Age structure and body size of two Tibetan toad (Bufo tibetanus) populations from different elevations in China.

Understanding how age and body size vary across elevations can provide insights into the evolution of life-history traits in animals. In the present study, we compared the demographic (using skeletochronology) and morphological traits of the Tibetan toad (Bufo tibetanus) between two populations from different elevational habitats (2650 vs. 3930 m). We found that (1) the mean age and body size of females were significantly greater than those of males in both populations; (2) both sexes of toads from the higher elevation tended to be significantly older in age and larger in body size; (3) there was a significant positive relationship between age and body size within each sex of the toad at both elevations; and (4) growth rates varied between the two populations, with the higher rate observed in the lower-elevation population. Our results suggested that factors other than age, such as elevation-associated temperature, influence the observed differences in body size between the two populations. Future research at a broader range of elevations should focus on these factors and evaluate their influence on animal growth patterns.

Engineering Chimeric Chemoreceptors and Two-Component Systems for Orthogonal and Leakless Biosensing of Extracellular γ-Aminobutyric Acid.

Two-component systems (TCSs) sensing and responding to various stimuli outside and inside cells are valuable resources for developing biosensors with synthetic biology applications. However, the use of TCS-based biosensors suffers from a limited effector spectrum, hypersensitivity, low dynamic range, and unwanted signal crosstalk. Here, we developed a tailor-made Escherichia coli whole-cell γ-aminobutyric acid (GABA) biosensor by engineering a chimeric GABA chemoreceptor PctC and TCS. By testing different TCSs, the chimeric PctC/PhoQ showed the response to GABA. Chimera-directed evolution and introduction of the insulated chimeric pair PctC/PhoQ*PhoP* produced biosensors with up to 3.50-fold dynamic range and good orthogonality. To further enhance the dynamic range and lower the basal leakage, three strategies, engineering of PhoP DNA binding sites, fine-tuning reporter expression by optimizing transcription/translation components, and a tobacco etch virus protease-controlled protein degradation, were integrated. This chimeric biosensor displayed a low basal leakage, a large dynamic range (15.8-fold), and a high threshold level (22.7 g L-1). Finally, the optimized biosensor was successfully applied in the high-throughput microdroplet screening of GABA-overproducing Corynebacterium glutamicum, demonstrating its desired properties for extracellular signal biosensing.

A rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes.

The reactive nitrogen species (RNS) in lysosomes play a major role during the regulation of lysosomal microenvironment. Nitroxyl (HNO) belongs to active nitrogen species (RNS) and is becoming a potential diagnostic and therapeutic biomarker. However, the complex synthesis routes of HNO in biosystem always hinder the exact determination of HNO in living cells. Here, a rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes was constructed and synthesized. 2-(Diphenylphosphino)benzoate was utilized as the sensing unit for HNO and morpholine was chose as the targeting group for lysosome. Before the addition of HNO, the probe displayed a spirolactone structure and almost no fluorescence was found. After the addition of HNO, the probe existed as a conjugated xanthene form and an intense green fluorescence was observed. The fluorescent probe possessed fast response (3 min) and high selectivity for HNO. Furthermore, fluorescence intensity of the probe linearly related with the HNO concentration in the range of 6.0 × 10-8 to 6.0 × 10-5 mol L-1. The detection limit was found to be 1.87 × 10-8 mol L-1 for HNO. Moreover, the probe could selectively targeted lysosome with excellent biocompatibility and had been effectually utilized to recognize exogenous HNO in A549 cells.

Novel Pyrazole-4-Carboxamide Derivatives Containing Oxime Ether Group as Potential SDHIs to Control Rhizoctonia solani.

