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  • 1
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    Use of a scaffold peptide in the biosynthesis of amino acid-derived natural products (2019)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2019
    Description: 〈p〉Genome sequencing of environmental bacteria allows identification of biosynthetic gene clusters encoding unusual combinations of enzymes that produce unknown natural products. We identified a pathway in which a ribosomally synthesized small peptide serves as a scaffold for nonribosomal peptide extension and chemical modification. Amino acids are transferred to the carboxyl terminus of the peptide through adenosine triphosphate and amino acyl-tRNA–dependent chemistry that is independent of the ribosome. Oxidative rearrangement, carboxymethylation, and proteolysis of a terminal cysteine yields an amino acid–derived small molecule. Microcrystal electron diffraction demonstrates that the resulting product is isosteric to glutamate. We show that a similar peptide extension is used during the biosynthesis of the ammosamides, which are cytotoxic pyrroloquinoline alkaloids. These results suggest an alternative paradigm for biosynthesis of amino acid–derived natural products.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Enhanced formation of aerobic granular sludge with yellow earth as nucleating agent in a sequencing batch reactor (2016)
    Institute of Physics (IOP)
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    Publication Date: 2016-09-03
    Description: Enhanced formation of aerobic granulation was investigated by adding yellow earth as a nucleating agent in a sequencing batch reactor with a constant setting time of 10 min. As a result, granules with an average diameter over 1 mm were obtained on the 4th day. The mature granules behaved better than the seed sludge in the water content, specific gravity, sludge volume index, settling velocity, and specific oxygen uptake rate. The yellow earth stimulated the secretion of extracellular polymeric substances, especially proteins. Both chemical oxygen demand and ammonia nitrogen had a removal rate over 90%, and more than 80% of the total inorganic nitrogen was removed even under aeration conditions due to simultaneous denitrification. The enhancement effects of the yellow earth might be based on the unique physicochemical characteristics and short settling time. A settling time of 10 min or more turned out not to be a prerequisite for a rapid granulation process.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 3
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    The distribution characteristics of polycyclic aromatic hydrocarbons in typical water system of North China (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-09-01
    Description: The temporal and spatial distribution of PAHs in surface-water from the typical rivers of North China was investigated. PAHs in typical rivers ranged from n.d. to 1.98 ng/L. LMW PAHs (2 and 3-ring) were abundant in surface water with high detection frequencies in Beisanhe River, while HMW PAHs (4 and 6-ring) were abundant in Luanhe River. Specific PAHs with its ratios were measured in order to deduce the possible sources of PAHs contaminant. The results indicate that the PAHs were from combustion processes in Beisanhe River, while PAHs were from petroleum products in Luanhe River.
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 4
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    Preliminary investigation on the occurrence of several sulfonamide antibiotics in the Haihe River Basin of China (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-09-01
    Description: Several samples collected from lakes, rivers and reservoirs in Haihe river basin of China were analyzed for 8 sulfonamide antibiotics by using solid-phase extraction and liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). All water samples were enriched with HLB extraction cartridges. The antibiotics were separated by gradient elution with methanol as the mobile phase adding 0.1% formic acid. The eluate was then analyzed by the mode of multiple reaction monitoring (MRM). The limits of detection (LOD) and quantification (LOQ) were 0.4-1.0 ng/L and 1.0-3.0 ng/L respectively. The method was used for the analysis of 13 samples from Haihe river basin in China. The results showed that sulfamethoxazole was present in all water samples with maximum concentration of 107.59 ng/L. Sulfadiazine was also frequently detected, concentrations ranging from 2.81 ng/L to 85.35 ng/L. Other sulfonamide antibiotics were not detected in most water samples, especially for those samples fr...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 5
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    Contribution of biomimetic collagen-ligand interaction to intrafibrillar mineralization (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Contemporary models of intrafibrillar mineralization mechanisms are established using collagen fibrils as templates without considering the contribution from collagen-bound apatite nucleation inhibitors. However, collagen matrices destined for mineralization in vertebrates contain bound matrix proteins for intrafibrillar mineralization. Negatively charged, high–molecular weight polycarboxylic acid is cross-linked to reconstituted collagen to create a model for examining the contribution of collagen-ligand interaction to intrafibrillar mineralization. Cryogenic electron microscopy and molecular dynamics simulation show that, after cross-linking to collagen, the bound polyelectrolyte caches prenucleation cluster singlets into chain-like aggregates along the fibrillar surface to increase the pool of mineralization precursors available for intrafibrillar mineralization. Higher-quality mineralized scaffolds with better biomechanical properties are achieved compared with mineralization of unmodified scaffolds in polyelectrolyte-stabilized mineralization solution. Collagen-ligand interaction provides insights on the genesis of heterogeneously mineralized tissues and the potential causes of ectopic calcification in nonmineralized body tissues.