Yeast perilipin Pet10p/Pln1p interacts with Erg6p in ergosterol metabolism.

Lipid droplets (LD) are highly dynamic organelles specialized for the regulation of energy storage and cellular homeostasis. LD consist of a neutral lipid core surrounded by a phospholipid monolayer membrane with embedded proteins, most of which are involved in lipid homeostasis. In this study, we focused on one of the major LD proteins, sterol C24-methyltransferase, encoded by ERG6. We found that the absence of Erg6p resulted in an increased accumulation of yeast perilipin Pet10p in LD, while the disruption of PET10 was accompanied by Erg6p LD over-accumulation. An observed reciprocal enrichment of Erg6p and Pet10p in pet10Δ and erg6Δ mutants in LD, respectively, was related to specific functional changes in the LD and was not due to regulation on the expression level. The involvement of Pet10p in neutral lipid homeostasis was observed in experiments that focused on the dynamics of neutral lipid mobilization as time-dependent changes in the triacylglycerols (TAG) and steryl esters (SE) content. We found that the kinetics of SE hydrolysis was reduced in erg6Δ cells and the mobilization of SE was completely lost in mutants that lacked both Erg6p and Pet10p. In addition, we observed that decreased levels of SE in erg6Δpet10Δ was linked to an overexpression of steryl ester hydrolase Yeh1p. Lipid analysis of erg6Δpet10Δ showed that PET10 deletion altered the composition of ergosterol intermediates which had accumulated in erg6Δ. In conclusion, yeast perilipin Pet10p functionally interacts with Erg6p during the metabolism of ergosterol.

Syncytin-mediated open-ended membrane tubular connections facilitate the intercellular transfer of cargos including Cas9 protein.

Much attention has been focused on the possibility that cytoplasmic proteins and RNA may be conveyed between cells in extracellular vesicles (EVs) and tunneling nanotube (TNT) structures. Here, we set up two quantitative delivery reporters to study cargo transfer between cells. We found that EVs are internalized by reporter cells but do not efficiently deliver functional Cas9 protein to the nucleus. In contrast, donor and acceptor cells co-cultured to permit cell contact resulted in a highly effective transfer. Among our tested donor and acceptor cell pairs, HEK293T and MDA-MB-231 recorded optimal intercellular transfer. Depolymerization of F-actin greatly decreased Cas9 transfer, whereas inhibitors of endocytosis or knockdown of genes implicated in this process had little effect on transfer. Imaging results suggest that intercellular transfer of cargos occurred through open-ended membrane tubular connections. In contrast, cultures consisting only of HEK293T cells form close-ended tubular connections ineffective in cargo transfer. Depletion of human endogenous fusogens, syncytins, especially syncytin-2 in MDA-MB-231 cells, significantly reduced Cas9 transfer. Full-length mouse syncytin, but not truncated mutants, rescued the effect of depletion of human syncytins on Cas9 transfer. Mouse syncytin overexpression in HEK293T cells partially facilitated Cas9 transfer among HEK293T cells. These findings suggest that syncytin may serve as the fusogen responsible for the formation of an open-ended connection between cells.

Communication between cells is an important process for survival, especially in multicellular organisms. Cells typically exchange information by releasing small molecules in to their surrounding environment which neighboring cells then receive and respond to. However, there is growing evidence to suggest that cells also pass signals to each other via fatty bubbles called exosomes and tubes connecting their membranes. Various reports have suggested that these mechanisms can transport larger proteins and nucleic acids which carry the information cells need to make proteins. However, how cells are able to combine their membranes to allow these types of transfer is unclear. To investigate, Zhang and Schekman studied how human cancer cells and embryonic cells grown in a laboratory pass molecules between each other. This included a string of nucleic acids known as RNA and a protein called Cas9 which can edit the genome of cells to activate an enzyme that has bioluminescence activity. By measuring the level of luminescence, Zhang and Schekman were able to sensitively detect the transfer of Cas9 and RNA to neighboring cells. The experiments showed that exosomes were not efficient at transporting proteins or RNA. However, cells in near or direct contact transferred both molecules effectively using tube connections, with some cell types being more adept at this mechanism than others. Zhang and Schekman found that the formation of these tubular channels required a protein called syncytin which helps membranes fuse together mainly in the early stages of embryo development. These findings open a new avenue of investigation on how cells send signals to one another. It is also possible that the protein syncytin has a role in cancer progression, as tumors rely on cell communication to maintain their growth and organize the cells surrounding them. However, further work is needed to investigate this possibility.

