Cep131-Cep162 and Cby-Fam92 complexes cooperatively maintain Cep290 at the basal body and contribute to ciliogenesis initiation.

Cilia play critical roles in cell signal transduction and organ development. Defects in cilia function result in a variety of genetic disorders. Cep290 is an evolutionarily conserved ciliopathy protein that bridges the ciliary membrane and axoneme at the basal body (BB) and plays critical roles in the initiation of ciliogenesis and TZ assembly. How Cep290 is maintained at BB and whether axonemal and ciliary membrane localized cues converge to determine the localization of Cep290 remain unknown. Here, we report that the Cep131-Cep162 module near the axoneme and the Cby-Fam92 module close to the membrane synergistically control the BB localization of Cep290 and the subsequent initiation of ciliogenesis in Drosophila. Concurrent deletion of any protein of the Cep131-Cep162 module and of the Cby-Fam92 module leads to a complete loss of Cep290 from BB and blocks ciliogenesis at its initiation stage. Our results reveal that the first step of ciliogenesis strictly depends on cooperative and retroactive interactions between Cep131-Cep162, Cby-Fam92 and Cep290, which may contribute to the complex pathogenesis of Cep290-related ciliopathies.

Monomeric Far-red and Near-infrared Fluorescent Biliproteins of Ultrahigh Brightness.

Far-red and near-infrared fluorescent proteins have regions of maximum transmission in most tissues and can be widely used as fluorescent biomarkers. We report that fluorescent phycobiliproteins originating from the phycobilisome core subunit ApcF2 can covalently bind biliverdin, named BDFPs. To further improve BDFPs, we conducted a series of studies. Firstly, we mutated K53Q and T144A of BDFPs to increase their effective brightness up to 190 % in vivo. Secondly, by homochromatic tandem fusion of high-brightness BDFPs to achieve monomerization, which increases the effective brightness by up to 180 % in vivo, and can effectively improve the labeling effect. By combining the above two approaches, the brightness of the tandem BDFPs was much improved compared with that of the previously reported fluorescent proteins in a similar spectral range. The tandem BDFPs were expressed stably while maintaining fluorescence in mammalian cells and Caenorhabditis elegans. They were also photostable and resistant to high temperature, low pH, and chemical denaturation. The tandem BDFPs advantages were proved in applications as biomarkers for imaging in super-resolution microscopy.

Chromosome-level reference genome and resequencing of 322 accessions reveal evolution, genomic imprint and key agronomic traits in adzuki bean.

Adzuki bean (Vigna angularis) is an important legume crop cultivated in over 30 countries worldwide. We developed a high-quality chromosome-level reference genome of adzuki bean cultivar Jingnong6 by combining PacBio Sequel long-read sequencing with short-read and Hi-C technologies. The assembled genome covers 97.8% of the adzuki bean genome with a contig N50 of approximately 16 Mb and a total of 32 738 protein-coding genes. We also generated a comprehensive genome variation map of adzuki bean by whole-genome resequencing (WGRS) of 322 diverse adzuki beans accessions including both wild and cultivated. Furthermore, we have conducted comparative genomics and a genome-wide association study (GWAS) on key agricultural traits to investigate the evolution and domestication. GWAS identified several candidate genes, including VaCycA3;1, VaHB15, VaANR1 and VaBm, that exhibited significant associations with domestication traits. Furthermore, we conducted functional analyses on the roles of VaANR1 and VaBm in regulating seed coat colour. We provided evidence for the highest genetic diversity of wild adzuki (Vigna angularis var. nipponensis) in China with the presence of the most original wild adzuki bean, and the occurrence of domestication process facilitating transition from wild to cultigen. The present study elucidates the genetic basis of adzuki bean domestication traits and provides crucial genomic resources to support future breeding efforts in adzuki bean.

Visible-Light-Promoted Cascade Coupling of 2-Isocyanonaphthalenes with Elemental Sulfur and Amines to Construct Naphtho[2,1-d]thiazol-2-Amines.

