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l-tryptophan is one of the eight kinds of essential amino acids for sustainable human life activity. It is common to detect the concentration of tryptophan in human serum for diagnosing and preventing brain related diseases. Herein, in this study, GCE (glassy carbon electrode) modified by Ta2O5-reduced graphene oxide (-rGO) composite (Ta2O5-rGO-GCE) is synthesized by the hydrothermal synthesis-calcination methods, which is used for detecting the concentration of tryptophan in human serum under the as-obtained optimal detection conditions. As a result, the obtained Ta2O5-rGO-GCE shows larger electrochemical activity area than other bare GCE and rGO-GCE due to the synergistic effect of Ta2O5 NPs and rGO. Meanwhile, Ta2O5-rGO-GCE shows an excellent response to tryptophan during the oxidation process in 0.1 M phosphate buffer solution (pH = 6). Moreover, three wide linear detection range (1.0–8.0 μM, 8.0–80 μM and 80–800 μM) and a low limit of detection (LOD) of 0.84 μM (S/N = 3) in the detection of tryptophan are also presented, showing the larger linear ranges and lower detection limit by employing Ta2O5-rGO-GCE. Finally, the as-proposed Ta2O5-rGO-GCE with satisfactory recoveries (101~106%) is successfully realized for the detection of tryptophan in human serum. The synthesis of Ta2O5-rGO-GCE in this article could provide a slight view for the synthesis of other electrochemical catalytic systems in detection of trace substance in human serum.

Nitrogen-doped carbon materials demonstrate high performance as electrodes in fuel cells and higher oxygen reduction reactivity than traditional Pt-based electrodes. However, the formation process of nitrogen-doped carbon materials has long been a mystery. In this study, the formation mechanism of nitrogen-doped carbon materials from polyaniline (PANI) pyrolysis was studied by the combination of in situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry (Py-VUVPI-TOF MS) and substrate-enhanced, laser-induced acoustic desorption source time-of-flight mass spectrometry (SE-LIAD-TOF MS). The initial pyrolysis species, including free radicals and intermediates, were investigated via in situ Py-VUVPI-TOF MS during the temperature-programmed desorption process (within tens of microseconds). The pyrolysis residues were collected and further investigated via SE-LIAD-TOF MS, revealing the product information of the initial pyrolysis products. The results show that the edge doping of carbon materials depends on free radical reactions rather than the direct substitution of carbon atoms by nitrogen atoms. Meanwhile, pyrrole nitrogen and pyridine nitrogen are formed by the free radical cyclization reaction and the amino aromatization reaction at the initial stage of pyrolysis, while the formation of graphitic nitrogen depends on the further polymerization reaction of pyrrole nitrogen and pyridine nitrogen.

l-tryptophan is one of the eight kinds of essential amino acids for sustainable human life activity. It is common to detect the concentration of tryptophan in human serum for diagnosing and preventing brain related diseases. Herein, in this study, GCE (glassy carbon electrode) modified by Ta O -reduced graphene oxide (-rGO) composite (Ta O -rGO-GCE) is synthesized by the hydrothermal synthesis-calcination methods, which is used for detecting the concentration of tryptophan in human serum under the as-obtained optimal detection conditions. As a result, the obtained Ta O -rGO-GCE shows larger electrochemical activity area than other bare GCE and rGO-GCE due to the synergistic effect of Ta O NPs and rGO. Meanwhile, Ta O -rGO-GCE shows an excellent response to tryptophan during the oxidation process in 0.1 M phosphate buffer solution (pH = 6). Moreover, three wide linear detection range (1.0-8.0 μM, 8.0-80 μM and 80-800 μM) and a low limit of detection (LOD) of 0.84 μM (S/N = 3) in the detection of tryptophan are also presented, showing the larger linear ranges and lower detection limit by employing Ta O -rGO-GCE. Finally, the as-proposed Ta O -rGO-GCE with satisfactory recoveries (101~106%) is successfully realized for the detection of tryptophan in human serum. The synthesis of Ta O -rGO-GCE in this article could provide a slight view for the synthesis of other electrochemical catalytic systems in detection of trace substance in human serum.

DNA methylation is a type of epigenetic modification that alters gene expression without changing the DNA sequence and mediates some cases of phenotypic plasticity. In this study, we identified six DNA methyltransferase (DNMT) genes and two methyl-CpG binding domain protein2 (MBD2) gene from Pinctada fucata martensii. We also analyzed the genome-wide DNA methylation levels of mantle edge (ME) and mantle central (MC) from P. f. martensii via methylated immunoprecipitation sequencing (MeDIP-Seq). Results revealed that both ME and MC had 122 million reads, and had 58,702 and 55,721 peaks, respectively. The obtained methylation patterns of gene elements and repeats showed that the methylation of the protein-coding genes, particularly intron and coding exons (CDSs), was more frequent than that of other genomic elements in the pearl oyster genome. We combined the methylation data with the RNA-seq data of the ME and MC of P. f. martensii and found that promoter, CDS, and intron methylation levels were positively correlated with gene expression levels except the highest gene expression level. We also identified 313 differential methylation genes (DMGs) and annotated 212 of them. These DMGs were significantly enriched in 30 pathways, such as amino acid and protein metabolism, energy metabolism, terpenoid synthesis, and immune-related pathways. This study comprehensively analyzed the methylomes of biomineralization-related tissues and helped enhance our understanding of the regulatory mechanism underlying shell formation.

