Production of Hexanoic Acid from Long Chain Fatty Acid in Escherichia coli

Department of Biomedical EngineeringAll over the world, the efforts are under way to find the petroleum replacement resources in order to overcome fossil fuel depletion and to reduce greenhouse-gas emissions. In this respect, replacing petrochemicals with renewable alternatives is one of the principal challenges of our day. Hexanoic acid could be widely used as a precursor to biofuels and for the production of chain based chemicals such as adipic acid, hexane, amino-caproic acid and so on. In order to produce specific carbon chain fatty acid, Escherichia coli ??-oxidation pathway was engineered. First, fadE and fadR genes were deleted. And then, E. coli acyl-CoA dehydrogenase (FadE) was replaced with acyl-CoA oxidase 2 encoded by POX2 gene from Yarrowia lipolytica, which has substrate specificity towards medium to long chain fatty acyl-CoA. Finally the thioesterase??? (TesB) was overexpressed in the cell. In this study, a maximum of 210mg/L of hexanoic acid was produced by the engineered strain (MGREBA2) from 1g/L of oleic acid in 48hours of biotransformation. Based on these results, it is suggested that various oil as feedstock will be directly applied for the production of short chain fatty acids, especially hexanoic acid.ope

CD82/KAI1 Maintains the Dormancy of Long-Term Hematopoietic Stem Cells through Interaction with DARC- Expressing Macrophages

Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we examine the role of CD82/ KAI1 in niche-mediated LT-HSC maintenance. We found that CD82/ KAI1 is expressed predominantly on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs). In Cd82 +/-/+/- mice, LTHSCs were selectively lost as they exited from quiescence and differentiated. Mechanistically, CD82based TGF-b1/ Smad3 signaling leads to induction of CDK inhibitors and cell-cycle inhibition. The CD82 binding partner DARC/ CD234 is expressed on macrophages and stabilizes CD82 on LT-HSCs, promoting their quiescence. When DARC + BMmacrophages were ablated, the level of surface CD82 on LT-HSCs decreased, leading to cell-cycle entry, proliferation, and differentiation. A similar interaction appears to be relevant for human HSPCs. Thus, CD82 is a functional surface marker of LT-HSCs that maintains quiescence through interaction with DARC-expressing macrophages in the BM stem cell niche.113525Ysciescopu

Increased Transforming Growth Factor-beta1 in Alcohol Dependence

Ethanol and its metabolite acetaldehyde increase transforming growth factor beta1 (TGF-β1) expression in animal studies. TGF-β1 is related with the hepatic stellate cell (the key element of hepatic fibrogenesis) and the radial glia (the key element of neuronal migration). Blood samples were collected from 41 patients with alcohol dependence, TGF-β1 levels measured by ELISA were compared with 41 normal subjects. Plasma TGF-β1 levels in the patients with alcohol dependence (1,653.11±532.45 pg/mL) were significantly higher than those of healthy subjects (669.87±366.53 pg/mL) (P=0.000). Patients with or without liver pathology showed no difference in TGF-β1 (P=0.36). Increased TGF-β1 may mediate deleterious effect of alcohol such as hepatic fibrosis and suppressed neuronal developments in alcohol dependence patients

Combining Next-Generation Sequencing Strategies for Rapid Molecular Resource Development from an Invasive Aphid Species, Aphis glycines