In the search for novel succinate dehydrogenase inhibitor (SDHI) fungicides to control Rhizoctonia solani, thirty-five novel pyrazole-4-carboxamides bearing either an oxime ether or an oxime ester group were designed and prepared based on the strategy of molecular hybridization, and their antifungal activities against five plant pathogenic fungi were also investigated. The results indicated that the majority of the compounds containing oxime ether demonstrated outstanding in vitro antifungal activity against R. solani, and some compounds also displayed pronounced antifungal activities against Sclerotinia sclerotiorum and Botrytis cinerea. Particularly, compound 5e exhibited the most promising antifungal activity against R. solani with an EC50 value of 0.039 µg/mL, which was about 20-fold better than that of boscalid (EC50 = 0.799 µg/mL) and 4-fold more potent than fluxapyroxad (EC50 = 0.131 µg/mL). Moreover, the results of the detached leaf assay showed that compound 5e could suppress the growth of R. solani in rice leaves with significant protective efficacies (86.8%) at 100 µg/mL, superior to boscalid (68.1%) and fluxapyroxad (80.6%), indicating promising application prospects. In addition, the succinate dehydrogenase (SDH) enzymatic inhibition assay revealed that compound 5e generated remarkable SDH inhibition (IC50 = 2.04 µM), which was obviously more potent than those of boscalid (IC50 = 7.92 µM) and fluxapyroxad (IC50 = 6.15 µM). Furthermore, SEM analysis showed that compound 5e caused a remarkable disruption to the characteristic structure and morphology of R. solani hyphae, resulting in significant damage. The molecular docking analysis demonstrated that compound 5e could fit into the identical binding pocket of SDH through hydrogen bond interactions as well as fluxapyroxad, indicating that they had a similar antifungal mechanism. The density functional theory and electrostatic potential calculations provided useful information regarding electron distribution and electron transfer, which contributed to understanding the structural features and antifungal mechanism of the lead compound. These findings suggested that compound 5e could be a promising candidate for SDHI fungicides to control R. solani, warranting further investigation.

Liquid chromatography with tandem mass spectrometric method for determination of 52 antibiotics in human whole blood and urine and application to forensic cases.

PURPOSE: A rapid and reliable method was developed and validated for the simultaneous analysis of 52 antibiotics (cephalosporins, penicillins, carbapenems, lincosamides, quinolones, nitroimidazoles, macrolides, sulfonamides, tetracyclines, glycopeptide) in urine and whole blood by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). METHOD: Analytes were extracted by dilution or protein precipitation and analyzed on an Agilent 1260 HPLC system coupled to an Agilent 6470 Triple Quadrupole Mass Spectrometer. RESULTS: The method attended method validation criteria. The limits of detection were equal or lower than 2.0 ng/mL, whereas the limits of quantification ranged from 0.1 to 10.0 ng/mL, from 0.1 to 5.0 ng/mL, in urine and whole blood, respectively. For all analytes, the bias and intra- and inter-day precision values were less than 14.7%. The ranges of recovery values of all antibiotics were 76.5-124.5% in whole blood and 76.3-121.8% in urine, values of the effects were lower than 25% in two matrices. No evidence of carryover was observed. The study of sample stability showed that almost all analytes were stable at 24 °C for 24 h, all analytes were stable at -20 °C for 14 days and at -80 °C for 30 days. Freeze-thaw cycles stability showed that antibiotics were stable except for imipenem. Autosampler stability study showed that all analytes were stable for 24 h, except for imipenem and amoxicillin. Applicability was proven by analyzing authentic whole blood (n = 86) and urine (n = 79) samples from patients under antibiotics treatment. Therefore, this method was applied to the analysis 3 forensic allergy cases, which were positive for at least one analyte. CONCLUSIONS: A simple, sensitive and high-throughput method for the simultaneous determination of different classes of antibiotics in urine and whole blood samples was developed and applied. This sensitive method was successfully applied to forensic cases.

Dynamic plasmid copy number control for synthetic biology.

Plasmids that replicate independently from chromosomes are valuable genetic tools for biological research. Dynamic control of plasmid copy number facilitates flexible regulation of the gene of interest or the genetic circuit installed in the plasmid. This useful strategy is being integrated into synthetic biology for metabolic reprogramming and biosensing applications.

A Sensitive Ultra-performance Liquid Chromatography-Tandem Mass Spectrometric Method for Determination of Secalonic Acid F in Rat Plasma and Its Application to Pharmacokinetic Study.

