Achieving high carrier separation over Bi4O5I2through Ni doping for improved photocatalytic CO2reduction.

Photocatalytic CO2reduction is considered to be an appealing way of alleviating environmental pollution and energy shortages simultaneously under mild condition. However, the activity is greatly limited by the poor separation of the photogenerated carriers. Ion doping is a feasible strategy to facilitate the charge transfer. In this work, Ni-doped Bi4O5I2photocatalyst is successfully fabricated using a one-pot hydrothermal method. A few doping levels appear in the energy band of Bi4O5I2after Ni doping, which are used as springboards for electrons transition, thus promoting photoexcited electrons and holes separation. As a consequence, a remarkably enhanced yield of CO and CH4(6.2 and 1.9µmol g-1h-1) is obtained over the optimized Bi4O5I2-Ni15, which is approximately 2.1 and 3.8 times superior to pure Bi4O5I2, respectively. This work may serve as a model for the subsequent research of Bi-based photocatalysts to implement high-performance CO2photoreduction.

Coenzyme-Mediated Electro-RAFT Polymerization for Amplified Electrochemical Interrogation of Trypsin Activity.

Trypsin is a key proteolytic enzyme in the digestive system and its abnormal levels are indicative of some pancreatic diseases. Taking advantage of the coenzyme-mediated electrografting of ferrocenyl polymers as a novel strategy for signal amplification, herein, a signal-on cleavage-based electrochemical biosensor is reported for the highly selective interrogation of trypsin activity at ultralow levels. The construction of the trypsin biosensor involves (i) the immobilization of peptide substrates (without free carboxyl groups) via the N-terminus, (ii) the tryptic cleavage of peptide substrates, (iii) the site-specific labeling of the reversible addition-fragmentation chain transfer (RAFT) agents, and (iv) the grafting of ferrocenyl polymers through the electro-RAFT (eRAFT) polymerization, which is mediated by potentiostatic reduction of nicotinamide adenine dinucleotide (NAD+) coenzymes. Through the NAD+-mediated eRAFT (NAD+-eRAFT) polymerization of ferrocenylmethyl methacrylate (FcMMA), the presence of a few tryptic cleavage events can eventually result in the recruitment of a considerable amount of ferrocene redox tags. Obviously, the NAD+-eRAFT polymerization is low-cost and easy to operate as a highly efficient strategy for signal amplification. As expected, the as-constructed biosensor is highly selective and sensitive toward the signal-on interrogation of trypsin activity. Under optimal conditions, the detection limit can be as low as 18.2 µU/mL (∼72.8 pg/mL). The results also demonstrate that the as-constructed electrochemical trypsin biosensor is applicable to inhibitor screening and the interrogation of enzyme activity in the presence of complex sample matrices. Moreover, it is low-cost, less susceptible to false-positive results, and relatively easy to fabricate, thus holding great potential in diagnostic and therapeutic applications.

Uncertainty-Aware Active Domain Adaptive Salient Object Detection.

Due to the advancement of deep learning, the performance of salient object detection (SOD) has been significantly improved. However, deep learning-based techniques require a sizable amount of pixel-wise annotations. To relieve the burden of data annotation, a variety of deep weakly-supervised and unsupervised SOD methods have been proposed, yet the performance gap between them and fully supervised methods remains significant. In this paper, we propose a novel, cost-efficient salient object detection framework, which can adapt models from synthetic data to real-world data with the help of a limited number of actively selected annotations. Specifically, we first construct a synthetic SOD dataset by copying and pasting foreground objects into pure background images. With the masks of foreground objects taken as the ground-truth saliency maps, this dataset can be used for training the SOD model initially. However, due to the large domain gap between synthetic images and real-world images, the performance of the initially trained model on the real-world images is deficient. To transfer the model from the synthetic dataset to the real-world datasets, we further design an uncertainty-aware active domain adaptive algorithm to generate labels for the real-world target images. The prediction variances against data augmentations are utilized to calculate the superpixel-level uncertainty values. For those superpixels with relatively low uncertainty, we directly generate pseudo labels according to the network predictions. Meanwhile, we select a few superpixels with high uncertainty scores and assign labels to them manually. This labeling strategy is capable of generating high-quality labels without incurring too much annotation cost. Experimental results on six benchmark SOD datasets demonstrate that our method outperforms the existing state-of-the-art weakly-supervised and unsupervised SOD methods and is even comparable to the fully supervised ones. Code will be released at: https://github.com/czh-3/UADA.

Bioinspired Electro-RAFT Polymerization for Electrochemical Sensing of Nucleic Acids.

Sensing of ultralow-abundance nucleic acids (NAs) is integral to medical diagnostics and pathogen screening. We present herein an electrochemical method for the highly selective and amplified sensing of NAs, using a peptide nucleic acid (PNA) recognition probe and a bioinspired electro-RAFT polymerization (BERP)-based amplification strategy. The presented method is based on the recognition of target NAs by end-tethered PNA probes, the labeling of thiocarbonylthio reversible addition-fragmentation chain transfer (RAFT) agents, and the BERP-assisted growth of ferrocenyl polymers. The dynamic growth of polymers is electrochemically regulated by the reduction of 1-methylnicotinamide (MNA) organic cations, the redox center of nicotinamide adenine dinucleotide (NAD+, coenzyme I). Specifically, electroreduction of the MNA cations causes the fragmentation of thiocarbonylthio RAFT agents into radical species, triggering the polymerization of ferrocenyl monomers, thereby recruiting plenty of ferrocene electroactive tags for amplified sensing. It is obvious that the BERP-based strategy is inexpensive and simple in operation. Benefiting from the high specificity of the PNA recognition probe and the amplified signal by the BERP-based strategy, this method is highly selective and the detection limit is as low as 0.58 fM (S/N = 3). Besides, it is applicable to the sensing of NAs in serum samples, thus showing great promise in the selective and amplified sensing of NAs.