Brownian Motion Simulation for Estimating Chloride Diffusivity of Cement Paste.

Chloride ion diffusion properties are important factors that affect the durability of cementitious materials. Researchers have conducted much exploration in this field, both experimentally and theoretically. Numerical simulation techniques have been greatly improved as theoretical methods and testing techniques have been updated. Researchers have modeled cement particles mostly as circular shapes, simulated the diffusion of chloride ions, and derived chloride ion diffusion coefficients in two-dimensional models. In this paper, a three-dimensional random walk method based on Brownian motion is employed to evaluate the chloride ion diffusivity of cement paste with the use of numerical simulation techniques. Unlike previous simplified two-dimensional or three-dimensional models with restricted walks, this is a true three-dimensional simulation technique that can visually represent the cement hydration process and the diffusion behavior of chloride ions in cement paste. During the simulation, the cement particles were reduced to spheres, which were randomly distributed in a simulation cell with periodic boundary conditions. Brownian particles were then dropped into the cell and permanently captured if their initial position in the gel fell. Otherwise, a sphere tangential to the nearest cement particle was constructed, with the initial position as the center. Then, the Brownian particles randomly jumped to the surface of this sphere. The process was repeated to derive the average arrival time. In addition, the diffusion coefficient of chloride ions was deduced. The effectiveness of the method was also tentatively confirmed by the experimental data.

Predicting Elastic Constants of Refractory Complex Concentrated Alloys Using Machine Learning Approach.

Refractory complex concentrated alloys (RCCAs) have drawn increasing attention recently owing to their balanced mechanical properties, including excellent creep resistance, ductility, and oxidation resistance. The mechanical and thermal properties of RCCAs are directly linked with the elastic constants. However, it is time consuming and expensive to obtain the elastic constants of RCCAs with conventional trial-and-error experiments. The elastic constants of RCCAs are predicted using a combination of density functional theory simulation data and machine learning (ML) algorithms in this study. The elastic constants of several RCCAs are predicted using the random forest regressor, gradient boosting regressor (GBR), and XGBoost regression models. Based on performance metrics R-squared, mean average error and root mean square error, the GBR model was found to be most promising in predicting the elastic constant of RCCAs among the three ML models. Additionally, GBR model accuracy was verified using the other four RHEAs dataset which was never seen by the GBR model, and reasonable agreements between ML prediction and available results were found. The present findings show that the GBR model can be used to predict the elastic constant of new RHEAs more accurately without performing any expensive computational and experimental work.

Electrochemical Energy Storage Properties of High-Porosity Foamed Cement.

Foamed porous cement materials were fabricated with H2O2 as foaming agent. The effect of H2O2 dosage on the multifunctional performance is analyzed. The result shows that the obtained specimen with 0.6% H2O2 of the ordinary Portland cement mass (PC0.6) has appropriate porosity, leading to outstanding multifunctional property. The ionic conductivity is 29.07 mS cm-1 and the compressive strength is 19.6 MPa. Furthermore, the electrochemical energy storage performance is studied in novel ways. The PC0.6 also shows the highest areal capacitance of 178.28 mF cm-2 and remarkable cycle stability with 90.67% of initial capacitance after 2000 cycles at a current density of 0.1 mA cm-2. The superior electrochemical energy storage property may be attributed to the high porosity of foamed cement, which enlarges the contact area with the electrode and provides a rich ion transport channel. This report on cement-matrix materials is of great significance for large scale civil engineering application.

A Three-Dimensional Random Walk Algorithm for Estimating the Chloride Diffusivity of Concrete.