Secalonic acid F (SAF) is a fungal secondary metabolite exhibited interesting pharmacological effect. In this study, a simple and sensitive ultra-performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method was developed and validated for the determination of SAF in rat plasma. Emodin was selected as the internal standard (IS), and plasma samples were prepared by liquid-liquid extraction with ethyl acetate. Chromatographic separation was operated on an Agilent SB-C18 column, and the mobile phase was a mixture of 0.5% formic acid in water and methanol (V:V = 20:80) at a flow rate of 0.3 mL/min. Detection was carried out with a 6460 triple-quadrupole mass spectrometer using electrospray ionization in the multiple-reaction monitoring mode. The MS/MS ion transitions monitored were m/z 639.3 â†’ 415.4 and 269.0 â†’ 225.1 for SAF and IS, respectively. Results showed the calibration curve of SAF was linear in the range of 2-500 ng·mL-1 with the correlation coefficient > 0.99. The matrix effect, extraction recovery, dilution effect, intraday and inter-day precision and accuracy were all in acceptable limits. The analytes were also stable under different conditions. The validated method was successfully applied to a pharmacokinetic study after oral administration in Sprague-Dawley rats at a dose of 10 mg/kg.

An Organic Coordination Manganese Complex as Cathode for High-Voltage Aqueous Zinc-metal Battery.

Aqueous Zn-Mn battery has been considered as the most promising scalable energy-storage system due to its intrinsic safety and especially ultralow cost. However, the traditional Zn-Mn battery mainly using manganese oxides as cathode shows low voltage and suffers from dissolution/disproportionation of the cathode during cycling. Herein, for the first time, a high-voltage and long-cycle Zn-Mn battery based on a highly reversible organic coordination manganese complex cathode (Manganese polyacrylate, PAL-Mn) was constructed. Benefiting from the insoluble carboxylate ligand of PAL-Mn that can suppress shuttle effect and disproportionationation reaction of Mn3+ in a mild electrolyte, Mn3+ /Mn2+ reaction in coordination state is realized, which not only offers a high discharge voltage of 1.67 V but also exhibits excellent cyclability (100 % capacity retention, after 4000 cycles). High voltage reaction endows the Zn-Mn battery high specific energy (600 Wh kg-1 at 0.2 A g-1 ), indicating a bright application prospect. The strategy of introducing carboxylate ligands in Zn-Mn battery to harness high-voltage reaction of Mn3+ /Mn2+ well broadens the research of high-voltage Zn-Mn batteries under mild electrolyte conditions.

Ag Nanoparticle and Ti-MOF Cooperativity for Efficient Inactivation of E. coli in Water.

Because of the limitations of traditional chlorine-based bactericidal water treatment, such as the formation of disinfection byproducts (DBPs) and resistance to chlorine, novel approaches and materials are required for effective disinfection of water. This study focuses on the development of a new sterilization material, Ag/NH2-MIL-125(Ti), which was designed to effectively inactivate Escherichia coli in water. The effectiveness of the as-designed material stems from the synergistic interactions between Ag nanoparticles (NPs) and photoactive metal-organic frameworks (MOFs). In this complex material, the MOFs play a critical role in dispersing and isolating the Ag NPs, thus preventing undesirable aggregation during bacterial inactivation. Simultaneously, Ag NPs enhance the photocatalytic performance of the MOFs. Sterilization experiments demonstrate the remarkable rapid E. coli inactivation performance of Ag/NH2-MIL-125(Ti) under illuminated and nonilluminated conditions. Within 25 min of visible light exposure, the as-prepared material achieves a >7-log E. coli reduction. In addition, Ag/NH2-MIL-125(Ti) efficiently decomposes acetic acid, which is the main DBP precursor, under visible light irradiation. Mechanistic investigations revealed that •O2- and h+ were the primary active substances responsible for the inactivation of E. coli and the decomposition of acetic acid, respectively.

