biological process suffers from problems arising from low activity and inactivation of the two enzymes...
March 12, 2018: Metabolic Engineering
Hemachander Subramanian, Robert A Gatenby
Due to the asymmetric nature of the nucleotides, the extant informational biomolecule, DNA, is constrained to replicate unidirectionally on a template. As a product of molecular evolution that sought to maximize replicative potential, DNA's unidirectional replication poses a mystery since symmetric bidirectional self-replicators obviously would replicate faster than unidirectional self-replicators and hence would have been evolutionarily more successful. Here we carefully examine the physico-chemical requirements for evolutionarily successful primordial self-replicators and theoretically show that at low monomer concentrations that possibly prevailed in the primordial oceans, asymmetric unidirectional self-replicators would have an evolutionary advantage over bidirectional self-replicators...
March 12, 2018: Journal of Theoretical Biology
James R Thunes, Julie A Phillippi, Thomas G Gleason, David A Vorp, Spandan Maiti
High lethality of aortic dissection necessitates accurate predictive metrics for dissection risk assessment. The not infrequent incidence of dissection at aortic diameters <5.5 cm, the current threshold guideline for surgical intervention (Nishimura et al., 2014), indicates an unmet need for improved evidence-based risk stratification metrics. Meeting this need requires a fundamental understanding of the structural mechanisms responsible for dissection evolution within the vessel wall. We present a structural model of the repeating lamellar structure of the aortic media comprised of elastic lamellae and collagen fiber networks, the primary load-bearing components of the vessel wall...
February 8, 2018: Journal of Biomechanics
Philip T M Carlsson, Thomas Zeuch
We have developed a new model utilizing our existing kinetic gas phase models to simulate experimental particle size distributions emerging in dry supersaturated H2 SO4 vapor homogeneously produced by rapid oxidation of SO2 through stabilized Criegee-Intermediates from 2-butene ozonolysis. We use a sectional method for simulating the particle dynamics. The particle treatment in the model is based on first principles and takes into account the transition from the kinetic to the diffusion-limited regime. It captures the temporal evolution of size distributions at the end of the ozonolysis experiment well, noting a slight underrepresentation of coagulation effects for larger particle sizes...
March 14, 2018: Journal of Chemical Physics
Franck Maunoury, Aurore Clément, Chizoba Nwankwo, Laurie Levy-Bachelot, Armand Abergel, Vincent Di Martino, Eric Thervet, Isabelle Durand-Zaleski
OBJECTIVE: To assess the cost-effectiveness of the elbasvir/grazoprevir (EBR/GZR) regimen in patients with genotype 1 chronic hepatitis C virus (HCV) infection with severe and end-stage renal disease compared to no treatment. DESIGN: This study uses a health economic model to estimate the cost-effectiveness of treating previously untreated and treatment experienced chronic hepatitis C patients who have severe and end stage renal disease with the elbasvir-grazoprevir regimen versus no treatment in the French context...
2018: PloS One
Da Wei Zhang, Jing Wei Li, Jia Xian Luo, Pei Man Xu, Li Cheng Wei, Dan Zhou, Wei Ming Xu, Dingsheng Yuan
It is essential to synthesize low-cost, earth-abundant bifunctional electrocatalysts&#13; for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for&#13; water electrolysis. Herein, we present a one-step sulfurization method to fabricate&#13; Ni3S2 nanowires directly grown on Ni foam (Ni3S2 NWs/Ni) as such an electrocatalyst.&#13; This synthetic strategy has several advantages including facile preparation, low cost&#13; and even can be expanded to large-scale preparation in the practical application...
March 15, 2018: Nanotechnology
Michael W Deem, Melia Elizabeth Bonomo
Clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated proteins (Cas) constitute a multi-functional, constantly evolving immune system in bacteria and archaea cells. A heritable, molecular memory is generated of phage, plasmids, or other mobile genetic elements that attempt to attack the cell. This memory is used to recognize and interfere with subsequent invasions from the same genetic elements. This versatile prokaryotic tool has also been used to advance applications in biotechnology...
March 15, 2018: Physical Biology
A M Kadykov, S S Krishtopenko, B Jouault, W Desrat, W Knap, S Ruffenach, C Consejo, J Torres, S V Morozov, N N Mikhailov, S A Dvoretskii, F Teppe
We report a direct observation of temperature-induced topological phase transition between the trivial and topological insulator states in an HgTe quantum well. By using a gated Hall bar device, we measure and represent Landau levels in fan charts at different temperatures, and we follow the temperature evolution of a peculiar pair of "zero-mode" Landau levels, which split from the edge of electronlike and holelike subbands. Their crossing at a critical magnetic field B_{c} is a characteristic of inverted band structure in the quantum well...
February 23, 2018: Physical Review Letters
Z H Zhong, R X Tang, M Zhou, X H Deng, Y Pang, W R Paterson, B L Giles, J L Burch, R B Tobert, R E Ergun, Y V Khotyaintsev, P-A Lindquist
Secondary flux ropes are suggested to play important roles in energy dissipation and particle acceleration during magnetic reconnection. However, their generation mechanism is not fully understood. In this Letter, we present the first direct evidence that a secondary flux rope was generated due to the evolution of an electron vortex, which was driven by the electron Kelvin-Helmholtz instability in an ion diffusion region as observed by the Magnetospheric Multiscale mission. The subion scale (less than the ion inertial length) flux rope was embedded within the electron vortex, which contained a secondary electron diffusion region at the trailing edge of the flux rope...