A visible-light-induced strategy has been explored for the synthesis of naphtho[2,1-d]thiazol-2-amines through ortho-C-H sulfuration of 2-isocyanonaphthalenes with elemental sulfur and amines under external photocatalyst-free conditions. This three-component reaction, which utilizes elemental sulfur as the odorless sulfur source, molecular oxygen as the clean oxidant, and visible light as the clean energy source, provides a mild and efficient approach to construct a series of naphtho[2,1-d]thiazol-2-amines. Preliminary mechanistic studies indicated that visible-light-promoted photoexcitation of reaction intermediates consisting of thioureas and DBU might be involved in this transformation.

Light-Driven Access to Selenium-Substituted Thiazole-2-imine Derivatives.

The thiazole-2-imine derivatives with interesting pharmacological activities have attracted significant attention. However, previously reported synthesis strategies usually suffered from some drawbacks, such as the use of metals/additive and harsh reaction conditions. Herein, we developed a metal- and photoinitiator-free photocatalytic strategy for the synthesis of various selenium-substituted thiazole-2-imine derivatives for the first time. The reaction displayed mild reaction conditions, simple operation, a broad substrate scope (37 examples), and good to excellent yields.

Structure optimization of Cmpd-15 as negative allosteric modulators for the ß2-adrenergic receptor.

19 derivatives of 1-benzyl-3-arylpyrazole-5-carboxamides (H1-H19) and 5 derivatives of 1-benzyl-5-arylpyrazole-3-carboxamides (J1-J5) have been designed and synthesized as potential negative allosteric modulators (NAMs) for the ß2-adrenergic receptor (ß2AR). The new pyrazole derivatives were screened on the classic G-protein dependent signaling pathway at ß2AR. The majority of 1-benzyl-3-aryl-pyrazole-5-carboxamide derivatives show more potent allosteric antagonistic activity against ß2AR than Cmpd-15, the first reported ß2AR NAM. However, the 1-benzyl-5-arylpyrazole-3-carboxamide derivatives exhibit very poor or even no allosteric antagonistic activity for ß2AR. Furthermore, the active pyrazole derivatives have relative better drug-like profiles than Cmpd-15. Taken together, we discovered a series of derivatives of 1-benzyl-3-arylpyrazole-5-carboxamides as a novel scaffold of ß2AR NAM.

A Chemiluminescence Sensor for the Detection of α-Fetoprotein and Carcinoembryonic Antigen Based on Dual-Aptamer Functionalized Magnetic Silicon Composite.

In this work, a dual-aptamer functionalized magnetic silicon composite was prepared and used to construct a chemiluminescence (CL) sensor for the detection of α-fetoprotein (AFP) and carcinoembryonic antigen (CEA). First, SiO2@Fe3O4 was prepared, and polydiallyl dimethylammonium chloride (PDDA) and AuNPs were sequentially loaded on SiO2@Fe3O4. Subsequently, the complementary strand of CEA aptamer (cDNA2) and the aptamer of AFP (Apt1) were attached to AuNPs/PDDA-SiO2@Fe3O4. Then, the aptamer of CEA (Apt2) and G quadruplex peroxide-mimicking enzyme (G-DNAzyme) were sequentially connected to cDNA2, leading to the final composite. Then, the composite was used to construct a CL sensor. When AFP is present, it will combine with Apt1 on the composite to hinder the catalytic ability of AuNPs to luminol-H2O2, achieving AFP detection. When CEA is present, it will recognize and bind with Apt2, so G-DNAzyme is released to solution and catalyzes the reaction of luminol-H2O2 to achieve CEA determination. After the application of the prepared composite, AFP and CEA were detected in the magnetic medium and supernatant, respectively, after simple magnetic separation. Therefore, the detection of multiple liver cancer markers is realized through the CL technology without additional instruments or technology, which broadens the application range of CL technology. The sensor for detecting AFP and CEA shows wide linear ranges of 1.0 × 10-4 to 1.0 ng·mL-1 and 0.0001-0.5 ng·mL-1 and low detection limits of 6.7 × 10-5 ng·mL-1 and 3.2 × 10-5 ng·mL-1, respectively. Finally, the sensor was successfully used to detect CEA and AFP in serum samples and provides great potential for detection of multiple liver cancer markers in early clinical diagnosis.

