Efficient, specific and direct detection of double-stranded DNA targets using Cas12f1 nucleases and engineered guide RNAs.

To address the limitations of the CRISPR/Cas12f1 system in clinical diagnostics, which require the complex preparation of single-stranded DNA (ssDNA) or in vitro transcripts (RNA), we developed a fluorescent biosensor named PDTCTR (PAM-dependent dsDNA Target-activated Cas12f1 Trans Reporter). This innovative biosensor integrates Recombinase Polymerase Amplification (RPA) with the Cas12f_ge4.1 system, facilitating the direct detection of double-stranded DNA (dsDNA). PDTCTR represents a significant leap forward, exhibiting a detection sensitivity that is a hundredfold greater than the original Cas12f1 system. It demonstrates the capability to detect Mycoplasma pneumoniae (M. pneumoniae) and Hepatitis B virus (HBV) with excellent sensitivity of 10 copies per microliter (16.8 aM) and distinguishes single nucleotide variations (SNVs) with high precision, including the EGFR (L858R) mutations prevalent in non-small cell lung cancer (NSCLC). Clinical evaluations of PDTCTR have demonstrated its high sensitivity and specificity, with rates ranging from 93%-100% and 100%, respectively, highlighting its potential to revolutionize diagnostic approaches for infectious diseases and cancer-related SNVs.This research underscores the substantial advancements in CRISPR technology for clinical diagnostics and its promising future in early disease detection and personalized medicine.

The microbial carbon pump and climate change.

The ocean has been a regulator of climate change throughout the history of Earth. One key mechanism is the mediation of the carbon reservoir by refractory dissolved organic carbon (RDOC), which can either be stored in the water column for centuries or released back into the atmosphere as CO2 depending on the conditions. The RDOC is produced through a myriad of microbial metabolic and ecological processes known as the microbial carbon pump (MCP). Here, we review recent research advances in processes related to the MCP, including the distribution patterns and molecular composition of RDOC, links between the complexity of RDOC compounds and microbial diversity, MCP-driven carbon cycles across time and space, and responses of the MCP to a changing climate. We identify knowledge gaps and future research directions in the role of the MCP, particularly as a key component in integrated approaches combining the mechanisms of the biological and abiotic carbon pumps for ocean negative carbon emissions.

Self-Assembled Layer of Organic Phosphonic Acid Enables Highly Stable MnO2 Cathode for Aqueous Znic Batteries.

Manganese dioxide (MnO2) is an attractive cathode material for aqueous zinc batteries (AZBs) owing to its environmental benignity, low cost, high operating voltage, and high theoretical capacity. However, the severe dissolution of Mn2+ leads to rapid capacity decay. Herein, a self-assembled layer of amino-propyl phosphonic acid (AEPA) on the MnO2 surface, which significantly improves its cycle performance is successfully modified. Specifically, AEPA can be firmly attached to MnO2 through a strong chemical bond, forming a hydrophobic, and uniform organic coating layer with a few nanometers thickness. This coating layer can significantly inhibit the dissolution of Mn2+ by avoiding the direct contact between the electrolyte and cathode, thus enhancing the structural integrity and redox reversibility of MnO2. As a result, the MnO2@AEPA cathode achieves a high reversible capacity of 223 mAh g-1 at 0.5 A g-1 and a high capacity retention of 97% after 1700 cycles at 1 A g-1. This work provides new insights in developing stable Mn-based cathodes for aqueous batteries.

Survival of surface bacteriophages and their hosts in in situ deep-sea environments.

IMPORTANCE: The survival of the sinking prokaryotes and viruses in the deep-sea environment is crucial for deep-sea ecosystems and biogeochemical cycles. Through an in situ deep-sea long-term incubation device, our results showed that viral particles and infectivity had still not decayed completely after in situ incubation for 1 year. This suggests that, via infection and lysis, surface viruses with long-term infectious activity in situ deep-sea environments may influence deep-sea microbial populations in terms of activity, function, diversity, and community structure and ultimately affect deep-sea biogeochemical cycles, highlighting the need for additional research in this area.