February 16, 2018: Physical Review Letters
Sulagna Patnaik, Gayatri Swain, K M Parida
Herein, a novel Cu-MoO3 /g-C3 N4 hybrid nanocomposite was successfully synthesized by a two-step strategy of one-pot pyrolysis followed by the impregnation method. The structure, phase, morphology and electronic environment of MoO3 , g-C3 N4 and Cu in the composite were determined by various characterization methods. The oxygen vacancies of MoO3 were ascertained by UV-DRS, Raman, and XPS analysis. The formation of the heterostructure was characterised by electrochemical measurements. The photocatalytic performance of the composite was investigated by the water reduction reaction and the reduction of an important inorganic pollutant, Cr(vi)...
March 15, 2018: Nanoscale
Ilaria Cavazzana, Laura Andreoli, Maarteen Limper, Franco Franceschini, Angela Tincani
PURPOSE OF REVIEW: This review focuses on new clinical aspects of antiphospholipid syndrome (APS) in the last 5 years. RECENT FINDINGS: The pathogenesis of APS is related to endothelial activation by mechanisms other than autoantibody-mediated massive coagulation. These include Toll-like receptors, the m-TORC pathway, and neutrophil activation, inducing an uncontrolled inflammatory cascade. Given these new pathogenetic hypotheses, the treatment of APS could be directed towards a fine balance between anticoagulation and immunomodulation...
March 15, 2018: Current Rheumatology Reports
Huanchen Wang, Chunfang Gu, Ronda J Rolfes, Henning J Jessen, Stephen B Shears
Inositol pyrophosphates (PP-InsPs) are 'energetic' intracellular signals that are ubiquitous in animals, plant and fungi; structural and biochemical characterization of PP-InsP metabolic enzymes provides insight into their evolution, reaction mechanisms, and regulation. Here, we describe the 2.35 Å resolution structure of the catalytic core of Siw14, a 5-PP-InsP phosphatase from Saccharomyces cerevisiae, and a member of the protein tyrosinephosphatase (PTP) superfamily. Conclusions that we derive from structural data are supported by extensive site-directed mutagenesis and kinetic analyses, thereby attributing new functional significance to several key residues...
March 14, 2018: Journal of Biological Chemistry
K Hari Krishna, Muthuvel Suresh Kumar
Eukaryotic translation initiation factor 2-alpha kinase (EIF2AK) proteins inhibit protein synthesis at translation initiation level, in response to various stress conditions, including oxidative stress, heme deficiency, osmotic shock, and heat shock. Origin and functional diversification of EIF2AK sequences remain ambiguous. Here we determine the origin and molecular evolution of EIF2AK proteins in lower eukaryotes and studied the molecular basis of divergence among sub-family sequences. Present work emphasized primitive origin of EIF2AK4 sub-family gene in lower eukaryotes of protozoan lineage...
2018: PloS One
Christopher Looze, Eric Strauss, Laith Jazrawi
Shoulder and elbow injuries have been described in baseball players as early as the 1940s. Ulnar collateral ligament (UCL) tears have been recognized as a significant source of disability for baseball players and have been seen in increasing frequency as training regimens and level of play have become more intense and rigorous. Our understanding and treatment of these injuries have also evolved over time. This article summarizes the evolution of the treatment of UCL tears and discusses future directions for the treatment and prevention of these injuries...
March 2018: Bulletin of the Hospital for Joint Diseases
James Kennedy, Mihaela Pavličev
In human females, direct or indirect stimulation of the clitoris plays a central role in reaching orgasm. A majority of women report that penetrative coitus alone is insufficient for triggering orgasm, puzzling researchers who expect orgasm to be an outcome of procreative intercourse. In the present paper, we turn our attention to the evolutionary role that such unreliability of orgasm at coitus might have played in human evolution. We emphasize that we do not thereby attempt an explanation of its origin, but its potential evolutionary effect...
March 14, 2018: Journal of Experimental Zoology. Part B, Molecular and Developmental Evolution
Hiang Kwee Lee, Charlynn Sher Lin Koh, Yih Hong Lee, Chong Liu, In Yee Phang, Xuemei Han, Chia-Kuang Tsung, Xing Yi Ling
Electrochemical nitrogen-to-ammonia fixation is emerging as a sustainable strategy to tackle the hydrogen- and energy-intensive operations by Haber-Bosch process for ammonia production. However, current electrochemical nitrogen reduction reaction (NRR) progress is impeded by overwhelming competition from the hydrogen evolution reaction (HER) across all traditional NRR catalysts and the requirement for elevated temperature/pressure. We achieve both excellent NRR selectivity (~90%) and a significant boost to Faradic efficiency by 10 percentage points even at ambient operations by coating a superhydrophobic metal-organic framework (MOF) layer over the NRR electrocatalyst...
March 2018: Science Advances
Zhaoqun Liu, Lingling Wang, Zhao Lv, Zhi Zhou, Weilin Wang, Meijia Li, Qilin Yi, Limei Qiu, Linsheng Song
It is becoming increasingly clear that neurotransmitters impose direct influence on regulation of the immune process. Recently, a simple but sophisticated neuroendocrine-immune (NEI) system was identified in oyster, which modulated neural immune response via a "nervous-hemocyte"-mediated neuroendocrine immunomodulatory axis (NIA)-like pathway. In the present study, the de novo synthesis of neurotransmitters and their immunomodulation in the hemocytes of oyster Crassostrea gigas were investigated to understand the autocrine/paracrine pathway independent of the nervous system...
2018: Frontiers in Immunology
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