Roles of gut microbiota in atrial fibrillation: insights from Mendelian randomization analysis and genetic data from over 430,000 cohort study participants.

BACKGROUND: Gut microbiota imbalances have been suggested as a contributing factor to atrial fibrillation (AF), but the causal relationship is not fully understood. OBJECTIVES: To explore the causal relationships between the gut microbiota and AF using Mendelian randomization (MR) analysis. METHODS: Summary statistics were from genome-wide association studies (GWAS) of 207 gut microbial taxa (5 phyla, 10 classes, 13 orders, 26 families, 48 genera, and 105 species) (the Dutch Microbiome Project) and two large meta-GWASs of AF. The significant results were validated in FinnGen cohort and over 430,000 UK Biobank participants. Mediation MR analyses were conducted for AF risk factors, including type 2 diabetes, coronary artery disease (CAD), body mass index (BMI), blood lipids, blood pressure, and obstructive sleep apnea, to explore the potential mediation effect of these risk factors in between the gut microbiota and AF. RESULTS: Two microbial taxa causally associated with AF: species Eubacterium ramulus (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.04-1.12, P = 0.0001, false discovery rate (FDR) adjusted p-value = 0.023) and genus Holdemania (OR 1.15, 95% CI 1.07-1.25, P = 0.0004, FDR adjusted p-value = 0.042). Genus Holdemania was associated with incident AF risk in the UK Biobank. The proportion of mediation effect of species Eubacterium ramulus via CAD was 8.05% (95% CI 1.73% - 14.95%, P = 0.008), while the proportion of genus Holdemania on AF via BMI was 12.01% (95% CI 5.17% - 19.39%, P = 0.0005). CONCLUSIONS: This study provided genetic evidence to support a potential causal mechanism between gut microbiota and AF and suggested the mediation role of AF risk factors.

Effect of ibuprofen (IBU) on the sulfur-based and calcined pyrite-based autotrophic denitrification (SCPAD) systems with two filling modes: Performance and toxic response mechanism.

To investigate the effect of ibuprofen (IBU) on the sulfur-based and calcined pyrite-based autotrophic denitrification (SCPAD) systems, two individual reactors with the layered filling (L-SCPAD) and mixed filling (M-SCPAD) systems were established via sulfur and calcined pyrite. Effluent NO3--N concentration of the L-SCPAD and M-SCPAD systems was first increased to 6.44, 0.93 mg/L under 0.5 mg/L IBU exposure and gradually decreased to 1.66 mg/L, 0 mg/L under 4.0 mg/L IBU exposure, indicating that NO3--N removal performance of the M-SCPAD system was better than that of the L-SCPAD system. The variation of extracellular polymeric substances (EPS) characteristics demonstrated that more EPS was secreted in the M-SCPAD system compared to the L-SCPAD system, which contributed to forming a more stable biofilm structure and protecting microorganisms against the toxicity of IBU in the M-SCPAD system. Moreover, the increased electron transfer impedance and decreased cytochrome c implied that IBU inhibited the electron transfer efficiency of the L-SCPAD and M-SCPAD systems. The decreased adenosine triphosphate (ATP) and electron transfer system activity (ETSA) content showed that IBU inhibited metabolic activity, but the M-SCPAD system exhibited higher metabolic activity compared to the L-SCPAD system. In addition, the analysis of the bacterial community indicated a more stable abundance of nitrogen removal function bacteria (Bacillus) in the M-SCPAD system compared to the L-SCPAD system, which was conducive to maintaining a stable denitrification performance. The toxic response mechanism based on the biogeobattery effect was proposed in the SCPAD systems under IBU exposure. This study provided an important reference for the long-term toxic effect of IBU on the SCPAD systems.