Burden of oral disorders, 1990-2019: estimates from the Global Burden of Disease Study 2019.

Introduction: The aim of this study was to understand the global incidence and disability-adjusted life years (DALY) of oral disorders by age, gender, region, and Sociodemographic Index (SDI) from 1990 to 2019. Material and methods: The estimated annual percentage change (EAPC) and 95% confidence intervals (CIs) were used to assess the trends in age-standardized incidence and DALY rates from 1990 to 2019. Results: The global age-standardized incidence rate (EAPC = 0.01) of oral disorders increased slightly from 1990 to 2019. From 1990 to 2019, the age-standardized DALY rate decreased in high-SDI (EAPC = -0.43) and high-middle-SDI (EAPC = -0.14) regions, but it showed increasing trends in low-SDI (EAPC = 0.22), low-middle-SDI (EAPC = 0.36), and middle-SDI (EAPC = 0.17) regions. The EAPC in the age-standardized DALY rate was negatively correlated with the regional SDI value (ρ = -0.402, p = 0.001). From 1990 to 2019, the region with the largest increase in age-standardized DALY rate was South Asia (EAPC = 0.67), while the country with the greatest increase in age-standardized DALY rate was India (EAPC = 0.82). Conclusions: From 1990 to 2019, the global age-standardized incidence rate of oral disorders showed a slight increasing trend. It is necessary to control the increase in DALY and the disease burden associated with oral disorders in low-, low-middle-, and middle-SDI regions, such as South Asia, particularly in India.

An overview on CV2/CRMP5 antibody-associated paraneoplastic neurological syndromes.

Paraneoplastic neurological syndrome refers to certain malignant tumors that have affected the distant nervous system and caused corresponding dysfunction in the absence of tumor metastasis. Patients with this syndrome produce multiple antibodies, each targeting a different antigen and causing different symptoms and signs. The CV2/collapsin response mediator protein 5 (CRMP5) antibody is a major antibody of this type. It damages the nervous system, which often manifests as limbic encephalitis, chorea, ocular manifestation, cerebellar ataxia, myelopathy, and peripheral neuropathy. Detecting CV2/CRMP5 antibody is crucial for the clinical diagnosis of paraneoplastic neurological syndrome, and anti-tumor and immunological therapies can help to alleviate symptoms and improve prognosis. However, because of the low incidence of this disease, few reports and no reviews have been published about it so far. This article intends to review the research on CV2/CRMP5 antibody-associated paraneoplastic neurological syndrome and summarize its clinical features to help clinicians comprehensively understand the disease. Additionally, this review discusses the current challenges that this disease poses, and the application prospects of new detection and diagnostic techniques in the field of paraneoplastic neurological syndrome, including CV2/CRMP5-associated paraneoplastic neurological syndrome, in recent years.

An ICT-FRET-based ratiometric fluorescent probe for hydrogen polysulfide based on a coumarin-naphthalimide derivative.

Hydrogen polysulfide (H2Sn, n > 1), as one of the important members of reactive sulfur species (RSS), plays a vital part in the processes of both their physiology and pathology. In this work, a ratiometric fluorescent probe for H2Sn had been designed and prepared based on the combination mechanism of intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET). The probe chose a coumarin derivative as the energy donor, a naphthalimide derivative as the energy acceptor and 2-fluoro-5-nitrobenzoate as the H2Sn recognition group. When H2Sn was not present in the system, the ICT process of the naphthalimide acceptor was inhibited and the FRET process from the coumarin donor to the naphthalimide acceptor was turned off. When H2Sn was added, both ICT and FRET occurred due to the nucleophilic substitution-cyclization reactions between the probe and hydrogen polysulfide. In addition, the ratio value of the emission intensities at 550 nm and 473 nm (I550 nm/I473 nm) of this probe had a good linear relationship with H2Sn concentration in the range of 6.0 × 10-7-5.0 × 10-5 mol·L-1, and a detection limit of 1.8 × 10-7 mol·L-1 was obtained. The developed probe had high selectivity and sensitivity, as well as good biocompatibility. Additionally, the probe had been used to successfully image both indigenous and exogenous hydrogen polysulfide in A549 cells using confocal microscope.