The chloride diffusivity of concrete is an important parameter for assessing the long-term durability of coastal concrete structures. The purpose of this paper is to present a three-dimensional random walk algorithm (RWA) for estimating the chloride diffusivity of concrete. By analyzing the size distribution of aggregates, the equivalent interfacial transition zone (ITZ) thickness is derived in an analytical manner. Each aggregate is combined with the surrounding ITZ to construct an equivalent aggregate model (EAM) and the chloride diffusivity is formulated. It is found that the equivalent ITZ thickness decreases with the increase of practical ITZ thickness and aggregate volume fraction. The aggregate gradation influences the equivalent ITZ thickness to a certain extent. The relative chloride diffusivity of the equivalent aggregate is almost directly and inversely proportional to the equivalent ITZ thickness and the aggregate radius, respectively. The numerical results show that, when the EAM is adopted, the computational time is greatly reduced. With the EAM, concrete can be modeled as a two-phase material and the chloride diffusivity is estimated by applying the RWA. It is shown that, with the increase of mean square displacement and number of Brownian particles, the average chloride diffusivity of concrete approaches a stable value. Finally, through comparison with experimental data, the validation of the RWA is preliminarily verified.

Carbide Formation in Refractory Mo15Nb20Re15Ta30W20 Alloy under a Combined High-Pressure and High-Temperature Condition.

In this work, the formation of carbide with the concertation of carbon at 0.1 at.% in refractory high-entropy alloy (RHEA) Mo15Nb20Re15Ta30W20 was studied under both ambient and high-pressure high-temperature conditions. The x-ray diffraction of dilute carbon (C)-doped RHEA under ambient pressure showed that the phases and lattice constant of RHEA were not influenced by the addition of 0.1 at.% C. In contrast, C-doped RHEA showed unexpected phase formation and transformation under combined high-pressure and high-temperature conditions by resistively employing the heated diamond anvil cell (DAC) technique. The new FCC_L12 phase appeared at 6 GPa and 809 °C and preserved the ambient temperature and pressure. High-pressure and high-temperature promoted the formation of carbides Ta3C and Nb3C, which are stable and may further improve the mechanical performance of the dilute C-doped alloy Mo15Nb20Re15Ta30W20.

Insight the process of hydrazine gas adsorption on layered WS2: a first principle study.

The process of hydrazine gas adsorption on layered WS2 has been systematically studied from first principle calculations. Our results demonstrate that this adsorption process is exothermic, and hydrazine molecules are physically adsorbed. The layer-dependent adsorption energy and interlayer separation induced by van der Waals interaction exerted by hydrazine molecules lead to the difficulty in desorbing hydrazine molecules from layered WS2 as the number of layers increases. The most interesting finding is the emergence of localized impurity states below the Fermi level upon the hydrazine adsorption, irrespective of the number of WS2 layers, resulting in a significant effect on the band structures and subsequently changing its electrical conductivity. Furthermore, a layer-dependent small charge transfer occurs between hydrazine and layered WS2, leading to a charge redistribution and considerable polarization in the adsorbed systems. The existence of defects and the humidity, on the other hand, influences the sensitivity of layered WS2 to the hydrazine adsorption. Obtained results show that a perfectly layered WS2 might be a promising candidate as an efficient nanosensor to detect such toxic gas in dry environment.

Gas adsorption and light interaction mechanism in phosphorene-based field-effect transistors.

Phosphorene-based field effect transistor (FET) structures were fabricated to study the gas- and photo-detection properties of phosphorene. The interplay between device performance and environmental conditions was probed and analyzed using in situ transport measurements. The device structures were exposed to different chemical and light environments to understand how they perform under different external stimuli. For the gas/molecule detection studies, inert (Ar), as well as, oxidizing (N2O), and reducing (H2 and also N2H4) agents were selected. The FET structure was exposed to these different gases, and the effect of each gas on the device resistance was measured. The study showed varying response towards different molecules. Specifically, no significant resistance change was observed upon exposure to Ar, while H2 and N2H4 were found to decrease the resistance and N2O had the opposite effect resulting in an increase in resistance. This work is the first demonstration for the detection of N2H2 and N2O using a phosphorene-based system. These phosphorene-based FET structures were also found to be sensitive to light exposure. When such structure was irradiated with light, the current modulation was lost. The observed resistance changes can be explained as a result of the modulation of the Schottky barrier at the phosphorene-electrical contact interface due to the adsorbed molecules and charge transfer, and/or photo-induced carrier generation. The results were consistent with the transfer characteristics of Vdsvs. Vg.