We aimed to develop an oxidative-stress-activated palladium-copper nanozyme to reduce bacterial's heat sensitivity by down-regulating heat shock proteins to overcome the shortcomings of conventional photothermal antimicrobial therapy and achieve mild photothermal bactericidal efficacy.PurposeWe aimed to develop an oxidative-stress-activated palladium-copper nanozyme to reduce bacterial's heat sensitivity by down-regulating heat shock proteins to overcome the shortcomings of conventional photothermal antimicrobial therapy and achieve mild photothermal bactericidal efficacy.We first synthesized palladium-copper nanozymes (PC-NPs) by hydration and used transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy to demonstrate their successful preparation. Their photothermal therapy (PTT) and chemo-dynamic therapy (CDT) activities were then determined by a series of photothermal performance tests and peroxidase-like performance tests, and the destruction of heat shock proteins by reactive oxygen species (ROS) was verified at the protein level by Western Blotting tests, providing a basis for the effective bacteria-killing by the mild-temperature photothermal treatment subsequently applied. We also validated this promising programmed and controlled antimicrobial treatment with palladium-copper nanozymes by in vivo/in vitro antimicrobial assays. A hemolysis assay, MTT cytotoxicity test and histopathological analysis were also performed to assess the in vivo safety of PC-NPs.MethodsWe first synthesized palladium-copper nanozymes (PC-NPs) by hydration and used transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy to demonstrate their successful preparation. Their photothermal therapy (PTT) and chemo-dynamic therapy (CDT) activities were then determined by a series of photothermal performance tests and peroxidase-like performance tests, and the destruction of heat shock proteins by reactive oxygen species (ROS) was verified at the protein level by Western Blotting tests, providing a basis for the effective bacteria-killing by the mild-temperature photothermal treatment subsequently applied. We also validated this promising programmed and controlled antimicrobial treatment with palladium-copper nanozymes by in vivo/in vitro antimicrobial assays. A hemolysis assay, MTT cytotoxicity test and histopathological analysis were also performed to assess the in vivo safety of PC-NPs.In the micro-acidic environment of bacterial infection, PC-NPs showed peroxidase-like activity that broke down the H2O2 at the wound into hydroxyl radicals and down-regulated bacterial heat shock proteins. The application of PC-NPs increased bacteria's sensitivity to subsequent photothermal treatment, enabling the elimination of bacteria via mild photothermal treatment.ResultsIn the micro-acidic environment of bacterial infection, PC-NPs showed peroxidase-like activity that broke down the H2O2 at the wound into hydroxyl radicals and down-regulated bacterial heat shock proteins. The application of PC-NPs increased bacteria's sensitivity to subsequent photothermal treatment, enabling the elimination of bacteria via mild photothermal treatment.The programmed synergistic catalytic enhancement of CDT and mild photothermal therapy achieves the most efficient killing of bacteria and their biofilms, which brings future thinking in the relationship between heat shock proteins and oxidative stress damage in bacteria.ConclusionThe programmed synergistic catalytic enhancement of CDT and mild photothermal therapy achieves the most efficient killing of bacteria and their biofilms, which brings future thinking in the relationship between heat shock proteins and oxidative stress damage in bacteria.

Abnormal glucose and lipid metabolism in COVID-19 patients were recently reported with unclear mechanism. In this study, we retrospectively investigated a cohort of COVID-19 patients without pre-existing metabolic-related diseases, and found new-onset insulin resistance, hyperglycemia, and decreased HDL-C in these patients. Mechanistically, SARS-CoV-2 infection increased the expression of RE1-silencing transcription factor (REST), which modulated the expression of secreted metabolic factors including myeloperoxidase, apelin, and myostatin at the transcriptional level, resulting in the perturbation of glucose and lipid metabolism. Furthermore, several lipids, including (±)5-HETE, (±)12-HETE, propionic acid, and isobutyric acid were identified as the potential biomarkers of COVID-19-induced metabolic dysregulation, especially in insulin resistance. Taken together, our study revealed insulin resistance as the direct cause of hyperglycemia upon COVID-19, and further illustrated the underlying mechanisms, providing potential therapeutic targets for COVID-19-induced metabolic complications.