Early vascular changes after silicone oil removal using optical coherence tomography angiography.

BACKGROUND: This study evaluated the vascular changes in the macular and peripapillary regions before and after silicone oil (SO) removal in patients with rhegmatogenous retinal detachment. METHODS: This single-center case series assessed patients who underwent SO removal at one hospital. Patients who underwent pars plana vitrectomy and perfluoropropane gas tamponade (PPV + C3F8) were selected as controls. Superficial vessel density (SVD) and superficial perfusion density (SPD) in the macular and peripapillary regions were assessed by optical coherence tomography angiography (OCTA). Best-corrected visual acuity (BCVA) was assessed using LogMAR. RESULTS: Fifty eyes were administered SO tamponade, 54 SO tamponade(SOT) contralateral eyes, 29 PPV + C3F8 eyes, and 27 PPV + C3F8 contralateral eyes were selected. SVD and SPD in the macular region were lower in eyes administered SO tamponade compared with SOT contralateral eyes (P < 0.01). Except for the central area, SVD and SPD in the other areas of the peripapillary region were reduced after SO tamponade without SO removal (P < 0.01). No significant differences were found in SVD and SPD between PPV + C3F8 contralateral and PPV + C3F8 eyes. After SO removal, macular SVD and SPD showed significant improvements compared with preoperative values, but no improvements in SVD and SPD were observed in the peripapillary region. BCVA (LogMAR) decreased post-operation and was negatively correlated with macular SVD and SPD. CONCLUSIONS: SVD and SPD are decreased during SO tamponade and increased in the macular region of eyes that underwent SO removal, suggesting a possible mechanism for reduced visual acuity during or after SO tamponade. TRIAL REGISTRATION: Registration date: 22/05/2019; Registration number, ChiCTR1900023322; Registration site, Chinese Clinical Trial Registry (ChiCTR).

Responses of anammox and sulfur/pyrite autotrophic denitrification in one-stage system to high nitrogen load: Performance, metabolic and bacterial community.

To remove residual nitrate from anammox process and achieve efficient nitrogen removal, a two-stage system (TAS) with the two individual reactors and a one-stage system (OAS) with the spatial functional areas in one reactor were established via anammox coupling sulfur autotrophic denitrification. The total nitrogen removal efficiency (TNRE) of OAS system (97.85 ± 1.92%) was higher than that of TAS system (93.63 ± 1.87%) under the influent NH4+-N and NO2--N of 227 and 300 mg/L. Meanwhile, the responses of microbial metabolism to high nitrogen load were investigated in term of microbial metabolites, electron transfer and metabolic activity. Microbial metabolites characteristics demonstrated that the OAS system secreted more EPS with lower protein (PN)/polysaccharide (PS) ratio than that in the TAS system, which was beneficial to protect bacteria from high nitrogen load. Electrochemical analysis suggested that the secretion of electron conductive substance (such as PN, PS) and redox active substances (such as flavin mononucleotide, the binding of flavins and cytochrome c on the outer membrane) were increased in the OAS system, which promoted the electron transfer efficiency. Moreover, the electron transport system activity (ETSA) values and ATP contents in OAS system were higher than that in the TAS system, which indicated that metabolic activity was improved in OAS system under the stimulation of high nitrogen load. Additionally, the bacterial community analysis indicated that the functional bacteria of Candidatus_Kuenenia and Armatimonadetes_gp5 had higher abundance in the OAS system than that in the TAS system, which was beneficial to realize the stable nitrogen removal performance. Overall, the responses mechanism of the OAS system was established to explain the resistant to high nitrogen load.

Hemin as a General Static Dark Quencher for Constructing Heme Oxygenase-1 Fluorescent Probes.

