A rapid and sensitive fluorescence sensing system for melamine based on charge transfer quenching of the fluorescence of graphene quantum dots (GQDs) in the presence of Hg2+ is proposed. The ...synthesized GQDs were strongly luminescent with predominantly aromatic sp2 domains. Melamine could coordinate with mercury through nitrogen atoms in both its amine and triazine groups and bring more Hg2+ to the surface of GQDs through π–π stacking, thus leading to quenching of the GQDs’ fluorescence. The quenching mechanism was investigated in detail and ascribed to charge transfer from the GQDs to Hg2+ with melamine acting as the linkage agent. The melamine demonstrated a linear range 0.15–20 μM and a detection limit of 0.12 μM, which was far below the regulatory level, suggesting the promising practical usage of this sensing system. This sensing system also possessed high selectivity for melamine in the presence of possible interferences. Finally, this novel sensor was successfully applied for melamine detection in raw milk and satisfactory recovery was achieved.
We describe a mammalian cell-based assay to identify coronavirus 3CL protease (3CLpro) inhibitors. This assay is based on rescuing protease-mediated cytotoxicity and does not require live virus. By ...enabling the facile testing of compounds across a range of 15 distantly related coronavirus 3CLpro enzymes, we identified compounds with broad 3CLpro-inhibitory activity. We also adapted the assay for use in compound screening and in doing so uncovered additional severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) 3CLpro inhibitors. We observed strong concordance between data emerging from this assay and those obtained from live-virus testing. The reported approach democratizes the testing of 3CLpro inhibitors by developing a simplified method for identifying coronavirus 3CLpro inhibitors that can be used by the majority of laboratories, rather than the few with extensive biosafety infrastructure. We identified two lead compounds, GC376 and compound 4, with broad activity against all 3CL proteases tested, including 3CLpro enzymes from understudied zoonotic coronaviruses.
Multiple coronavirus pandemics have occurred over the last 2 decades. This has highlighted a need to be proactive in the development of therapeutics that can be readily deployed in the case of future coronavirus pandemics. We developed and validated a simplified cell-based assay for the identification of chemical inhibitors of 3CL proteases encoded by a wide range of coronaviruses. This assay is reporter free, does not require specialized biocontainment, and is optimized for performance in high-throughput screening. By testing reported 3CL protease inhibitors against a large collection of 3CL proteases with variable sequence similarity, we identified compounds with broad activity against 3CL proteases and uncovered structural insights into features that contribute to their broad activity. Furthermore, we demonstrated that this assay is suitable for identifying chemical inhibitors of proteases from families other than 3CL proteases.
To determine how data on water source quality affect assessments of progress towards the 2015 Millennium Development Goal (MDG) target on access to safe drinking-water.
Data from five countries on ...whether drinking-water sources complied with World Health Organization water quality guidelines on contamination with thermotolerant coliform bacteria, arsenic, fluoride and nitrates in 2004 and 2005 were obtained from the Rapid Assessment of Drinking-Water Quality project. These data were used to adjust estimates of the proportion of the population with access to safe drinking-water at the MDG baseline in 1990 and in 2008 made by the Joint Monitoring Programme for Water Supply and Sanitation, which classified all improved sources as safe.
Taking account of data on water source quality resulted in substantially lower estimates of the percentage of the population with access to safe drinking-water in 2008 in four of the five study countries: the absolute reduction was 11% in Ethiopia, 16% in Nicaragua, 15% in Nigeria and 7% in Tajikistan. There was only a slight reduction in Jordan. Microbial contamination was more common than chemical contamination.
The criterion used by the MDG indicator to determine whether a water source is safe can lead to substantial overestimates of the population with access to safe drinking-water and, consequently, also overestimates the progress made towards the 2015 MDG target. Monitoring drinking-water supplies by recording both access to water sources and their safety would be a substantial improvement.
Summary
Background
Toluene diisocyanate (TDI) is the most important cause of occupational asthma, but the genetic mechanism of TDI‐induced asthma is still unknown.
Objective
The objective of the ...study was to identify susceptibility alleles associated with the TDI‐induced asthma phenotype.
