Chemical functionalization of low-dimensional materials such as nanotubes, nanowires and graphene leads to profound changes in their properties and is essential for solubilizing them in common ...solvents. Covalent attachment of functional groups is generally achieved at defect sites, which facilitate electron transfer. Here, we describe a simple and general method for covalent functionalization of two-dimensional transition metal dichalcogenide nanosheets (MoS₂, WS₂ and MoSe₂), which does not rely on defect engineering. The functionalization reaction is instead facilitated by electron transfer between the electron-rich metallic 1T phase and an organohalide reactant, resulting in functional groups that are covalently attached to the chalcogen atoms of the transition metal dichalcogenide. The attachment of functional groups leads to dramatic changes in the optoelectronic properties of the material. For example, we show that it renders the metallic 1T phase semiconducting, and gives it strong and tunable photoluminescence and gate modulation in field-effect transistors.
The excellent catalytic activity of metallic MoS2 edges for the hydrogen evolution reaction (HER) has led to substantial efforts towards increasing the edge concentration. The 2H basal plane is less ...active for the HER because it is less conducting and therefore possesses less efficient charge transfer kinetics. Here we show that the activity of the 2H basal planes of monolayer MoS2 nanosheets can be made comparable to state-of-the-art catalytic properties of metallic edges and the 1T phase by improving the electrical coupling between the substrate and the catalyst so that electron injection from the electrode and transport to the catalyst active site is facilitated. Phase-engineered low-resistance contacts on monolayer 2H-phase MoS2 basal plane lead to higher efficiency of charge injection in the nanosheets so that its intrinsic activity towards the HER can be measured. We demonstrate that onset potentials and Tafel slopes of ∼-0.1 V and ∼50 mV per decade can be achieved from 2H-phase catalysts where only the basal plane is exposed. We show that efficient charge injection and the presence of naturally occurring sulfur vacancies are responsible for the observed increase in catalytic activity of the 2H basal plane. Our results provide new insights into the role of contact resistance and charge transport on the performance of two-dimensional MoS2 nanosheet catalysts for the HER.
The spread of non-native species has been a subject of increasing concern since the 1980s when human-mediated transportation, mainly related to ships' ballast water, was recognized as a major vector ...for species transportation and spread, although records of non-native species go back as far as 16th Century. Ever increasing world trade and the resulting rise in shipping have highlighted the issue, demanding a response from the international community to the threat of non-native marine species. In the present study, we searched for available literature and databases on shipping and invasive species in the North-eastern (NE) and South-western (SW) Atlantic Ocean and assess the risk represented by the shipping trade between these two regions. There are reports of 44 species associated with high impacts for the NE Atlantic and 15 for the SW Atlantic, although this may be an underestimate. Vectors most cited are ballast water and biofouling for both regions while aquaculture has also been a very significant pathway of introduction and spread of invasive species in the NE Atlantic. Although the two regions have significant shipping traffic, no exchange of invasive species could be directly associated to the shipping between the two regions. However, it seems prudent to bring the exchange of ballast water between the two regions under control as soon as possible.
•44 invasive species recorded for the NE Atlantic and 15 for the SW Atlantic.•Most cited vectors are ballast water and biofouling for both regions.•Aquaculture is a very significant pathway of invasive species in the NE Atlantic.•No exchange of species was directly associated with the shipping in the study area.
The presence of pesticides in fruits and vegetables has been a growing concern in Argentina. Only three of the major marketplaces there have the necessary infrastructure to determine pesticide ...residues in produce. The aim of this study was to investigate the presence of such residues in nationally produced fruits and vegetables for domestic consumption in order to evaluate the present state of the market. A total of 135 of the most widely consumed fruits and vegetables were analyzed for 35 pesticides. The analyses utilized a QuEChERS™ multiresidue-extraction kit along with tandem gas chromatography–mass spectrometry. The results were evaluated according to maximum residue limits (MRLs) for each commodity and pesticide according to national regulation. Pesticides were detected in 65% of the total samples, in 44% of the positive samples at or below the MRLs, and in 56% above the MRLs. Oranges had the highest pesticide concentration detected, but carrots had the highest frequency of noncompliance among the produce items sampled. Five pesticides were detected at frequencies above 10%, the highest being chlorpyrifos in 25.9% of the total samples. In other countries, the percentage of samples above the MLR is 4 times lower than our findings, and 7 times lower for exported products. An implementation of programs designed to facilitate awareness, capacitation, and monitoring is urgently recommended.