A Cascade Signal Amplification Strategy for the Ultrasensitive Fluorescence Detection of Cu2+ via λ-Exonuclease-Assisted Target Recycling with Mismatched Catalytic Hairpin Assembly.

Herein, an ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu2+ was designed using the cascade signal amplification strategy, coupling λ-exonuclease-assisted target recycling and mismatched catalytic hairpin assembly (MCHA). In the designed detection system, the target, Cu2+, can activate the Cu2+-dependent DNAzyme to cause a cleavage reaction, releasing ssDNA (tDNA). Then, tDNA binds to hairpin DNA (H0) with an overhanging 5'-phosphorylated terminus to form dsDNA with a blunt 5'-phosphorylated terminus, which activates the dsDNA to be digested by λ-Exo and releases tDNA along with another ssDNA (iDNA). Subsequently, the iDNA initiates MCHA, which can restore the fluorescence of carboxyfluorescein (FAM) previously quenched by tetramethylrhodamine (TAMRA), resulting in a strong fluorescent signal. Furthermore, MCHA efficiently improves the signal-to-noise ratio of the detection system. More importantly, tDNA recycling can be achieved with the λ-Exo digestion reaction to release more iDNA, efficiently amplifying the fluorescent signal and further improving the sensitivity to Cu2+ with a detection limit of 60 fM. The practical application of the developed biosensor was also demonstrated by detecting Cu2+ in real samples, proving it to be an excellent analytical strategy for the ultrasensitive quantification of heavy metal ions in environmental water sources.

Research progress in the detection of common foodborne hazardous substances based on functional nucleic acids biosensors.

With the further improvement of food safety requirements, the development of fast, highly sensitive, and portable methods for the determination of foodborne hazardous substances has become a new trend in the food industry. In recent years, biosensors and platforms based on functional nucleic acids, along with a range of signal amplification devices and methods, have been established to enable rapid and sensitive determination of specific substances in samples, opening up a new avenue of analysis and detection. In this paper, functional nucleic acid types including aptamers, deoxyribozymes, and G-quadruplexes which are commonly used in the detection of food source pollutants are introduced. Signal amplification elements include quantum dots, noble metal nanoparticles, magnetic nanoparticles, DNA walkers, and DNA logic gates. Signal amplification technologies including nucleic acid isothermal amplification, hybridization chain reaction, catalytic hairpin assembly, biological barcodes, and microfluidic system are combined with functional nucleic acids sensors and applied to the detection of many foodborne hazardous substances, such as foodborne pathogens, mycotoxins, residual antibiotics, residual pesticides, industrial pollutants, heavy metals, and allergens. Finally, the potential opportunities and broad prospects of functional nucleic acids biosensors in the field of food analysis are discussed.

Recent advances in nanostructured substrates for surface-enhanced infrared absorption spectroscopy.

Surface-enhanced infrared absorption (SEIRA) spectroscopy is an emerging research field that has received much attention from the research community. Unlike conventional infrared absorption spectroscopy, SEIRA spectroscopy is a surface sensitive technique that exploits the electromagnetic properties of nanostructured substrates to amplify the vibrational signals of adsorbed molecules. Unique advantages like high sensitivity, wide adaptability, and convenient operation allow SEIRA spectroscopy to be applied in qualitative and quantitative analyses for traces of gases, biomolecules, polymers, and so on. In this review, we summarize recent advances in nanostructured substrates for SEIRA spectroscopy, including the developing history and widely accepted SEIRA mechanisms of SEIRA spectroscopy. Most importantly, characteristics and preparation methods of representative SEIRA-active substrates are introduced. In addition, current deficiencies and prospects in the field of SEIRA spectroscopy are discussed.

Two Fe(III)/Eu(III) Salophen complex-based optical sensors for determination of organophosphorus pesticide monocrotophos.