Association between bilirubin levels and risk of stroke: a systematic review and meta-analysis.

OBJECTIVE: To evaluate the association between bilirubin levels and stroke risk. DESIGN: Systematic review and meta-analysis, reported in accordance with Meta-analysis Of Observational Studies in Epidemiology guidelines. DATA SOURCES: The PubMed, Embase, Cochrane Central Register of Controlled Trials and China National Knowledge Infrastructure Databases were searched from inception up to 27 February 2022. ELIGIBILITY CRITERIA: Cohort studies assessing the dose-response relationship between bilirubin levels and risk of stroke were eligible for inclusion. There were no language restrictions. DATA EXTRACTION AND SYNTHESIS: All data from eligible studies were collected and assessed by two independent investigators. We generated pooled relative risks (RRs) with 95% CIs. We used a restricted cubic spline model for the dose-response analyses. Subsequent subgroup analyses were conducted according to stroke outcomes, follow-up duration, geographical area and size of the cohort. RESULTS: Nine articles including results from 11 cohort studies with 7835 cases of stroke and 263 596 participants met the inclusion criteria. The summarised RR of stroke comparing the highest and lowest bilirubin level was 0.85 (95% CI 0.72 to 0.99). The dose-response analysis indicated that a 15 µmol/L increment of bilirubin level was associated with an 18% lower risk of stroke (RR=0.82, 95% CI 0.67 to 0.99). For ischaemic stroke, the RR was 0.76 (95% CI 0.58 to 0.99). Significant publication bias was not detected. CONCLUSIONS: Elevated bilirubin levels were associated with a decreased risk of stroke among adults. PROSPERO REGISTRATION NUMBER: CRD42017071497.

Gut microbiota of two invasive fishes respond differently to temperature.

Temperature variation structures the composition and diversity of gut microbiomes in ectothermic animals, key regulators of host physiology, with potential benefit to host or lead to converse results (i.e., negative). So, the significance of either effect may largely depend on the length of time exposed to extreme temperatures and how rapidly the gut microbiota can be altered by change in temperature. However, the temporal effects of temperature on gut microbiota have rarely been clarified. To understand this issue, we exposed two juvenile fishes (Cyprinus carpio and Micropterus salmoides), which both ranked among the 100 worst invasive alien species in the world, to increased environmental temperature and sampled of the gut microbiota at multiple time points after exposure so as to determine when differences in these communities become detectable. Further, how temperature affects the composition and function of microbiota was examined by comparing predicted metagenomic profiles of gut microbiota between treatment groups at the final time point of the experiment. The gut microbiota of C. carpio was more plastic than those of M. salmoides. Specifically, communities of C. carpio were greatly altered by increased temperature within 1 week, while communities of M. salmoides exhibit no significant changes. Further, we identified 10 predicted bacterial functional pathways in C. carpio that were temperature-dependent, while none functional pathways in M. salmoides was found to be temperature-dependent. Thus, the gut microbiota of C. carpio was more sensitive to temperature changes and their functional pathways were significantly changed after temperature treatment. These results showed the gut microbiota of the two invasive fishes differ in response to temperature change, which may indicate that they differ in colonization modes. Broadly, we have confirmed that the increased short-term fluctuations in temperatures are always expected to alter the gut microbiota of ectothermic vertebrates when facing global climate change.

FcRn inhibitors: a novel option for the treatment of myasthenia gravis.

Myasthenia gravis is an acquired, humoral immunity-mediated autoimmune disease characterized by the production of autoantibodies that impair synaptic transmission at the neuromuscular junction. The intervention-mediated clearance of immunoglobulin G (IgG) was shown to be effective in controlling the progression of the disease. The neonatal Fc receptor (FcRn) plays a key role in prolonging the serum half-life of IgG. Antagonizing FcRn to prevent its binding to IgG can accelerate the catabolism of the latter, resulting in decreased levels of IgG, including pathogenic autoantibodies, thereby achieving a therapeutic effect. In this review, we detail the substantial research progress, both basic and clinical, relating to the use of FcRn inhibitors in the treatment of myasthenia gravis.

