Engineering topics
Li, Jiang
Publications and source records attributed to Li, Jiang.
Programming PAM antennae for efficient CRISPR-Cas9 DNA editing
Bacterial CRISPR-Cas9 nucleases have been repurposed as powerful genome editing tools. Whereas engineering guide RNAs or Cas nucleases have proven to improve the efficiency of CRISPR editing, modulation of protospacer-adjacent motif (PAM), indispensable for CRISPR, has been less explored. Here, we develop a DNA origami–based platform to program a PAM antenna microenvironment and address its performance at the single-molecule level with submolecular resolution. To mimic spatially controlled in vivo PAM distribution as may occur in chromatin, we investigate the effect of PAM antennae surrounding target DNA. We find that PAM antennae effectively sensitize the DNA cleavage by recruiting Cas9 molecules. Super-resolution tracking of single single-guide RNA/Cas9s reveals localized translocation of Cas9 among spatially proximal PAMs. We find that the introduction of the PAM antennae effectively modulates the microenvironment for enhanced target cleavage (up to ~50%). These results provide insight into factors that promote more efficient genome editing.
DFT simulation of the X-ray diffraction pattern of aluminum-ion-intercalated graphite used as the cathode material of the aluminum-ion battery
Many breakthroughs have been achieved in rechargeable aluminum-ion battery technologies in recent years. Most recently, operando X-ray diffraction (XRD) combined with density functional theory (DFT) calculations was reported to study the chloroaluminate anion (AlCl 4 -)-intercalated graphite cathode of the battery. However, there are quite a few discrepancies between the measured and simulated XRD patterns. This work is focused on the simulation of XRD patterns of graphite intercalation compounds (GICs) with DFT calculations. Our results reveal that both the geometry of AlCl 4 - in graphite and the gallery height of GICs are dependent on the intercalant density. At low intercalant density, the gallery height keeps constant, but at high intercalant densities, the gallery height is linearly related to the intercalant density. Our simulated XRD patterns are highly consistent with the measured operando XRD patterns. Not only do the angles of the peaks match very well, but also the relative intensities and the corresponding electrode capacities show reasonable agreement with the experimental results. The DFT simulation of the XRD pattern provides significant information on the stage index and the charge capacity of the GIC electrode.
An unconventional DCOx favored Co/N-C catalyst for efficient conversion of fatty acids and esters to liquid alkanes
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Chemoselective Hydrodeoxygenation of Carboxylic Acids to Hydrocarbons over Nitrogen-doped Carbon-Alumina Hybrid-Supported Iron Catalysts
Here, the establishment of catalyst systems for chemoselective hydrodeoxygenation (HDO) of carboxylic acids to hydrocarbons, such as the HDO of long-chain fatty acids to alkanes, is important for biomass-to-biofuel conversion. As the most abundant and probably the cheapest transition-metal on the earth, iron is a promising non-noble alternative to precious metals for large-scale conversion of biomass. However, it usually suffers from unsatisfactory activity. In this work, nitrogen-doped carbon-alumina hybrid-supported iron (Fe-N-C@Al 2 O 3 ) catalyst is established for chemoselective HDO of carboxylic acids to hydrocarbons. By using stearic acid HDO as the model reaction, n-octadecane and n-hepadecane are produced with yields of 91.9% and 6.0%, respectively. Triglycerides can also be converted into liquid alkanes with total molar yield of >92%. In addition, the iron catalyst can chemoselectively catalyze the HDO of carboxylic acid group in the presence of other functional groups such as an aromatic ring. This chemoselectivity is rarely seen before because the aromatic ring is usually easier to be hydrogenated than carrying out HDO of carboxylic acid group. The characterization results showed that both the formation of nitrogen-doped carbon-alumina hybrid and the iron-loading are important for the Lewis basicity of these catalysts, in order to adsorb the acid substrates. The addition of melamine as nitrogen precursor during pyrolysis eliminates undesired reactions between iron precursor and alumina support to form inactive hercynite phase, leading to the formation of Fe 3 C active phase for the hydrogenation of –COOH to –CH 2 OH and the hybrid of N-C and alumina for the HDO of -CH 2 OH to –CH 3 .