Monocrotophos (MP), an organophosphorus pesticide, poses a serious threat to human health, so a rapid and simple technique is needed to detect it. In this study, two novel optical sensors for MP detection were created using the Fe(III) Salophen complex and Eu(III) Salophen complex, respectively. One sensor is an Fe(III) Salophen complex (I-N-Sal), which can bind MP selectively and form a supramolecule, resulting in a strong resonance light scattering (RLS) signal at 300 nm. Under the optimum conditions, the detection limit was 30 nM, the linear range was 0.1-1.1 µM, the correlation coefficient R2 = 0.9919, and the recovery rate range was 97.0-103.1%. Interaction properties between the sensor I-N-Sal and MP and the RLS mechanism were investigated using density functional theory (DFT). And another sensor is based on the Eu(III) Salophen complex and 5-aminofluorescein derivatives. The Eu(III) Salophen complex was immobilized on the surface of amino-silica gel (Sigel-NH2) particles as the solid phase receptor (ESS) of MP and 5-aminofluorescein derivatives as the fluorescent (FL)-labeled receptor (N-5-AF) of MP, which can selectively bind the MP and form a sandwich-type supramolecule. Under the optimum conditions, the detection limit was 0.4 µM, the linear range was 1.3-7.0 µM, the correlation coefficient R2 = 0.9983, and the recovery rate range was 96.6-101.1%. Interaction properties between the sensor and MP were investigated by UV-vis, FT-IR, and XRD. Both sensors were successfully applied to the determination of MP content in tap water and camellia.

Sequestration of strontium, nickel, and cadmium on glomalin-related soil protein: Interfacial behaviors and ecological functions.

Glomalin-related soil protein (GRSP) is a widespread recalcitrant soil protein complex that promotes the immobilization of metals in soils. Herein, we combined indoor simulation and field investigation to reveal the interfacial behaviors and ecological functions of GRSP to the three typical metals (Sr(II), Ni(II), and Cd(II)). The kinetic and isotherm data suggested that GRSP had a strong ability to adsorb the metals, which was closely related to the Hard-Soft-Acid-Base theory and the film diffusion mechanisms. Regarding environmental factors, the higher solution pH was beneficial to the adsorption of the metals onto GRSP, while the adsorption capacity decreased at lower or higher salinity due to the salting-out and Na+ competition effects. Moreover, Sr(II), Ni(II), and Cd(II) showed competitive adsorption onto GRSP, which was associated with the spatial site resistance effect. By comparing the retention factors of seven natural and artificial particles, GRSP had elevated distribution coefficients in high metal concentration, while its retention factors showed a relatively lower decrease, suggesting that GRSP had excellent buffer performance for a potential metal pollution emergency. Through the continental-scale coastal regions investigation, GRSP sequestered 1.05-3.11 µmol/g Ni, 0.31-1.49 µmol/g Sr, and 0.01-0.06 µmol/g Cd with 0.54-0.91 % of the sediment mass, demonstrating its strong ability to adsorb the metals. Therefore, we advocate that GRSP, as a recalcitrant protein complex, can be considered an effective tool for buffering capacity of metal pollution and environmental capacity within coastal wetlands.

Green synthesis of CQDs for determination of iron and isoniazid in pharmaceutical formulations.

Camphor leaves were used as the precursor for the hydrothermal synthesis of carbon quantum dots. The preparation method is simple and rapid, and the raw material is environmentally friendly and easy to obtain. Without additional modification, the carbon quantum dots were used as fluorescent probes for the sensitive and selective detection of Fe3+ and isoniazid at different excitation wavelengths. For Fe3+, at the excitation wavelength of 320 nm, the ratio of fluorescence intensity of CQD solution after adding Fe3+ to CQD solution without Fe3+ addition, F/F0, and Fe3+ concentration showed a good linear relationship in the range of 2.72 × 10-5 to 1.00 × 10-4 mol L-1 (R2 = 0.9912), and the limit of detection was 8.16 µmol L-1. For isoniazid, at the excitation wavelength of 270 nm, the ratio of fluorescence intensity of CQDs solution with isoniazid to CQDs solution without isoniazid, F/F0, and isoniazid concentration showed good linear relationships in the range of 3.81 × 10-6 to 1.00 × 10-5 mol L-1 (R2 = 0.9941) and 1.00 × 10-5 to 2.10 × 10-4 mol L-1 (R2 = 0.9910) respectively, and the limit of detection was 1.14 µmol L-1. A fluorescence method for the determination of Fe and isoniazid content was proposed. The method has been used to detect iron in iron supplement tablets and isoniazid in isoniazid tablets with satisfactory results.