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Intrinsic magnetic topological insulators in van der Waals layered MnBi2Te4-family materials (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉The interplay of magnetism and topology is a key research subject in condensed matter physics, which offers great opportunities to explore emerging new physics, such as the quantum anomalous Hall (QAH) effect, axion electrodynamics, and Majorana fermions. However, these exotic physical effects have rarely been realized experimentally because of the lack of suitable working materials. Here, we predict a series of van der Waals layered MnBi〈sub〉2〈/sub〉Te〈sub〉4〈/sub〉-related materials that show intralayer ferromagnetic and interlayer antiferromagnetic exchange interactions. We find extremely rich topological quantum states with outstanding characteristics in MnBi〈sub〉2〈/sub〉Te〈sub〉4〈/sub〉, including an antiferromagnetic topological insulator with the long-sought topological axion states on the surface, a type II magnetic Weyl semimetal with one pair of Weyl points, as well as a collection of intrinsic axion insulators and QAH insulators in even- and odd-layer films, respectively. These notable predictions, if proven experimentally, could profoundly change future research and technology of topological quantum physics.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Numerical investigation of the effects of splitter blades on the cavitation performance of a centrifugal pump (2014)
    Institute of Physics (IOP)
    Details
    Publication Date: 2014-12-11
    Description: For the centrifugal pump, additional splitter blades are sometimes necessary in order to improve the head and efficiency. On the other hand, the additional splitter blades will have effect on the cavitation performance due to the changes at the impeller inlet channel. In order to investigate this influence, three impeller schemes were proposed based on a model pump IS50-32-160, one without splitter blades and another two with splitter blades of different inlet diameters. Numerical simulations were carried out to investigate the characteristics of internal flow and the pump cavitation performances at different NPSHA with the CFD technique. The results show that the additional splitter blades will have some positive effect on the pump cavitation performance if the inlet diameter of the splitter blade is properly selected. The reason behind such improvement is that it helps to avoid the flow blocking at the impeller inlet and the vortex cavitation inside the blade passages e...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics (IOP)
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  • 8
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    Research on the response of the water sources to the climatic change in Shiyang River Basin (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-09-01
    Description: The influence of the future climate change to the water resource will directly pose some impact on the watershed management planning and administrative strategies of Shiyang River Basin. With the purpose of exploring the influence of climate change to the runoff, this paper set Shiyang River as the study area and then established a SWAT basin hydrological model based on the data such as DEM, land use, soil, climate hydrology and so on. Besides, algorithm of SUFI2 embedded in SWAT-CUP software is adopted. The conclusion shows that SWAT Model can simulate the runoff process of Nanying River well. During the period of model verification and simulation, the runoff Nash-Sutcliffe efficient coefficient of the verification and simulation is 0.76 and 0.72 separately. The relative error between the simulation and actual measurement and the model efficient coefficient are both within the scope of acceptance, which means that the SWAT hydrological model can be properly applied into the run...
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
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  • 9
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    Effects of glass fiber modified with calcium silicate hydrate (C-S-H(I)) reinforced cement (2017)
    Institute of Physics (IOP)
    Details
    Publication Date: 2017-03-11
    Description: In this paper, calcium silicate hydrate (C-S-H(I)) and glass fiber modified with C-S-H(I) (SiF) at ambient temperature were synthesized. SiF and untreated fiber (OF) were incorporated into cement paste. Phase composition of C-S-H(I), SiF and OF was characterized by XRD. The surface morphologies were characterized by SEM. Flexural performance of fiber reinforced cement (FRC) at different curing ages was investigated. Results indicated that both SiF and OF could reinforce cement paste. SiF had a more positive effect on improving the flexural performance of FRC than OF. The strength of SiF reinforced cement was 11.48MPa after 28 days curing when fiber volume was 1.0%, 12.55% higher than that of OF reinforced cement. The flexural strength increased with the addition of fiber volume. However, the large dosage of fiber might cause a decrease in flexural strength of FRC.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 10
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    Ideal Weyl points and helicoid surface states in artificial photonic crystal structures (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-03-06
    Description: Weyl points are the crossings of linearly dispersing energy bands of three-dimensional crystals, providing the opportunity to explore a variety of intriguing phenomena such as topologically protected surface states and chiral anomalies. However, the lack of an ideal Weyl system in which the Weyl points all exist at the same energy and are separated from any other bands poses a serious limitation to the further development of Weyl physics and potential applications. By experimentally characterizing a microwave photonic crystal of saddle-shaped metallic coils, we observed ideal Weyl points that are related to each other through symmetry operations. Topological surface states exhibiting helicoidal structure have also been demonstrated. Our system provides a photonic platform for exploring ideal Weyl systems and developing possible topological devices.
    Keywords: Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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