Metallic nanoparticles induced antibiotic resistance genes attenuation of leachate culturable microbiota: The combined roles of growth inhibition, ion dissolution and oxidative stress.

The dissemination and propagation of antibiotic resistance genes (ARGs) is an emerging global health concern, and the potential effects of nanomaterials on ARGs fates have drawn much attention recently. In the current study, the effects of metallic nanoparticles on ARGs occurrence of leachate culturable microbiota were investigated by four typical metal and metal oxide nanoparticles (Cu, Zn, CuO, and ZnO). The ARGs diversity was remarkably decreased during the cultivation and enrichment of leachate microbiota, and their abundances decreased for 1.4-3.2 orders of magnitude. The presence of nanoparticles facilitated the ARGs attenuation, and the magnitude of effects depended on types of nanoparticles and ARGs. Metal oxide nanoparticles caused more remarkable effects than metal nanoparticles. Mechanism analysis indicated that bacterial growth was inhibited, and the dissolved metal ions from nanoparticles partially contributed to nanoparticles decreasing ARGs. Flow cytometry experiments further confirmed that nanoparticles could enter bacterial cells, and then induce excessive reactive oxygen species (ROS) generation and increase membrane permeability. Finally, the possible mechanisms were put forward, and the structural equation models (SEM) differentiated the contribution of different factors shaping ARGs. The dissolved metal ions and growth inhibition caused by nanoparticles decreased ARGs transfer frequencies via exerting excessive metal stress and lowering population density. On the other hand, nanoparticles were incorporated into the cells, and then induced the generation of ROS, which might facilitate ARGs horizontal transfer via increasing membrane permeability, or decrease ARGs via the damage of genomic and plasmid DNA. Therefore, nanoparticles could affect ARGs fates via several ways, and combined effects finally determined the ARGs variations.

Bilayer phosphorene under high pressure: in situ Raman spectroscopy.

In this study, bilayer phosphorene samples were subjected to high pressure using a Diamond Anvil Cell (DAC) and their vibrational properties were studied via in situ Raman spectroscopy. Systematic shifting in the Raman frequency of A1g, B2g, and A2g modes was observed and theoretical calculations were performed to understand the relationship between the strain and the vibrational properties. The changes in the vibration modes under high pressure are found to reflect the deformation in the structure and its stiffness. Firstly, the study shows a substantial pressure-induced enhancement of the interactions between atoms for the out-plane mode A1g, mainly due to the directional nature of the lone pair of electrons and charge transfer. However, these interactions and the observed blue shift of the A1g Raman peak are much weaker than those in bulk black phosphorous. Secondly, while a significant enhancement of the atomic interactions due to bond length change is also observed for the in-plane mode B2g along the zigzag direction, there is almost negligible effect on the in-plane mode A2g along the armchair direction. The results add to the knowledge on mechanical properties and strain engineering in phosphorene towards novel functionalities and applications of this intriguing two-dimensional (2D) material.

The New Face of the Lipid Droplet: Lipid Droplet Proteins.

The lipid droplet (LD) is an organelle with vital functions found in nearly all organisms. LD proteomic research has provided fundamentally important insights into this organelle's functions. The review provides a summary of LD proteomic studies conducted across diverse organisms and cell and tissue types. The accumulated proteomic data are reviewed for evidence of a protein targeting mechanism for the organelle. The hypotheses for several specific localization mechanisms based on what is known about targeting mechanisms for other organelles and vesicles are provided. Although the nature of the mechanism is not known, the functional data demonstrate that the targeting mechanism and, indeed, the organelle itself, is conserved from prokaryotes to eukaryotes. It is hoped that the review will help inspire further research leading to novel discoveries in the field.