Strategy of In Situ Electrochemical Regulation for Highly Enhanced Nonenzymatic Sensing of Carbaryl.

Specific and sensitive sensing of most pesticide residues relies on enzymes such as acetylcholinesterase and advanced materials, which need to be loaded on the surface of working electrodes, leading to instability, uneven surface, tedious process, and high cost. Meanwhile, employing certain potential or current in electrolyte solution could also modify the surface in situ and overcome these drawbacks. However, this method is only regarded as electrochemical activation widely applied in the pretreatment of electrodes. In this paper, by means of regulating the electrochemical technique and its parameters, we prepared a proper sensing interface and derivatized the carbaryl (a carbamate pesticide) hydrolyzed form (1-naphthol) to enhance sensing by 100 times within several minutes. After regulation I by chronopotentiometry with 0.2 mA for 20 s or chronoamperometry with 2 V for 10 s, abundant oxygen-containing groups form and the ordered carbon structure is destroyed. Sweeping from -0.5 to 0.9 V through cyclic voltammetry for only one segment, following regulation II, the composition of oxygen-containing groups changes and the disordered structure is alleviated. Finally, on the constructed sensing interface, test by regulation III through differential pulse voltammetry from 0.8 to -0.4 V, resulting in derivatization of 1-naphthol during 0.8-0 V, followed by electroreduction of the derivative at around -0.17 V. Compared with the electro-oxidation peak at 0.5 V in previous reports, it is essential to improve specificity, even toward several other carbamate pesticides with similar structures. Hence, the in situ electrochemical regulation strategy has demonstrated great potential for effective sensing of electroactive molecules.

Variation of glomalin-metal binding capacity in 1 m soil profiles from mangrove forests to mudflat and affected factor analysis.

Glomalin-related soil protein (GRSP) plays an important role in soil metal sequestration in coastal wetlands. Additionally, it can release dissolved organic matter (GDOM) in water-soaked condition. The purpose of this study was to clarify the variation of GRSP's heavy metal immobilisation capacity at soil profiles of coastal wetland, and explore the compositional characteristics of GDOM and its influence on the heavy metals' environmental behaviour. The results indicated that the metal immobilisation capacity of GRSP decreased with increasing burial depth. The contributions of GRSP to soil Cr, As, and Pb were higher in both mangrove soils (K. obovata and A. marina forests) than in the mudflat. Oxygen-containing functional groups of GRSP (CO, -COO-, etc.) played a positive role in heavy metals accumulation. Redundancy analysis (RDA) showed that high soil pH was not conducive to the enrichment of heavy metals by GRSP. Besides, the concentrations of GRSP-Fe showed a significant positive correlation with the concentrations of other metals (Cu, As, and Pb) in GRSP. It is speculated that the Fe minerals in GRSP contributed the enrichment of heavy metals. Based on PARAFAC modelling, four fluorescent components of GDOM were identified, including three humic-like fluorescent components and one tyrosine-like fluorescent component. The contributions of GDOM to GRSP-bound heavy metals fluctuated between 4.05 % and 88.80 %, which could enhance the fluidity of heavy metals in water and weaken the soil heavy metal immobilisation capacity of GRSP. High salinity exerted an inhibitory effect on the heavy metal content of the GDOM. This study comprehensively explored the potential of GRSP to immobilise heavy metals in wetland soils and highlighted the potential heavy metal risks associated with the GDOM component in water, which could contribute to the multidimensional assessment and control of heavy metal pollution in coastal wetlands.