IntroductionIn the pearl culture industry, a major challenge is the overactive immunological response in pearl oysters resulting from allotransplantation, leading to shell-bead rejection and death. To better understand the molecular mechanisms of postoperative recovery and the regulatory role of DNA methylation in gene expression, we analyzed the changes in DNA methylation levels after allotransplantation in pearl oyster Pinctada fucata martensii , and elucidated the regulatory function of DNA methylation in promoter activity of nicotinic acetylcholine receptor ( nAChR ) gene.MethodsWe constructed nine DNA methylomes at different time points after allotransplantation and used bisulfite genomic sequencing PCR technology (BSP) to verify the methylation status in the promoter of nAChR . We performed Dual luciferase assays to determine the effect of the dense methylation region in the promoter on transcriptional activity and used DNA pull-down and mass spectrometry analysis to assess the capability of transcription factor binding with the dense methylation region.ResultThe DNA methylomes reveal that CG-type methylation is predominant, with a trend opposite to non-CG-type methylation. Promoters, particularly CpG island-rich regions, were less frequently methylated than gene function elements. We identified 5,679 to 7,945 differentially methylated genes (DMGs) in the gene body, and 2,146 to 3,385 DMGs in the promoter at each time point compared to the pre-grafting group. Gene ontology and pathway enrichment analyses showed that these DMGs were mainly associated with “cellular process”, “Membrane”, “Epstein-Barr virus infection”, “Notch signaling pathway”, “Fanconi anemia pathway”, and “Nucleotide excision repair”. Our study also found that the DNA methylation patterns of the promoter region of nAChR gene were consistent with the DNA methylomics data. We further demonstrated that the dense methylation region in the promoter of nAChR affects transcriptional activity, and that the methylation status in the promoter modulates the binding of different transcription factors, particularly transcriptional repressors.ConclusionThese findings enhance our understanding of the immune response and regulation mechanism induced by DNA methylation in pearl oysters after allotransplantation.

Vehicle re‐identification (Re‐ID) aims at identification of images with the same vehicle ID in a cross‐camera scenario. Prior methods mainly tend to fuse global features with local features. However, huge divergence in viewpoints among cameras leads to inconsistency of local features between query and gallery images, which causes performance drop. Recently, alignment‐based methods have been proposed to handle this problem. However, previous alignment‐based methods rely on the detection accuracy of vehicle component excessively. To solve this problem, a common visual part alignment (CVPA) model to align local features between image pairs with a few visual key points in image pairs is proposed. The main contributions of CVPA include: 1) CVPA utilizes common visual feature map generated by key points to align local features without fine‐grain annotations. 2) Using key‐point coordinates based on Gaussian smoothing can reduce the negative influence of key prediction deviation, which leads CVPA to have more flexibility and better adaptability. 3) By proposing orientation‐quadruplet loss to mine hard samples, CVPA is more robust against vehicle orientation variation. Extensive experiments show the superior performance of CVPA.

The long-time coherent integration can effectively improve the detection ability of radar targets. However, this strategy usually shows poor effect in resisting the sea clutter, which produces difficulties for accurate estimation of sea clutter characteristics and results in the inability to differentiate between the target and sea clutter. To solve this problem, a two-stage method is proposed, which consists of the sea clutter suppression stage and target decision stage. In the sea clutter suppression stage, the correlation time differences in the time and the space domains are adopted to estimate the correlation of sea clutter. Then, a selective whitening filter is proposed, which is performed more adaptively according to the estimation results. In the decision stage, the peak average ratio in the fractional Fourier domain (FRFT-PAR) is presented, which can make better use of the energy accumulation characteristics and further suppress the interference of sea clutter. Experiments on the IPIX datasets with various observation times and polarization modes are included. The results indicate that the proposed method could not only effectively suppress sea clutter but also achieve better target detection performance than baseline algorithms.

High-power single-frequency fiber lasers with diffraction-limited spots are indispensable for a wide range of photonic applications and are particularly in advanced detection and sensing technologies. However, the simultaneous achievement of kilowatt-level output power and diffraction-limited beam quality has remained elusive in all reported single-frequency fiber laser systems to date, primarily due to limitations imposed by the stimulated Brillouin scattering (SBS) effect and transverse mode instability (TMI) effect. In this study, we demonstrate the design and manufacturing of an ultra-low numerical aperture (NA) functional Yb-doped fiber featuring a bat-type refractive index distribution, specifically engineered for single-frequency laser amplification. In the fabrication, we implemented multiple chelate gas filling and particle deposition iterations, leading to an active fiber with a bat-type refractive index distribution. The unique capabilities of this large mode area and high-order modes leakage fiber (HOMLF) were demonstrated by stably amplifying the single-frequency laser with more than one kilowatt output power and near single mode beam quality (M x 2  = 1.10, M x 2  = 1.18) for the first time. This fiber design advances the leap forward in single-frequency fiber lasers, which could contribute as a novel and efficient laser amplification technique for the next generation of gravitational wave detection systems. In this study, we demonstrate the design and manufacturing of an ultra-low numerical aperture functional Yb-doped fiber featuring a bat-type refractive index distribution, specifically engineered for realizing kilowatt single-frequency laser.