Aphids are one of the most important insect taxa in terms of ecology, evolutionary biology, genetics and genomics, and interactions with endosymbionts. Additionally, many aphids are serious pest species of agricultural and horticultural plants. Recent genetic and genomic research has expanded molecular resources for many aphid species, including the whole genome sequencing of the pea aphid, Acrythosiphon pisum. However, the invasive soybean aphid, Aphis glycines, lacks in any significant molecular resources.Two next-generation sequencing technologies (Roche-454 and Illumina GA-II) were used in a combined approach to develop both transcriptomic and genomic resources, including expressed genes and molecular markers. Over 278 million bp were sequenced among the two methods, resulting in 19,293 transcripts and 56,688 genomic sequences. From this data set, 635 SNPs and 1,382 microsatellite markers were identified. For each sequencing method, different soybean aphid biotypes were used which revealed potential biotype specific markers. In addition, we uncovered 39,822 bp of sequence that were related to the obligatory endosymbiont, Buchnera aphidicola, as well as sequences that suggest the presence of Hamiltonella defensa, a facultative endosymbiont.Molecular resources for an invasive, non-model aphid species were generated. Additionally, the power of next-generation sequencing to uncover endosymbionts was demonstrated. The resources presented here will complement ongoing molecular studies within the Aphididae, including the pea aphid whole genome, lead to better understanding of aphid adaptation and evolution, and help provide novel targets for soybean aphid control

The tip shape dependence of the STM-induced luminescence

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Influence of the Tip Shape on Scanning Tunneling Luminescence Spectra: Implications for Nanomaterial Characterization

Scanning tunneling luminescence (STL) provides a unique opportunity to determine the optical properties of nanostructures beyond the diffraction limit. However, the relationship between the STL spectra and nanoscale tip shapes remains poorly understood because of the uncertainty regarding the nanoscale tip geometry. Here, we provide direct experimental evidence supporting a relationship between the tip shapes and resulting STL spectra. We find that asymmetric nanoscale tips generated dissimilar STL spectra in different directions by simultaneously collecting STL spectra in two opposing directions. Our experiment provides an efficient way to tune the STL spectra, which can be used to characterize the optical properties of nanomaterials.11Nsciescopu

Detecting the Tip Shape Dependence of the Plasmonic Photon Emission under STM

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Unusual Diffusion Behavior of Copper-Hexadecafluoro-Phthalocyanine Molecules on Au(111)

© 2020, The Korean Physical Society. The unusual bias-voltage dependence of copper-hexadecafluoro-phthalocyanine (F16CuPc) molecules on Au(111) was investigated by using scanning tunneling microscopy/spectroscopy (STM/STS) at low temperatures. Depending on the bias polarity, the molecules seem to cover the whole surface of Au(111) at positive bias voltages while they are apparently invisible in STM images at negative bias voltages. Here, we experimentally demonstrate that the molecular diffusivity on Au(111) varies according to the applied electric field induced between the STM tip and the Au(111) surface rather than the intrinsic molecule-substrate interaction. Such results are corroborated by STS measurements indicating that attraction/repulsion of a molecule indeed occurs under an STM tip at positive/negative bias voltages during sweeps of the bias voltage. In addition, we found that the diffusive molecules are immobilized at a temperature of 8 K at both positive and negative bias voltages due to a lack of thermal energy for diffusion11sciekc

Tunable Plasmonic Quantum Light Source with Silver Nanoclusters on a Silver Surface

Scanning tunneling luminescence (STL) can be used to investigate the optical properties of nanostructures with high spatial resolution beyond the diffraction limit of light. To get appropriate STL spectra, one needs to modify the tip repeatedly. However, such irreversible tip modification often leads to very unstable tips. Here, by using a scanning tunneling microscope (STM) tip, we demonstrate that STL spectra are tunable via silver nanocluster arrays fabricated directly on a silver surface. The silver nanoclusters are created by transferring silver atoms from the silver tip to the silver surface under STM. We found that the STL spectra were enhanced (suppressed) at higher (lower) energy on the clusters and that they showed opposite behaviors between the nanoclusters. Without relying on the irreversible tip shape modification, our findings indicate that we can tune the STL spectra simply by moving the STM tip over the nanoclusters. Our method can be used to provide a tunable light source for systematic nano-optical experiments and for nanoscale optical devices.11Nsciescopuskc

Systematic investigation of wear-induced cold welding in ultrahigh vacuum piezoelectric motors with non-metallic coatings

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