Hydroxysteroid dehydrogenase family proteins on lipid droplets through bacteria, C. elegans, and mammals.

Lipid droplets (LDs) are the main fat storing sites in almost all species from bacteria to humans. The perilipin family has been found as LD proteins in mammals, Drosophila, and a couple of slime molds, but no bacterial LD proteins containing sequence conservation were identified. In this study, we reported that the hydroxysteroid dehydrogenase (HSD) family was found on LDs across all organisms by LD proteomic analysis. Imaging experiments confirmed LD targeting of three representative HSD proteins including ro01416 in RHA1, DHS-3 in C. elegans, and 17ß-HSD11 in human cells. In C. elegans, 17ß-HSD11 family proteins (DHS-3, DHS-4 and DHS-19) were localized on LDs in distinct tissues. In intestinal cells of C. elegans, DHS-3 targeted to cytoplasmic LDs, while DHS-9 labeled nuclear LDs. Furthermore, the N-terminal hydrophobic domains of 17ß-HSD11 family were necessary for their targeting to LDs. Last, 17ß-HSD11 family proteins induced LD aggregation, and deletion of DHS-3 in C. elegans caused lipid decrease. Independent of their presumptive catalytic sites, 17ß-HSD11 family proteins regulated LD dynamics and lipid metabolism through affecting the LD-associated ATGL, which was conserved between C. elegans and humans. Together, these findings for HSDs provide a new insight not only into the mechanistic studies of the dynamics and functions of LDs in multiple organisms, but also into understanding the evolutionary history of the organelle.

The lipid droplet: A conserved cellular organelle.

The lipid droplet (LD) is a unique multi-functional organelle that contains a neutral lipid core covered with a phospholipid monolayer membrane. The LDs have been found in almost all organisms from bacteria to humans with similar shape. Several conserved functions of LDs have been revealed by recent studies, including lipid metabolism and trafficking, as well as nucleic acid binding and protection. We summarized these findings and proposed a hypothesis that the LD is a conserved organelle.

Bacterial lipid droplets bind to DNA via an intermediary protein that enhances survival under stress.

Lipid droplets (LDs) are multi-functional organelles consisting of a neutral lipid core surrounded by a phospholipid monolayer, and exist in organisms ranging from bacteria to humans. Here we study the functions of LDs in the oleaginous bacterium Rhodococcus jostii. We show that these LDs bind to genomic DNA through the major LD protein, MLDS, which increases survival rate of the bacterial cells under nutritional and genotoxic stress. MLDS expression is regulated by a transcriptional regulator, MLDSR, that binds to the operator and promoter of the operon encoding both proteins. LDs sequester MLDSR, controlling its availability for transcriptional regulation. Our findings support the idea that bacterial LDs can regulate nucleic acid function and facilitate bacterial survival under stress.

The prospects of phosphorene as an anode material for high-performance lithium-ion batteries: a fundamental study.

To completely understand lithium adsorption, diffusion, and capacity on the surface of phosphorene and, therefore, the prospects of phosphorene as an anode material for high-performance lithium-ion batteries (LIBs), we carried out density-functional-theory calculations and studied the lithium adsorption energy landscape, the lithium diffusion mobility, the lithium intercalation, and the lithium capacity of phosphorene. We also carried out, for the very first time, experimental measurement of the lithium capacity of phosphorene. Our calculations show that the lithium diffusion mobility along the zigzag direction in the valley of phosphorene was about 7 to 11 orders of magnitude faster than that along the other directions, indicating its ultrafast and anisotropic diffusivity. The lithium intercalation in phosphorene was studied by considering various Li n P16 configurations (n = 1-16) including single-side and double-side adsorptions. We found that phosphorene could accommodate up to a ratio of one Li per P atom (i.e. Li16P16). In particular, we found that, even at a high Li concentration (e.g. x = 1 in Li x P), there was no lithium clustering, and the structure of phosphorene (when fractured) is reversible during lithium intercalation. The theoretical value of the lithium capacity for a monolayer phosphorene is predicted to be above 433 mAh g-1, depending on whether Li atoms are adsorbed on the single side or the double side of phosphorene. Our experimental measurement of the lithium capacity for few-layer phosphorene networks shows a reversible stable value of ∼453 mAh g-1 even after 50 cycles. Our results clearly show that phosphorene, compared to graphene and other two-dimensional materials, has great promise as a novel anode material for high-performance LIBs.