•Of 135 samples, 88 had at least one pesticide residue and 53 with two or more.•Of the positive samples, 39 were at or below and 49 above, the MRLs.•Chlorpyrifos was the most frequently found, but epoxiconazole was more often > MRL.•The produce-control system contains a significant degree of permeability.•The creation of programs to minimize exposure to pesticides via foodstuffs is urgent.
As biosensors and biomedical devices have become increasingly important to everyday diagnostics and monitoring, there are tremendous, and constant efforts towards developing and improving the ...reliability and versatility of such technology. As they offer high surface area-to-volume ratios and a diverse range of properties, from electronic to optical, two dimensional (2D) materials have proven to be very promising candidates for biological applications and technologies. Due to the dimensionality, 2D materials facilitate many interfacial phenomena that have shown to significantly improve the performance of biosensors, while recent advances in synthesis techniques and surface engineering methods also enable the realization of future biomedical devices. This short review aims to highlight the influence of 2D material surfaces and the properties that arise due to their 2D structure. Using recent (within the last few years) examples of biosensors and biomedical applications, we emphasize the important role of 2D materials in advancing developments and research for biosensing and healthcare.
This review highlights the importance of the dimensionality and surface interactions of 2D materials with examples of recent biosensing and biomedical applications.
The endoplasmic reticulum unfolded protein response (UPRER) is a cellular stress response that maintains homeostasis within the secretory pathway, regulates glucose and lipid metabolism, and ...influences longevity. To ask whether this role in lifespan determination depends upon metabolic intermediaries, we metabotyped C. elegans expressing the active form of the UPRER transcription factor XBP-1, XBP-1s, and found many metabolic changes. These included reduced levels of triglycerides and increased levels of oleic acid (OA), a monounsaturated fatty acid associated with lifespan extension in C. elegans. Here, we show that constitutive XBP-1s expression increases the activity of lysosomal lipases and upregulates transcription of the Δ9 desaturase FAT-6, which is required for the full lifespan extension induced by XBP-1s. Dietary OA supplementation increases the lifespan of wild-type, but not xbp-1s-expressing animals and enhances proteostasis. These results suggest that modulation of lipid metabolism by XBP-1s contributes to its downstream effects on protein homeostasis and longevity.
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•Xbp-1s expression decreases total fat but increases oleic acid (OA) levels•OA supplementation increases lifespan in wild-type, but not xbp-1-s-expressing, worms•Increased lysosomal lipase and Δ9 desaturase activity may underlie these changes•OA supplementation is sufficient to protect animals against proteotoxicity
Imanikia et al. find that expressing the transcription factor xbp-1s in C. elegans remodels lipid metabolism, decreasing triglyceride and increasing oleic acid (OA) levels. Increased OA levels may involve the activity of lysosomal lipases and a Δ9 desaturase, and are sufficient to increase lifespan and protect animals from proteotoxicity.
Shipping is recognised as an unintentional efficient pathway for spreading non-native species, harmful organisms and pathogens. In 2004, a unique IMO Convention was adopted to control and minimize ...this transfer in ship's ballast water. This Convention entered into force on 8th September 2017. However, unlikely the majority of IMO Conventions, the Ballast Water Management Convention requires ships to comply with biological standards (e.g. concentration of organisms per unit of volume in ballast water discharges). This study aimed to apply different techniques developed to measure concentrations of viable phytoplankton in natural and treated ballast water samples and compare them with the established flow cytometry method and vital staining microscopy. Samples were collected in the English Channel over one year and on-board during ballast water shipboard efficacy tests. Natural abundance of live phytoplankton varied from 23% to 89% of the total, while for cells larger than 10 μm (a size defined by the BWM Convention) the percentage varied from 3% to 60%. An overall good correlation was seen between the measurements taken with the two fluorometers and in comparison with the flow cytometry analysis, as found in previous studies. Analysis of treated ballast water samples showed a large variation in the number of viable cells, however indicating a low level of risk on all occasions for regulatory purposes. One of the key aspects to bear in mind when sampling and analysing for compliance is to be aware of the limitations of each technique.