The development of small-molecule probes suitable for live-cell applications remains challenging yet highly desirable. We report the first fluorescent probe, RBH, for imaging the heme oxygenase-1 (HO-1) activity in live cells after discovering hemin as a universal dark quencher. Hemin works via a static quenching mechanism and shows high quenching efficiency (>97 %) with fluorophores across a broad spectrum (λex =400-700 nm). The favorable properties of RBH (e.g. long excitation/emission wavelengths, fast response rate and high magnitude of signal increase) enable its use for determining HO-1 activity in complex biological samples. As HO-1 is involved in regulating antioxidant defence, iron homeostasis and gasotransmitter carbon monoxide production, we expect RBH to be a powerful tool for dissecting its functions. Also, the discovery of hemin as a general static dark quencher provides a straightforward strategy for constructing novel fluorescent probes for diverse biological species.

New Far-Red and Near-Infrared Fluorescent Phycobiliproteins with Excellent Brightness and Photostability.

Far-red and near-infrared fluorescent proteins can be used as fluorescence biomarkers in the region of maximal transmission of most tissues and facilitate multiplexing. Recently, we reported the generation and properties of far-red and near-infrared fluorescent phycobiliproteins, termed BeiDou Fluorescent Proteins (BDFPs), which can covalently bind the more readily accessible biliverdin. Far-red BDFPs maximally fluoresce at ∼670 nm, while near-infrared BDFPs fluoresce at ∼710 nm. In this work, we molecularly evolved BDFPs as follows: (a) mutations L58Q, S68R and M81K of BDFPs, which can maximally enhance the effective brightness in vivo by 350 %; (b) minimization and monomerization of far-red BDFPs 2.1, 2.2, 2.3, and near-infrared BDFPs 2.4, 2.5 and 2.6. These newly developed BDFPs are remarkably brighter than the formerly reported far-red and near-infrared fluorescent proteins. Their advantages are demonstrated by biolabeling in mammalian cells using super-resolution microscopy.

Hispolon alleviates oxidative damage by stimulating the Nrf2 signaling pathway in PC12 cells.

Natural products derived from the daily diet are garnering increasing attention for neurodegenerative disease (ND) treatment. Hispolon (His), a small molecule from Phellinus linteus, has been reported to have various pharmacological activities. Here, we evaluated its protective effect on a neuron-like rat pheochromocytoma cell line (PC12). Results showed that His could restore cell death induced by oxidative damage. Nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) plays a significant role in maintaining cellular redox homeostasis. After treatment with His, some Nrf2-governed antioxidant genes were upregulated in a dose-dependent manner. However, the protective effect of His on PC12 cells was easily terminated by Nrf2 knockdown, demonstrating that Nrf2 is a critical component in this cytoprotective process. Taken together, our study showed that His was not only an effective activator of Nrf2 but also a promising candidate for ND treatment.

A chemiluminescence aptasensor for sensitive detection of alpha-fetoprotein based on hemin@ZIF-67.

In this work, hemin@ZIF-67 composites were prepared and were used to construct a chemiluminescence (CL) aptasensor for alpha-fetoprotein (AFP) detection. Hemin is a catalytic porphyrin with two carboxylate groups that can covalently bond to metal ions. A hemin/ZIF-67 composite was prepared via covalent bonding between the carboxyl groups of hemin and the cobalt ion of ZIF-67, and these materials were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), and X-ray diffraction (XRD). Hemin@ZIF-67 was used as the peroxidase material, and the aptamer of alpha-fetoprotein was modified on its surface by electrostatic adsorption. Then a simple CL aptasensor was constructed based on the CL system of luminol-H2O2-NaOH. Under the optimal conditions, the CL intensity value was linearly proportional to the concentration of AFP in the range of 4 × 10-10 to 200 × 10-10 mg/mL. The detection limit was 1.3 × 10-10 mg/mL. Thus the aptasensor enables highly sensitive and selective detection of AFP.

Effects of different carbon sources on the efficiency of sulfur-oxidizing denitrifying microorganisms.