Dynamics of the lipid droplet proteome of the Oleaginous yeast rhodosporidium toruloides.

Lipid droplets (LDs) are ubiquitous organelles that serve as a neutral lipid reservoir and a hub for lipid metabolism. Manipulating LD formation, evolution, and mobilization in oleaginous species may lead to the production of fatty acid-derived biofuels and chemicals. However, key factors regulating LD dynamics remain poorly characterized. Here we purified the LDs and identified LD-associated proteins from cells of the lipid-producing yeast Rhodosporidium toruloides cultured under nutrient-rich, nitrogen-limited, and phosphorus-limited conditions. The LD proteome consisted of 226 proteins, many of which are involved in lipid metabolism and LD formation and evolution. Further analysis of our previous comparative transcriptome and proteome data sets indicated that the transcription level of 85 genes and protein abundance of 77 proteins changed under nutrient-limited conditions. Such changes were highly relevant to lipid accumulation and partially confirmed by reverse transcription-quantitative PCR. We demonstrated that the major LD structure protein Ldp1 is an LD marker protein being upregulated in lipid-rich cells. When overexpressed in Saccharomyces cerevisiae, Ldp1 localized on the LD surface and facilitated giant LD formation, suggesting that Ldp1 plays an important role in controlling LD dynamics. Our results significantly advance the understanding of the molecular basis of lipid overproduction and storage in oleaginous yeasts and will be valuable for the development of superior lipid producers.

Integrated omics study delineates the dynamics of lipid droplets in Rhodococcus opacus PD630.

Rhodococcus opacus strain PD630 (R. opacus PD630), is an oleaginous bacterium, and also is one of few prokaryotic organisms that contain lipid droplets (LDs). LD is an important organelle for lipid storage but also intercellular communication regarding energy metabolism, and yet is a poorly understood cellular organelle. To understand the dynamics of LD using a simple model organism, we conducted a series of comprehensive omics studies of R. opacus PD630 including complete genome, transcriptome and proteome analysis. The genome of R. opacus PD630 encodes 8947 genes that are significantly enriched in the lipid transport, synthesis and metabolic, indicating a super ability of carbon source biosynthesis and catabolism. The comparative transcriptome analysis from three culture conditions revealed the landscape of gene-altered expressions responsible for lipid accumulation. The LD proteomes further identified the proteins that mediate lipid synthesis, storage and other biological functions. Integrating these three omics uncovered 177 proteins that may be involved in lipid metabolism and LD dynamics. A LD structure-like protein LPD06283 was further verified to affect the LD morphology. Our omics studies provide not only a first integrated omics study of prokaryotic LD organelle, but also a systematic platform for facilitating further prokaryotic LD research and biofuel development.

Microorganism lipid droplets and biofuel development.

Lipid droplet (LD) is a cellular organelle that stores neutral lipids as a source of energy and carbon. However, recent research has emerged that the organelle is involved in lipid synthesis, transportation, and metabolism, as well as mediating cellular protein storage and degradation. With the exception of multi-cellular organisms, some unicellular microorganisms have been observed to contain LDs. The organelle has been isolated and characterized from numerous organisms. Triacylglycerol (TAG) accumulation in LDs can be in excess of 50% of the dry weight in some microorganisms, and a maximum of 87% in some instances. These microorganisms include eukaryotes such as yeast and green algae as well as prokaryotes such as bacteria. Some organisms obtain carbon from CO2 via photosynthesis, while the majority utilizes carbon from various types of biomass. Therefore, high TAG content generated by utilizing waste or cheap biomass, coupled with an efficient conversion rate, present these organisms as bio-tech 'factories' to produce biodiesel. This review summarizes LD research in these organisms and provides useful information for further LD biological research and microorganism biodiesel development.