Achieving Grain Refinement and Related Mechanical Property Improvement of an Al-Zn-Mg-Cu Alloy Through Severe Plastic Deformation
Microstructural features and mechanical properties of an Al-Zn-Mg-Cu alloy processed by equal-channel angular pressing (ECAP) have been investigated. The equivalent plastic strain obtained from the simulation agrees well with that from the analytical calculation in a way that both increase with an increase in deformation, but the strain distribution is non-uniform, appearing as a strain gradient along the norm direction. Microstructure investigation shows that grain refinement is achieved in frequency of low-angle grain boundaries fabricated by ECAP. The pole density is reduced by ECAP, during which the Brass and Goss type textures are introduced. TEM results show chain-like recrystallized grains formed at the grain boundaries and broken second-phase particles come into being due to the heavy shear force. After ECAP, the hardness and strength increase significantly while the elongation is reduced. Besides, an extreme strengthening is confirmed because of the balance between dynamic hardening and softening. The microstructure evolution mechanism is revealed in terms of grain refinement, precipitate phase breakage and texture evolution.
Characterization of a thermostable κ‐carrageenase from a hot spring bacterium and plant protection activity of the oligosaccharide enzymolysis product
Abstract Background Seaweed oligosaccharides are environmentally‐friendly natural products and their use for disease control in sustainable agriculture is extremely promising. Enzymatic digestion to prepare seaweed oligosaccharides has drawn considerable interest. However, the study of enzymatically degraded products of carrageenan is still in its infancy compared with that of other hydrocolloids such as agar and alginate. To prepare degraded carrageenan on a commercial scale, it is necessary to select superior producer bacterial strains to improve the yield and thermostability of carrageenases. Results The carrageenan‐degrading bacterium Bacillus sp. HT19 was isolated from sediment of a hot spring in Indonesia, and a κ‐carrageenase with high activity was purified from the culture supernatant. The purified enzyme, named Car19, had maximum activity (538 U mg −1 ) at 60 °C and pH 7.0. Notably, the enzyme retained >90% of its initial activity after incubation at 60 °C for 24 h. The Ca 2+ obviously improved the thermostability of Car19 at 70 °C. The K m and V max values of purified Car19 were 0.061 mg mL −1 and 115.13 U mg −1 , respectively, with κ‐carrageenan as substrate. Thin‐layer chromatography and electrospray ionization mass‐spectrometry analysis of hydrolysates indicated that the enzyme exolytically depolymerized κ‐carrageenan to neo‐carrabiose. The hydrolysate enhanced the resistance of cucumber to cucumber mosaic virus and increased the activity of antioxidant enzymes in infected plants. Conclusion To our knowledge, Car19 is the most thermostable κ‐carrageenase reported so far. Its high optimal reaction temperature and thermostability, and unitary hydrolysate constituent, makes Car19 a promising candidate for the preparation of carrageenan oligosaccharides with plant protection activity. © 2018 Society of Chemical Industry
Quantitative proteome analysis of bovine mammary gland reveals protein dynamic changes involved in peak and late lactation stages
Highlights: • Revealed dynamic protein changes between two lactation stages in bovine mammary by TMT-based proteomics (first time). • Longitudinal design avoided the influence of different genetic backgrounds on the DEP detection. • 179 differentially expressed proteins (DEPs) identified. • Identified novel DEPs: AACS, DHCR7, GSTM3, SFRP1 and SFRP4. • Major pathways: PI3K-Akt, localization, lipid metabolic, amino acid transport immune system and apoptotic signaling. Mammary gland is an important organ for milk synthesis and secretion. It undergoes dramatic physiological changes to adapt the shift from peak to late lactation stage. Protein plays a final very vital role in many life functions, and the protein changes during different lactation stages potentially reflect the biology of lactation and the functions of mammary gland in cows. In current study, we adopted tandem mass tags label-based quantitative analysis technique and to investigate proteome changes occurring in bovine mammary gland from peak to late lactation stages. A total of 3753 proteins from mammary tissues taken at two lactation points from four individual cows by biopsy were quantified, out of which 179 proteins were expressed differentially between two stages. We observed five new DEPs (AACS, DHCR7, GSTM3, SFRP1 and SFRP4) and nine functional well-studies known proteins (PLIN2, LPIN1, PLIN3, GSN, CD74, MMP2, SOD1, SOD3 and GPX3) related to milk performance and mammary morphology. Bioinformatics analyses of the DEPs showed a majority of the up-regulated proteins during late lactation stage were related to apoptosis and immune process, while the downregulated proteins were mainly involved in localization, lipid metabolic and transport process. This suggests that the mammary gland can adapt to different molecular functions according to the biological need of the animal. From the integrated analysis of the differentially expressed proteins with known quantitative trait loci and genome-wide association study data, we identified 95 proteins may potentially affect milking performance. We expect findings in this study could be a valuable resource for future studies investigating the bovine proteome and functional studies.