•Different techniques have been proposed for measuring viable cells in ballast water.•Good correlation was seen between the measurements taken with the two fluorometers.•Treated ballast water analysis showed a large variation in the number of viable cells.•It is important to be aware of each technique's limitations for CME purposes.
Posttranscriptional modifications in transfer RNA (tRNA) are often critical for normal development because they adapt protein synthesis rates to a dynamically changing microenvironment. However, the ...precise cellular mechanisms linking the extrinsic stimulus to the intrinsic RNA modification pathways remain largely unclear. Here, we identified the cytosine-5 RNA methyltransferase NSUN2 as a sensor for external stress stimuli. Exposure to oxidative stress efficiently repressed NSUN2, causing a reduction of methylation at specific tRNA sites. Using metabolic profiling, we showed that loss of tRNA methylation captured cells in a distinct catabolic state. Mechanistically, loss of NSUN2 altered the biogenesis of tRNA-derived noncoding fragments (tRFs) in response to stress, leading to impaired regulation of protein synthesis. The intracellular accumulation of a specific subset of tRFs correlated with the dynamic repression of global protein synthesis. Finally, NSUN2-driven RNA methylation was functionally required to adapt cell cycle progression to the early stress response. In summary, we revealed that changes in tRNA methylation profiles were sufficient to specify cellular metabolic states and efficiently adapt protein synthesis rates to cell stress.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The aim of this work was to evaluate possible mechanisms involved in the protective effect of N-acetyl-L-cysteine (NAC) on hepatic endocrine-metabolic, oxidative stress, and inflammatory changes in ...prediabetic rats. For that, normal male Wistar rats (60 days old) were fed for 21 days with 10% sucrose in their drinking water and 5 days of NAC administration (50 mg/kg, i.p.) and thereafter, we determined: serum glucose, insulin, transaminases, uric acid, and triglyceride levels; hepatic fructokinase and glucokinase activities, glycogen content, lipogenic gene expression; enzymatic and non-enzymatic oxidative stress, insulin signaling pathway, and inflammatory markers. Results showed that alterations evinced in sucrose-fed rats (hypertriglyceridemia, hyperinsulinemia, and high liver fructokinase activity together with increased liver lipogenic gene expression and oxidative stress and inflammatory markers) were prevented by NAC administration. P-endothelial nitric oxide synthase (P-eNOS)/eNOS and pAKT/AKT ratios, decreased by sucrose ingestion, were restored after NAC treatment. In conclusion, the results suggest that NAC administration improves glucose homeostasis, oxidative stress, and inflammation in prediabetic rats probably mediated by modulation of the AKT/NOS pathway. Administration of NAC may be an effective complementary strategy to alleviate or prevent oxidative stress and inflammatory responses observed in type 2 diabetes at early stages of its development (prediabetes).
Objective:To determinate the recovery of total polyphenolic compounds content,in vitro antioxidant activity and HPLC/ESI/MS characterization of extract from Nephe-lium lappaceum L. (Mexican ...rambutan). Methods:The rambutan husk extract was obtained by aqueous extraction and a poly-phenolic fraction was recovered using Amberlite XAD-16. The total polyphenolic compounds content was determined by the Folin Ciocalteu and butanol-HCI methods. In vitro antioxidant activity was performed using ABTS and ferric reducing antioxidant power methods. Results:Mexican rambutan husk showed a total polyphenolic content of 582 mg/g and an evident antioxidant activity by ABTS and ferric reducing antioxidant power analysis. The HPLC/ESI/MS assay allowed the identification of 13 compounds,most of which belong to ellagitannins. Geraniin,corilagin and ellagic acid were present in the sample;the mineral composition was also evaluated. Conclusions:Rambutan husk cultivated in Mexico is a promising source for the re-covery of added value bioactive compounds with antioxidant activity,which have po-tential applications as bioactive antioxidant agents for the treatment of diseases.
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