Methods
We conducted a genome‐wide association study in 84 patients with TDI‐induced asthma and 263 unexposed healthy normal controls using Affymetrix 500K SNPchip. We also investigated the relationships between genetic polymorphisms and transcript levels in Epstein–Barr virus‐transformed lymphoblastoid cell lines from patients with TDI‐induced asthma enrolled in this study.
Results
Genetic polymorphisms of CTNNA3 (catenin alpha 3, alpha‐T catenin) were significantly associated with the TDI‐induced asthma phenotype (5.84 × 10−6 for rs10762058, 1.41 × 10−5 for rs7088181, 2.03 × 10−5 for rs4378283). Carriers with the minor haplotype, HT2 GG, of two genetic polymorphisms (rs10762058 and rs7088181) showed significantly lower PC20 methacholine level (P=0.041) and lower mRNA expression of CTNNA3 than non‐carriers (P=0.040). A genetic polymorphism in the 3′ downstream region of CTNNA3 (rs1786929), as identified by DNA direct sequencing, was significantly associated with the TDI‐induced asthma phenotype (P=0.015 in recessive analysis model) and the prevalence of serum‐specific IgG to cytokeratin 19 (P=0.031).
Conclusion
These findings suggested that multiple genetic polymorphisms of CTNNA3 may be determinants of susceptibility to TDI‐induced asthma.
In the Arctic and subarctic oceans, the relatively low supply of silicon (compared to other nutrients) can make it limiting for the growth of diatoms, a fundamental building block of the oceanic food ...web. Glaciers release large quantities of dissolved silicon and dissolvable solid amorphous silica phases into high‐latitude estuaries (fjords), but the role of these glacially‐derived silica phases in sustaining diatom growth in the coastal and open‐water sectors remains unknown. Here we show how stable and radiogenic silicon isotopes can be used together to address this question, using southwest Greenland as a case study. This study finds enhanced levels of detrital (i.e., mineral) amorphous silica, likely glacially‐sourced, sustaining a large portion of diatom growth observed off the coast, revealing how the phytoplankton community can function during high‐meltwater periods.
Plain Language Summary
Through physical grinding and chemical reactions, glaciers release a large amount of nutrients, such as silicon, from the underlying rocks. The silicon released are present in two main forms: (a) silicon dissolved in seawater, and (b) soluble silicon in glacial debris. However, there has been an ongoing debate about the contribution of this glacier‐sourced nutrient to the coastal ecosystem in the high latitudes. This is because dissolved silicon concentrations in seawater have been found at low levels in glaciated fjords and coastal environments, and the offshore transportation pathways for reactive glacial debris are poorly understood. This study aims to address these outstanding questions by employing a suite of chemical and oceanographic analyses, using southwest Greenland as a case study. We find enhanced growth of a major microalgae group at sites with high glacial debris level off the coast. Our study supports the role of glacier‐sourced nutrient in sustaining high‐latitudinal coastal ecosystem through gradual dissolution of glacial debris, especially in regions with low levels of dissolved nutrient.
Key Points
Some of the highest levels of detrital amorphous silica in the Arctic Ocean are found off a glaciated Greenland coast
Enhanced Arctic diatom production is found where detrital amorphous silica level is high, even when there is limited dissolved nutrient
Gradual dissolution of detrital amorphous silica is estimated to sustain about half of diatom production off southwest Greenland coast
The transcription factor Sox10 is a key regulator in the fate determination of a subpopulation of multipotent trunk neural crest (NC) progenitors toward glial cells instead of sensory neurons in the ...dorsal root ganglia (DRG). However, the mechanism by which Sox10 regulates glial cell fate commitment during lineage segregation remains poorly understood. In our study, we showed that the neurogenic determinant Neurogenin 2 (Neurog2) exhibited transient overlapping expression with Sox10 in avian trunk NC progenitors, which progressively underwent lineage segregation during migration toward the forming DRG. Gain- and loss-of-function studies revealed that the temporary expression of Neurog2 was due to Sox10 regulation of its protein stability. Transcriptional profiling identified Sox10-regulated F-box only protein (Fbxo9), which is an SCF (Skp1-Cul-F-box)-type ubiquitin ligase for Neurog2. Consistently, overexpression of Fbxo9 in NC progenitors down-regulated Neurog2 protein expression through ubiquitination and promoted the glial lineage at the expense of neuronal differentiation, whereas Fbxo9 knockdown resulted in the opposite phenomenon. Mechanistically, we found that Fbxo9 interacted with Neurog2 to promote its destabilization through the F-box motif. Finally, epistasis analysis further demonstrated that Fbxo9 and probably other F-box members mediated the role of Sox10 in destabilizing Neurog2 protein and directing the lineage of NC progenitors toward glial cells rather than sensory neurons. Altogether, these findings unravel a Sox10–Fbxo9 regulatory axis in promoting the glial fate of NC progenitors through Neurog2 destabilization.