A naphthalimide-based and Golgi-targetable fluorescence probe for quantifying hypochlorous acid.

The Golgi apparatus (GA) is a vital organelle in biological systems and excess reactive oxygen species (ROS) is produced during stress in the Golgi apparatus. Hypochlorous acid (HOCl) is a significant reactive oxygen species and has strong oxidative and antibacterial activity, but excessive secretion of hypochlorous acid can affect Golgi structure or function abnormally, it will lead to a series of diseases including Alzheimer's disease, neurodegenerative diseases, autoimmune diseases, and Parkinson's disease. In present work, a novel fluorescent probe for Golgi localization utilizing naphthalimide derivatives was constructed to detect hypochlorous acid. The fluorescent probe used a derivatived 1,8-naphthalimide as the emitting fluorescence group, phenylsulfonamide as the localization group and dimethylthiocarbamate as the sensing unit. When HOCl was absent, the intramolecular charge transfer (ICT) process of the developed probe was hindered and the probe exhibited a weak fluorescence. When HOCl was present, the ICT process occurred and the probe showed strong green fluorescence. When the HOCl concentration was altered from 5.0 × 10-7 to 1.0 × 10-5 mol·L-1, the fluorescence intensity of the probe well linearly correlated with the HOCl concentration. The detection limit of 5.7 × 10-8 mol·L-1 was obtained for HOCl. The HOCl fluorescent probe possessed a rapid reaction time, a high selectivity and a broad working pH scope. In addition, the probe possessed good biocompatibility and had been magnificently employed to image Golgi HOCl in Hela cells. These characteristics of the probe demonstrated its ability to be used for sensing endogenous and exogenous hypochlorous acids within the Golgi apparatus of living cells.

Association between loneliness and dementia risk: A systematic review and meta-analysis of cohort studies.

Loneliness has been reported to be associated with an increased risk of dementia; however, the extent of this relationship remains controversial. This study aimed to assess the strength of the relationship between loneliness and dementia using a meta-analysis approach. PubMed, EMBASE, and China National Knowledge Internet databases were systematically searched for potentially included studies from inception up to 17 February 2022. A meta-analysis was performed using a random-effects model to assess pooled relative risks (RRs) and 95% confidence intervals (CIs). A literature search identified 16 cohort studies (published in 15 articles), among which 4,625 dementia cases and 62,345 individuals were selected for further meta-analysis. Loneliness was associated with an increased risk of Alzheimer's disease (AD) (RR: 1.72, 95% CI: 1.32-2.23; P < 0.001) and dementia (RR: 1.23, 95% CI: 1.16-1.31; P < 0.00001). However, no significant association between loneliness and risk of mild cognitive impairment (MCI) (RR: 1.34, 95% CI: 0.97-1.87; P = 0.080) or vascular dementia (VaD) (RR: 1.01, 95% CI: 0.51-1.99; P = 0.973) was observed. Results revealed that loneliness might increase the risk of Alzheimer's disease and dementia. Early interventions that limit loneliness may reduce risk of dementia and Alzheimer's disease.

Copper-induced oxidative stress, transcriptome changes, intestinal microbiota, and histopathology of common carp (Cyprinus carpio).