CD147-induced cell proliferation is associated with Smad4 signal inhibition
CD147 is a multifunctional trans-membrane glycoprotein, which is highly expressed in many cancers. However, the mechanism by which CD147 modulates cell proliferation is not fully understood. The aim of this study is to investigate the role of CD147 in cell proliferation associated with the TGF-β/Smad4 signaling pathway. Here, we used cell viability and clone formation assays in LNCaP prostate cancer cells to demonstrate that CD147 promotes cell proliferation. The luciferase assay and western blotting show that silencing CD147 using shRNA enhances transcription and expression of p21{sup WAF1}. Using immunofluorescence and nuclear-cytoplasmic separation, we show that this is primarily attributed to transport of Smad4 from the cytoplasm to nucleus. Other assays (GST pull-down, co-immunoprecipitation and immunofluorescence) demonstrate that Smad4 is a new interaction partner of CD147, with the Smad4 MH2 domain and CD147 intracellular domain (CD147-ICD) being involved in the interaction. Furthermore, we report that a phosphoserine (pSer) in CD147 (pSer252) is responsible for this interaction and inhibition of the Smad4/p21{sup WAF1} signal that promotes cell proliferation. Our results provide a novel molecular mechanism for CD147-induced cell proliferation associated with Smad4 signal inhibition. - Highlights: • Smad4 interacts with CD147 via the MH2 domain. • CD147 prevents Smad4 translocation into the nuclear to regulate p21 transcription. • CD147 inhibits p21 transcription and expression independent on p53. • pCD147-S252 is responsible for interaction with Smad4 and p21 down-regulation.
Free-Standing Self-Assemblies of Gallium Nitride Nanoparticles: A Review
Gallium nitride (GaN) is an III-V semiconductor with a direct band-gap of 3 . 4 e V . GaN has important potentials in white light-emitting diodes, blue lasers, and field effect transistors because of its super thermal stability and excellent optical properties, playing main roles in future lighting to reduce energy cost and sensors to resist radiations. GaN nanomaterials inherit bulk properties of the compound while possess novel photoelectric properties of nanomaterials. The review focuses on self-assemblies of GaN nanoparticles without templates, growth mechanisms of self-assemblies, and potential applications of the assembled nanostructures on renewable energy.
A high-performance broadband terahertz absorber based on sawtooth-shape doped-silicon
Perfect absorbers with broadband absorption of terahertz (THz) radiation are promising for applications in imaging and detection to enhance the contrast and sensitivity, as well as to provide concealment. Different from previous two-dimensional structures, here we put forward a new type of THz absorber based on sawtooth-shape doped-silicon with near-unit absorption across a broad spectral range. Absorbance over 99% is observed numerically from 1.2 to 3 THz by optimizing the geometric parameters of the sawtooth structure. Our absorbers can operate over a wide range of incident angle and are polarization insensitive. The underlying mechanisms due to the combination of an air-cavity mode and mode-matching resonance on the air-sawtooth interface are analyzed in terms of the field patterns and electromagnetic power loss features.
Effect of microstructural features on the laser efficiency of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics
The optical properties and microstructure of transparent Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics synthesised by different reactive sintering routes are studied. It is found that the residual porosity of optical ceramics is directly related to the homogeneity of the microstructure of initial compacts, which can be estimated by the existence of particle agglomerates larger than 1 mm in initial nanopowders. A qualitative correlation is established between the residual porosity, the optical losses and the lasing slope efficiency of Nd{sup 3+}:Y{sub 3}Al{sub 5}O{sub 12} ceramics. The maximum laser efficiency (η = 49%) was observed in the samples with the lowest porosity (2.3 × 10{sup -3} vol %). (lasers)
Effects of layer-multiplying and interface on the content of β-transcrystallization in PP
The alternating multilayered polypropylene (PP layer)/β-nucleating agent filled-polypropylene (β-PP layer) were prepared through layer-multiplying extrusion combined with an assembly of layer-multiplying elements (LM Es). The content of β-crystal was firstly evaluated by differential scanning calorimetry (DSC), which indicated that the relative amount of the β-crystal increased from 38.67% to 81.22% with the increase of layer numbers from 2-layer to 128-layer. It was well consistent with the results of X-ray diffraction (XRD). The morphology observation of β-crystal by polarizing microscope (POM) revealed that the closely packed nuclei in the interface could induce numerous β-transcrystallization in pure PP layer due to the confinement effect. The non-isothermal crystallization kinetic analysis via Mozhishen’s methods manifested that the crystallization rate was greatly enhanced by the augment of the layered interface.