Oxygen availability driven trends in DOM molecular composition and reactivity in a seasonally stratified fjord.

Ocean deoxygenation could potentially trigger substantial changes in the composition and reactivity of dissolved organic matter (DOM) pool, which plays an important role in the global carbon cycle. To evaluate links between DOM dynamics and oxygen availability, we investigated the DOM composition under varying levels of oxygen in a seasonally hypoxic fjord through a monthly time-series over two years. We used ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to characterize DOM on a molecular level. We find a clear trend both in diversity and molecular composition of the DOM along the oxygen gradient. As oxygen decreased, the chemodiversity was significantly increased, along with accumulation of relatively high-molecular-weight, reduced and unsaturated compounds enriched with carboxyl-group structures, which were also thermodynamically less favorable to biodegradation. Our results suggested that oxygen depletion selectively protected otherwise bioavailable compounds from decomposition and may promote the accumulation of a larger recalcitrant DOM pool in the global ocean, which could provide negative feedback to the ocean carbon sequestration and climate change.

A Novel Electrochemical Sensor Modified with a Computer-Simulative Magnetic Ion-Imprinted Membrane for Identification of Uranyl Ion.

In this paper, a novel ion-imprinted electrochemical sensor modified with magnetic nanomaterial Fe3O4@SiO2 was established for the high sensitivity and selectivity determination of UO22+ in the environment. Density functional theory (DFT) was employed to investigate the interaction between templates and binding ligands to screen out suitable functional binding ligand for the reasonable design of the ion imprinted sensors. The MIIP/MCPE (magnetic ion imprinted membrane/magnetic carbon paste electrode) modified with Fe3O4@SiO2 exhibited a strong response current and high sensitivity toward uranyl ion comparison with the bare carbon paste electrodes. Meanwhile, the MCPE was fabricated simultaneously under the action of strong magnetic adsorption, and the ion imprinted membrane can be adsorbed stably on the electrode surface, handling the problem that the imprinted membrane was easy to fall off during the process of experimental determination and elution. Based on the uranyl ion imprinting network, differential pulse voltammetry (DPV) was adopted for the detection technology to realize the electrochemical reduction of uranyl ions, which improved the selectivity of the sensor. Thereafter, uranyl ions were detected in the linear concentration range of 1.0 × 10-9 mol L-1 to 2.0 × 10-7 mol L-1, with the detection and quantification limit of 1.08 × 10-9 and 3.23 × 10-10 mol L-1, respectively. In addition, the sensor was successfully demonstrated for the determination of uranyl ions in uranium tailings soil samples and water samples with a recovery of 95% to 104%.

Ultrasensitive, Specific, and Rapid Detection of Mycoplasma pneumoniae Using the ERA/CRISPR-Cas12a Dual System.

Mycoplasma pneumoniae can cause severe respiratory tract infections and extrapulmonary diseases, which pose a significant threat to the health of children. Diagnostic methods for M. pneumoniae include isolation and culture, antibody detection, fluorescence quantitative PCR, and so on, but there are various shortcomings in time, cost, convenience, and sensitivity. In this study, we developed a rapid, sensitive, specific, and economical method for the detection of M. pneumoniae, termed the ERA/CRISPR-Cas12a dual system. The system used the high specificity and collateral cleavage activity of the LbCas12a protein, combined with enzymatic recombination amplification (ERA) technology with strong amplification ability, allowing the results to be observed by a portable fluorometer or visualized by the naked eye with a dipstick, which could be obtained in approximately 30 min. The ERA/CRISPR-Cas12a fluorescence and dipstick system were able to detect M. pneumoniae at titers as low as 1 and 100 copies/µL, respectively. The specificity of the two interpretation methods was 100%, and no cross-reaction with other pathogens was observed. In the evaluation of 92 clinical samples, the positive predictive agreements of the ERA/CRISPR-Cas12a fluorescence and dipstick systems with qPCR detection were 100% and 92.86%, respectively. The negative predictive agreements of both methods were 100%. In conclusion, this study established a portable, rapid, low-cost, ultrasensitive, and specific method for the early and rapid diagnosis of M. pneumoniae to meet the needs of on-site rapid detection in primary health institutions.