Copper (Cu) is a common contaminant in aquatic environments, which could cause physiological dysfunction in aquatic organisms. However, few studies have comprehensively examined the impact of copper toxicity in freshwater fish over the past decade. In this research, the oxidative stress, liver transcriptome, intestinal microbiota, and histopathology of common carp (C. carpio) in response to Cu exposure were studied, by exposing juvenile carp to 0.2 mg/ml Cu2+ for 30 days. The results revealed that Cu2+ could induce significant changes in malondialdehyde (MDA) content and antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)) activity. The changes in antioxidant enzyme activities indicate that Cu can induce oxidative stress by generating reactive oxygen species (ROS) content. RNA-seq analysis of the liver identified 1069 differentially expressed genes (DEGs) after treatment with 2.0 mg/L Cu2+. Among the DEGs, 490 genes were upregulated and 579 genes were downregulated. GO functional enrichment analysis revealed that Cu could affect the fatty acid biosynthetic process, carnitine biosynthetic process, and activity of carboxylic acid transmembrane transporter. Meanwhile, the most significantly enriched KEGG pathway also included the lipid metabolism pathway. In addition, Cu2+ exposure increased bacterial richness and changed bacterial composition. At the phylum level, we found that the ratio of Bacteroidetes to Firmicutes was increased in the treatment carps, which can regulate intestinal epithelium function and reduce inflammation and immune responses. At the genus level, the abundances of 11 genera were significantly altered after exposure to Cu2+. The altered composition of the microbial community caused by Cu exposure may play a useful role in compensation of the intestinal lesions by Cu exposure. Furthermore, we found that Cu2+ exposure could cause histological alterations such as structural damage to the liver and intestines. The results of this research contribute to a better understanding of mechanisms related to Cu toxicity in fish.

Soil metagenomic analysis on changes of functional genes and microorganisms involved in nitrogen-cycle processes of acidified tea soils.

Nitrogen (N) is the first essential nutrient for tea growth. However, the effect of soil acidification on soil N cycle and N forms in tea plantation are unclear. In this study, the nitrogen contents, soil enzyme activity and N mineralization rate in acidified soil of tea plantation were measured. Moreover, the effects of soil acidification on N cycling functional genes and functional microorganisms were explored by soil metagenomics. The results showed that the NH4 +-N, available N and net N mineralization rate in the acidified tea soil decreased significantly, while the NO3 --N content increased significantly. The activities of sucrase, protease, catalase and polyphenol oxidase in the acidified tea soil decreased significantly. The abundance of genes related to ammonification, dissimilatory N reduction, nitrification and denitrification pathway in the acidified tea soil increased significantly, but the abundance of functional genes related to glutamate synthesis and assimilatory N reduction pathway were opposite. In addition, the abundance of Proteobacteria, Actinobacteria, Chloroflexi, Nitrospirae, Actinomadura, Nitrospira etc. microorganisms related to nitrification, denitrification and pathogenic effect increased significantly in the acidified tea soil. The correlation results showed that soil pH and N forms were correlated with soil enzyme activity, N cycling function genes and microbial changes. In conclusion, soil acidification results in significant changes in enzyme activity, gene abundance and microorganism involved in various N cycle processes in acidified tea soil, which leads to imbalance of soil N form ratio and is not conducive to N transformation and absorption of tea trees.

Rhodamine-Based Fluorescent Probe for Highly Selective Determination of Hg2.

The determination of mercuric ions (Hg2+) in environmental and biological samples has attracted the attention of researchers lately. In the present work, a novel turn-on Hg2+ fluorescent probe utilizing a rhodamine derivative had been constructed and prepared. The probe could highly sensitively and selectively sense Hg2+. In the presence of excessive Hg2+, the probe displayed about 52-fold fluorescence enhancement in 50% H2O/CH3CH2OH (pH, 7.24). In the meantime, the colorless solution of the probe turned pink upon adding Hg2+. Upon adding mercuric ions, the probe interacted with Hg2+ and formed a 1:1 coordination complex, which had been the basis for recognizing Hg2+. The probe displayed reversible dual colorimetric and fluorescence sensing of Hg2+ because rhodamine's spirolactam ring opened upon adding Hg2+. The analytical performances of the probe for sensing Hg2+ were also studied. When the Hg2+ concentration was altered in the range of 8.0 × 10-8 to 1.0 × 10-5 mol L-1, the fluorescence intensity showed an excellent linear correlation with Hg2+ concentration. A detection limit of 3.0 × 10-8 mol L-1 had been achieved. Moreover, Hg2+ in the water environment and A549 cells could be successfully sensed by the proposed probe.