MiR-29b inhibits collagen maturation in hepatic stellate cells through down-regulating the expression of HSP47 and lysyl oxidase
Highlights: • Enhanced HSP47 and LOX expression is associated with decreased miR-29b level in liver fibrosis. • miR-29b down-regulates HSP47 and LOX expression. • The suppression of HSP47 and LOX by miR-29b is mediated by putative sites at their 3′-UTRs. • miR-29b inhibits extracellular LOX activity and collagen maturation. - Abstract: Altered expression of miR-29b is implicated in the pathogenesis and progression of liver fibrosis. We and others previously demonstrated that miR-29b down-regulates the expression of several extracellular-matrix (ECM) genes including Col 1A1, Col 3A1 and Elastin via directly targeting their 3′-UTRs. However, whether or not miR-29b plays a role in the post-translational regulation of ECM biosynthesis has not been reported. Heat shock protein 47 (HSP47) and lysyl oxidase (LOX) are known to be essential for ECM maturation. In this study we have demonstrated that expression of HSP47 and LOX was significantly up-regulated in culture-activated primary rat hepatic stellate cells (HSCs), TGF-β stimulated LX-2 cells and liver tissue of CCl{sub 4}-treated mice, which was accompanied by a decrease of miR-29b level. In addition, over-expression of miR-29b in LX-2 cells resulted in significant inhibition on HSP47 and LOX expression. Mechanistically, miR-29b inhibited the expression of a reporter gene that contains the respective full-length 3′-UTR from HSP47 and LOX gene, and this inhibitory effect was abolished by the deletion of a putative miR-29b targeting sequence from the 3′-UTRs. Transfection of LX-2 cells with miR-29b led to abnormal collagen structure as shown by electron-microscopy, presumably through down-regulation of the expression of molecules involved in ECM maturation including HSP47 and LOX. These results demonstrated that miR-29b is involved in regulating the post-translational processing of ECM and fibril formation.
Efficient terahertz wave generation from GaP crystals pumped by chirp-controlled pulses from femtosecond photonic crystal fiber amplifier
A chirp-tunable femtosecond 10 W, 42 MHz photonic-crystal-fiber oscillator-amplifier system that is capable of delivering sub-60 fs light pulses at 1040 nm is used to demonstrate high-efficiency terahertz radiation generation via optical rectification in GaP crystals only a few millimeters in length. The optimization of the chirp of the fiber-laser pulses is shown to radically enhance the terahertz output, indicating one possible way to more efficiently use these extended nonlinear crystals in compact fiber-pumped terahertz radiation sources.
A Systematic Approach for Real-Time Operator Functional State Assessment
A task overload condition often leads to high stress for an operator, causing performance degradation and possibly disastrous consequences. Just as dangerous, with automated flight systems, an operator may experience a task underload condition (during the en-route flight phase, for example), becoming easily bored and finding it difficult to maintain sustained attention. When an unexpected event occurs, either internal or external to the automated system, the disengaged operator may neglect, misunderstand, or respond slowly/inappropriately to the situation. In this paper, we discuss an approach for Operator Functional State (OFS) monitoring in a typical aviation environment. A systematic ground truth finding procedure has been designed based on subjective evaluations, performance measures, and strong physiological indicators. The derived OFS ground truth is continuous in time compared to a very sparse estimation of OFS based on an expert review or subjective evaluations. It can capture the variations of OFS during a mission to better guide through the training process of the OFS assessment model. Furthermore, an OFS assessment model framework based on advanced machine learning techniques was designed and the systematic approach was then verified and validated with experimental data collected in a high fidelity Boeing 737 simulator. Preliminary results show highly accurate engagement/disengagement detection making it suitable for real-time applications to assess pilot engagement.