Highly sensitive and efficient fluorescent sensing for Hg2+ detection based on triple-helix molecular switch and exonuclease III-assisted amplification.

Here, a novel fluorescent sensing for simple, highly sensitive and efficient detection of Hg2+ was developed as joint result of triple-helix molecular switch (THMS) and exonuclease III (Exo III)-assisted signal amplification. In this study, the special structure of THMS was used to realize efficient fluorescence quenching and excellent signal unit transformation to complete the output of signal FAM. In the absence of Hg2+, hairpin probe (HP) containing thymine-rich (T-rich) ssDNA strand can induce the dissociation of the THMS, causing FAM far away from BHQ1 and increasing fluorescence intensity. Nevertheless, Hg2+ could bind to the thymine (T) base to form the dsDNA with T-Hg2+-T structure that stimulates Exo III to digest it from the blunt 3'-terminus to 5'-terminus, causing Hg2+ to be released from the dsDNA. The released Hg2+ could initiate the next cycling, allowing a large number of hairpin probes to be cleaved by Exo III to form ssDNA. These ssDNA could inhibit the switch dissociation of THMS, causing a dramatic decrease in the fluorescence signal. This allowed for the highly sensitive detection of Hg2+ at concentrations as low as 1.04 pM. In addition, the sensing showed a linear detection range of 0.01-50 nM and was used for the assay of Hg2+ in real samples of Xiangjiang river water and tap water. These results showed that the provided fluorescent sensing has a good application prospect in environmental and food monitoring.

Biodegradation of Terrigenous Organic Matter in a Stratified Large-Volume Water Column: Implications of the Removal of Terrigenous Organic Matter in the Coastal Ocean.

Large amounts of terrigenous organic matter (TOM) are delivered to the ocean every year. However, removal processes of TOM in the ocean are still poorly constrained. Here, we report results from a 339-day dark incubation experiment with a unique system holding a vertically stratified freshwater-seawater column. The quality and quantity of dissolved organic matter (DOM), RNA-based size-fraction microbial communities, and environmental factors were high-frequency-monitored. Microbial processes impacted TOM composition, including an increased DOM photobleaching rate with incubation time. The mixed layer had changed the bacterial community structure, diversity, and higher oxygen consumption rate. A two-end member modeling analysis suggested that estimated nutrient concentrations and prokaryotic abundance were lower, and total dissolved organic carbon was higher than that of the measured values. These results imply that DOM biodegradation was stimulated during freshwater-seawater mixing. In the bottom layer, fluorescent DOM components increased with the incubation time and were significantly positively related to highly unsaturated, oxygenated, and presumably aromatic compound molecular formulas. These results suggest that surfaced-derived TOM sinking leads to increased DOM transformation and likely results in carbon storage in the bottom water. Overall, these results suggest that microbial transforming TOM plays more important biogeochemical roles in estuaries and coastal oceans than what we know before.

Improved water quality monitoring indicators may increase carbon storage in the oceans.