This study aims to compare the effects of different carbon sources on sulfur-oxidizing denitrifying microorganisms by using glucose, ethanol, and acetate as carbon sources. Under the same chemical oxygen demand Cr (CODCr), nitrate, and sulfide concentrations, the removal rate of nitrate and total organic carbon, and the yield of elemental sulfur in a static experiment and a continuous flow reactor with glucose as the carbon source were lower than those with ethanol and acetic acid as the carbon source. The core sulfur-oxidizing denitrifying bacteria that use glucose as the carbon source were Azoarcus, Geoalkalibacter, and Mangroviflexus; those that use ethanol as the carbon source were Arcobacter, Pseudomonas, and Thauera; those that use acetate as the carbon source were Pseudomonas and Azoarcus. The metabolic activity of microorganisms that use different carbon sources was explained by functional gene detection. The fluctuation of gltA, a functional gene indicating heterotrophic metabolism of microorganisms, was small in three reactors, but that of the sulfur oxidation gene, Sqr, in the reactor with acetic acid as the carbon source was larger. Our results suggest that acetate is a more suitable carbon source for denitrification-desulfurization systems.

Bio-augmentation of the filler-enhanced denitrifying sulfide removal process in expanded granular sludge bed reactors.

Sulfur- and nitrogen-containing organic industrial wastewaters, which primarily result from several processes, including pharmaceutical, slaughter, papermaking, and petrochemical processes, are typical examples of refractory wastewaters. To ensure resource utilization, sulfur compounds at high concentrations in such wastewaters can be converted to elemental sulfur through specific methods. Specifically, the denitrifying sulfide removal (DSR) process can be employed to effectively recover elemental sulfur via biological sulfide oxidation, and reportedly, bio-augmentation presents as an effective strategy by which the challenges that limit the application of the DSR process can be overcome. However, the bacterial loss resulting from microorganism activity inhibition owing to toxic effect of high sulfide concentration as well as the complexity of the organic matter (carbon source) in actual wastewater environments reduce the actual elemental sulfur production rate. In this regard, the bio-augmentation effect of adding fillers under complex carbon source conditions was studied. The structure and function of the microbial community on the surface of the fillers were also analysed to reveal the internal factors that contributed to the increased efficiency of elemental sulfur generation. The results obtained showed that relative to the control, elemental sulfur generation increased 1.5- and 2-fold following the addition of fillers and fillers with microbial inoculants, respectively. Further, in the reactor with the added filler, the dominant bacteria in the biofilm on the filler surface were Pseudomonas and Azoarcus, while in reactor with added fillers plus microbial inoculates, the dominant bacteria in the biofilm on the filler surface were Pseudomonas and Arcobacter. These findings indicated that bio-augmentation promoted the expression of sulfur oxidation functional genes. Furthermore, adding Pseudomonas sp. gs1 for bio-augmentation improved the impact load resistance of the biofilm on the surface of the filler, leading to the rapid restoration of the elemental sulfur generation rate after the impact.

Rapid start of high-concentration denitrification and desulfurization reactors by heterotrophic denitrification sulphur-oxidising bacteria.

High sulphide concentrations can be toxic to denitrifying and desulphurising microorganisms. In this study, bioaugmentation was used to solve this problem. Pseudomonas sp. gs1 can tolerate 400 mg/L sulphide and converts most of the sulphide into elemental sulphur after 4 h. A solid inoculum of Pseudomonas sp. h1 was prepared. Two reactors, that is, one with and one without inoculum, were simultaneously run for 60 days. Bioreactor II to which bacterial inoculum was added reached a good treatment performance on day 3. The elemental sulphur concentration of the effluent was 342.6 mg/L. It was maintained at 245.3-333.8 mg/L during the subsequent operation. In contrast, reactor I without inoculants achieved the same performance on day 50. High-throughput sequencing shows that Pseudomonas and Azoarcus are the dominant genera. The abundance of the genus Pseudomonas and related denitrifying sulphur-oxidising bacteria in reactor I increases with the operation time. This phenomenon was confirmed by testing the sqr and gltA genes. The quantitative fluorescence PCR test also proves that the addition of bacteria leads to a rapid increase in the sulphur oxidation and carbon metabolism of the activated sludge in the reactor.