Summary
The development of high throughput genotyping techniques has facilitated the identification of selection signatures of pigs. The detection of genomic selection signals in a population ...subjected to differential selection pressures may provide insights into the genes associated with economically and biologically important traits. To identify genomic regions under selection, we genotyped 488 Duroc (D) pigs and 155 D × Korean native pigs (DKNPs) using the Porcine SNP70K BeadChip. By applying the FST and extended haplotype homozygosity (EHH‐Rsb) methods, we detected genes under directional selection associated with growth/stature (DOCK7, PLCB4, HS2ST1, FBP2 and TG), carcass and meat quality (TG, COL14A1, FBXO5, NR3C1, SNX7, ARHGAP26 and DPYD), number of teats (LOC100153159 and LRRC1), pigmentation (MME) and ear morphology (SOX5), which are all mostly near or at fixation. These results could be a basis for investigating the underlying mutations associated with observed phenotypic variation. Validation using genome‐wide association analysis would also facilitate the inclusion of some of these markers in genetic evaluation programs.
Neuregulin-1 (NRG1) and its receptor ErbB4 influence several processes of neurodevelopment, but the mechanisms regulating this signalling in the mature brain are not well known. DISC1 is a ...multifunctional scaffold protein that mediates many cellular processes. Here we present a functional relationship between DISC1 and NRG1-ErbB4 signalling in mature cortical interneurons. By cell type-specific gene modulation in vitro and in vivo including in a mutant DISC1 mouse model, we demonstrate that DISC1 inhibits NRG1-induced ErbB4 activation and signalling. This effect is likely mediated by competitive inhibition of binding of ErbB4 to PSD95. Finally, we show that interneuronal DISC1 affects NRG1-ErbB4-mediated phenotypes in the fast spiking interneuron-pyramidal neuron circuit. Post-mortem brain analyses and some genetic studies have reported interneuronal deficits and involvement of the DISC1, NRG1 and ErbB4 genes in schizophrenia, respectively. Our results suggest a mechanism by which cross-talk between DISC1 and NRG1-ErbB4 signalling may contribute to these deficits.
Polymyxins remain one of the last-resort drugs to treat infections caused by MDR Gram-negative pathogens. Here, we determined the mechanisms by which chromosomally encoded resistance to colistin and ...polymyxin B can arise in the MDR uropathogenic Escherichia coli ST131 reference strain EC958.
Two complementary approaches, saturated transposon mutagenesis and spontaneous mutation induction with high concentrations of colistin and polymyxin B, were employed to select for mutations associated with resistance to polymyxins. Mutants were identified using transposon-directed insertion-site sequencing or Illumina WGS. A resistance phenotype was confirmed by MIC and further investigated using RT-PCR. Competitive growth assays were used to measure fitness cost.
A transposon insertion at nucleotide 41 of the pmrB gene (EC958pmrB41-Tn5) enhanced its transcript level, resulting in a 64- and 32-fold increased MIC of colistin and polymyxin B, respectively. Three spontaneous mutations, also located within the pmrB gene, conferred resistance to both colistin and polymyxin B with a corresponding increase in transcription of the pmrCAB genes. All three mutations incurred a fitness cost in the absence of colistin and polymyxin B.
This study identified the pmrB gene as the main chromosomal target for induction of colistin and polymyxin B resistance in E. coli.
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