Indicators related to organic matter are important when assessing aquatic environment quality. The chemical oxygen demand (COD) is widely used as a water quality reference. However, oxidizing agents used to determine the COD can oxidize refractory organic matter that is not pollutant and can persist in the ocean for thousands of years. This means the COD can misrepresent the water quality. The actual water quality can be indicated better by the biochemical oxygen demand (BOD) than the COD, but determining the BOD is time-consuming and gives variable results. In this study, the optical properties of dissolved organic matter in water samples from the Chinese coast that had been incubated for a long time or directly oxidized using COD oxidant were analyzed. The results indicated that the oxidizing agent rapidly oxidized 22.93% ± 4.96% of refractory dissolved organic matter (RDOM) that was resistant to microbial degradation, implying that RDOM made a marked contribution to the COD. Meanwhile, size-fractional fluorescence spectroscopy and COD measurements indicated that the COD of the >0.7 µm fraction and the fluorescence intensity of the protein-like component significantly positively correlated with the BOD of the bulk sample. This indicated that, for monitoring organic pollutants in coastal waters, the COD of the >0.7 µm fraction could be used as a proxy for the standard COD and that the fluorescence intensity of the protein-like component could be used as a convenient proxy for the BOD. The method can help retain recalcitrant organic matter in seawater to act as a carbon sink.

Heterogeneous viral contribution to dissolved organic matter processing in a long-term macrocosm experiment.

Viruses saturate environments throughout the world and play key roles in microbial food webs, yet how viral activities affect dissolved organic matter (DOM) processing in natural environments remains elusive. We established a large-scale long-term macrocosm experiment to explore viral dynamics and their potential impacts on microbial mortality and DOM quantity and quality in starved and stratified ecosystems. High viral infection dynamics and the virus-induced cell lysis (6.23-64.68% d-1) was found in the starved seawater macrocosm, which contributed to a significant transformation of microbial biomass into DOM (0.72-5.32 µg L-1 d-1). In the stratified macrocosm, a substantial amount of viral lysate DOM (2.43-17.87 µg L-1 d-1) was released into the upper riverine water, and viral lysis and DOM release (0.35-5.75 µg L-1 d-1) were reduced in the mixed water layer between riverine water and seawater. Viral lysis was stimulated at the bottom of stratified macrocosm, potentially fueled by the sinking of particulate organic carbon. Significant positive and negative associations between lytic viral production and different fluorescent DOM components were found in the starved and stratified macrocosm, indicating the potentially complex viral impacts on the production and utilization of DOM. Results also revealed the significant viral contribution to pools of both relatively higher molecular weight labile DOM and lower molecular weight recalcitrant DOM. Our study suggests that viruses have heterogeneous impact on the cycling and fate of DOM in aquatic environments.

Complexation and enantioselectivity of novel bridge-like uranyl- 2-((1Z,9Z)-9-(2-Hydroxyphenyl)-3,5,6,8-tetrahydrobenzo[h][1,4,7,10] dioxadiazacyclododecin-2-yl)-5-methoxyphenol with chiral organophosphorus pesticide enantiomers of R/S-malathions.

Designing new uranyl complexes with enantioselectivity is of great significance for the identification and separation of enantiomers of chiral pesticides. In this paper, a new asymmetric rigid uranyl-2-((1Z,9Z)-9-(2-Hydroxyphenyl)-3,5,6,8-tetrahydrobenzo[h][1,4,7,10] dioxadiaza-cyclododecin-2-yl)-5-methoxyphenol(Uranyl-HTDM) was designed, we used Uranyl-HTDM as a receptor to selectively coordinate with the guests of the chiral organophosphorus pesticide R/S-malathions(R/S-MLTs) to explore the receptor's enatioselectivity recognition of the chiral guests of R/S-MLTs. Density functional theory (DFT) method was used to comprehensively study the complexation mode of the receptor with enantiomers. The results showed that the U of Uranyl-HTDM could coordinate with both the thiophosphoryl sulfur and carbonyl oxygens of R/S-MLTs in different environments, respectively. The thermodynamics calculations further indicated that the receptor could selectively recognize the thiophosphoryl sulfur and carbonyl oxygen atoms of R/S-malathions, and the complexation abilities of Uranyl-HTDM to the R/S-malathions under different solvents were not the same. The smaller the polarity of solvents, the stronger the complexation ability of Uranyl-HTDM with R-malathion, toluene was an ideal solvent with large △G change and enatioselectivity coefficient of 99.55%. The study provides useful references for the design of new uranyl-salophens and for the experimental study on the molecular recognition of chiral organophosphorus pesticides.