Enhanced simultaneous partial nitrification and denitrification performance of aerobic granular sludge via tapered aeration in sequencing batch reactor for treating low strength and low COD/TN ratio municipal wastewater.

The aerobic granular sludge simultaneous partial nitrification, denitrification and phosphorus removal (AGS-SPNDPR) process was carried out via tapered aeration in sequencing batch reactor (SBR) for treating low strength and low COD/TN ratio municipal wastewater. The results showed that aerobic granular sludge was successfully cultivated with good sedimentation performance when treating the municipal wastewater. Meanwhile, the median granule size increased to 270 (R1) and 257 (R2) µm on day 80. The excellent removal performance of COD (92%) and NH4+-N (95%) were achieved under different aeration modes, while the higher TN removal efficiency (76%) was achieved by tapered aeration. The accumulation of NO2--N in R2 indicated that the tapered aeration was beneficial to achieve simultaneously partial nitrification and denitrification. Meanwhile, the high-efficiency phosphorus (95%) removal was realized via additional carbon source, and SPNDPR process was formed under tapered aeration. The bacterial community analysis indicated denitrifying glycogen-accumulating organisms (DGAOs) Candidatus_Competibacter and ammonia-oxidizing bacteria (AOB) Nitrosomonas were more effectively enriched via tapered aeration, while phosphorus-accumulating organisms (PAOs) Candidatus_Accumulibacter were effectively enriched under additional organic carbon. AOB, denitrifying bacteria and PAOs were simultaneously enriched by tapered aeration and additional carbon source, which was beneficial to nutrients removal. This study might be conducive to the application of AGS-SPNDPR system for treating low strength and low COD/TN ratio municipal wastewater under tapered aeration.

Rational design of biogenic PdxAuy nanoparticles with enhanced catalytic performance for electrocatalysis and azo dyes degradation.

The green biogenic PdAu nanoparticles (bio-PdAu NPs) exhibits remarkable catalytic performance in hydrogenation, which is highly desired. However, the catalytic principles and effectiveness of bio-PdxAuy NPs in response to various catalytic systems (electrocatalysis and suspension-catalysis) are unclear. Herein, a facile synthetic strategy for bio-PdxAuy NPs synthesis with controlled size and the catalytic principles for hydrogen evolution reaction (HER) and azo dye degradation is reported. In the biosynthetic process, the size and composition of the bio-PdxAuy NPs could be precisely controlled by predesigning the precursor mass ratio of Pd/Au, and the Au proportion showed a linear relationship with the size of NPs (R2 = 0.92). The obtained bio-PdxAuy NPs exhibit variable activity in electrocatalysis (HER) and suspension-catalysis (azo dye degradation). For electrocatalysis, the formation of conductive networks that facilitates the extracellular electron transfer is crucial. It was revealed that the bio-Pd2Au8 exhibited superior electrocatalytic performance in HER/toward hydrogen evolution, with a maximum current density of 1.65 mA cm-2, which was 1.54 times higher than that commercial Pd/C (1.07 mA cm-2). The high electrocatalytic activity was attributed to its appropriate size (81.38 ± 6.14 nm) and uniform distribution on the cell surface, which promoted the extracellular electron transfer by constructing a conductive network between catalyst and electrode. However, for suspension-catalysis, the size effect and synergistic effect of bimetallic NPs have a more prominent effect on the degradation of azo dyes. As the increase of Au proportion the particle size decreases, and the catalytic activity of bio-PdxAuy improved significantly. The response principles of bio-PdxAuy proposed in this study provide a reliable reference for the rational design of bio-based bimetallic catalysts with enhanced catalytic performance.