Impact of adding glucose-coated water-soluble silver nanoparticles to the silkworm larval diet on silk protein synthesis and related properties.

Biological modifications of the silk fibroin (silk) material have broad applications in textiles, biomedical materials and other industrial materials. It is economical to incorporate nanoparticles to the biosynthesis of silk fibroin by adding them to silkworm larval diets. This strategy may result in the rapid stable production of modified silk. Glucose-coated silver nanoparticles (AgNPs) were used to improve the AgNPs' biocompatibility, and the AgNPs were efficiently incorporated into silk by feeding. Larvae fed with AgNPs produced silk with significantly improved antibacterial properties and altered silk secondary structures. Both positive and negative effects on the growth and synthesis of silk proteins were observed after different AgNPs doses. Larvae feeding with low concentration of 0.02% and medium 0.20% AgNPs have greater transfer efficiencies of AgNPs to silk compared with feeding high concentration of 2.00% AgNPs. In addition, the elongation and tensile strength of the produced silk fibers were also significantly increased, with greater mammalian cell compatibility. The appropriate AgNPs concentration in the diet of silkworms can promote the synthesis of silk proteins, enhance their mechanical properties, improve their antibacterial property and inhibit the presence of Gram-negative bacteria.

Differences in gut microbiota between silkworms (Bombyx mori) reared on fresh mulberry (Morus alba var. multicaulis) leaves or an artificial diet.

Artificial diets for silkworms have many potential applications and they are important in sericulture. However, the challenges of weak larvae and low silk protein synthesis efficiency in silkworms reared on artificial diets have not been resolved. Here, we used high-throughput sequencing to analyse the differences between the gut microbiota of 5th-instar larvae reared on mulberry leaves and larvae reared on an artificial diet. The results showed that at the phylum level, Cyanobacteria, Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria are the dominant bacteria in the intestines of silkworm larvae of all the strains. But the abundance of dominant bacteria in the gut microbiota differed between the silkworm strains that were reared on mulberry leaves, as well as between the silkworm strains that were reared on the artificial diet, while the gut microbiota diversity was lower in the silkworm strains that were reared on the artificial diet. Prediction of the functions of the gut microbiota in the hosts indicated that there was no significant difference between the silkworm strains that were reared on mulberry leaves, while there were significant differences between silkworm strains reared on the artificial diet. When the silkworm diet changed from mulberry leaves to the artificial diet, changes in gut microbiota in the silkworms affected host nutrient metabolism and immune resistance. These changes may be related to the adaptation of silkworms to their long evolutionary history of eating mulberry leaves.

Metabolomics differences between silkworms (Bombyx mori) reared on fresh mulberry (Morus) leaves or artificial diets.

Silkworms (Bombyx mori) reared on artificial diets have great potential applications in sericulture. However, the mechanisms underlying the enhancement of metabolic utilization by altering silkworm nutrition are unclear. The aim of this study was to investigate the mechanisms responsible for the poor development and low silk protein synthesis efficiency of silkworms fed artificial diets. After multi-generational selection of the ingestive behavior of silkworms to artificial diets, we obtained two strains, one of which developed well and another in which almost all its larvae starved to death on the artificial diets. Subsequently, we analyzed the metabolomics of larval hemolymph by gas chromatography/liquid chromatography-mass spectrometry, and the results showed that vitamins were in critically short supply, whereas the nitrogen metabolic end product of urea and uric acid were enriched substantially, in the hemolymph of the silkworms reared on the artificial diets. Meanwhile, amino acid metabolic disorders, as well as downregulation of carbohydrate metabolism, energy metabolism, and lipid metabolism, co-occurred. Furthermore, 10 male-dominant metabolites and 27 diet-related metabolites that differed between male and female silkworms were identified. These findings provide important insights into the regulation of silkworm metabolism and silk protein synthesis when silkworms adapt to an artificial diet.

Identification of nitrosamine precursors from urban drainage during storm events: A case study in southern China.

The drinking water sources of many cities in southern China are frequently contaminated by upstream urban drainage during storm events, which brings high concentrations of N-nitrosamine (NA) precursors and poses a threat to the safety of drinking water. We conducted two sampling campaigns during the heavy rain season in 2015 in one representative city in southern China. We detected that the concentration of N-nitrosodimethylamine formation potential (NDMA FP) in urban drainage during two storm events was 80-115 ng/L and the total formation potential concentration of nine nitrosamines (TNA9 FP) was 145-165 ng/L. To address the deteriorated water quality, 30 mg/L of powdered activated carbon (PAC) was fed into the water intake. PAC adsorption alone could remove 52% of NDMA FP and 52% of TNA FP, while the subsequent conventional process only removed 8% of TNA FP. We isolated six chemicals (N,N-benzyldimethylamine, 5-[(dimethylamino)methyl]-2-furanmethanol, N,N-dimethyl-3-aminophenol, N,N-dimethylethylamine, Ziram, and N,N-dimethylaniline) and confirmed them to be NA precursors. Among these NA precursors, Ziram was identified for the first time as a NA precursor that is formed via chloramination; its molar yield for NDMA was 6.73 ± 0.40%.