Competing C and N as Reactive Centers for Microsolvated Ambident Nucleophiles CN-(H2O)n=0-3: A Theoretical Study of E2/SN2 Reactions with CH3CH2X (X = Cl, Br, I).

As an ambident nucleophile, CN- has both C and N atoms that can act as the reactive center to facilitate substitution reactions. We investigate in detail the potential energy profiles of CN-(H2O)0-3 with CH3CH2X (X = Cl, Br, I) to explore the influence of solvent molecules on competition between the different nucleophilic atoms C and N involving the SN2 and E2 pathways. The energy barrier sequence for the transition states follows C@inv-SN2 < N@inv-SN2 < C@anti-E2 < N@anti-E2. When two different atoms act as nucleophilic atoms, the SN2 reaction is always preferred over the E2 reaction, and this preference increases with microsolvation. For the ambident nucleophiles CN-(H2O)0-3, C as the reactive center always has stronger nucleophilicity and basicity than N acting as the reactive center. Regarding the leaving group, the height of the energy barrier is positively correlated with the acidity of the CH3CH2X substrate for the E2 pathway and with X-heterolysis for the SN2 pathway. Furthermore, we found that in the gas phase, the energy barrier for different leaving group systems decreases gradually in the order Cl > Br > I, while in the SMD solution, the energy barrier and product energy increase slightly in the system from X = Cl to Br; this change may be due to the significantly weakened transition-state interaction for the X = Br system. Our activation strain, quantitative molecular orbital, and charge analyses reveal the physical mechanisms underlying the various computed trends. In addition, we also demonstrate the two points recently proposed by Vermeeren, P. . Chem. Eur. J. 2020, 26, 15538-15548.

Inactivation of fungal spores by performic acid in water: Comparisons with peracetic acid.

Performic acid (PFA) has received increasing attention in water disinfection due to its high disinfection efficiency and fewer formation of disinfection by-products. However, the inactivation of fungal spores by PFA has not been investigated. In this study, the results showed that the log-linear regression plus tail model adequately described the inactivation kinetic of fungal spores with PFA. The k values of A. niger and A. flavus with PFA were 0.36 min-1 and 0.07 min-1, respectively. Compared to peracetic acid, PFA was more efficient in inactivating fungal spores and caused more serious damage on cell membrane. Compared to neutral and alkaline conditions, acidic environments demonstrated a greater inactivation efficiency for PFA. The increase of PFA dosage and temperature had a promoting effect on the inactivation efficiency of fungal spores. PFA could kill the fungal spores by damaging cell membrane and penetration of cell membranes. In real water, the inactivation efficiency declined as a result of the existence of background substances such as dissolved organic matter. Moreover, the regrowth potential of fungal spores in R2A medium were severely inhibited after inactivation. This study provides some information for PFA to control fungi pollution and explores the mechanism of PFA inactivation.

Dynamics of nucleophilic substitution on ambident nucleophiles CN- and iodomethane: insights into the competition mechanism with neutral isomeric products.

Bimolecular nucleophilic substitution (SN2) plays a vital role in organic synthesis. Compared with nucleophiles with one reactive center, ambident nucleophiles can form isomer products. Determining the isomer branching ratios through experiments is difficult, and research on related dynamics characteristics is limited. This study uses dynamics trajectory simulations to explore the dynamics characteristics of the SN2 reaction of ambident nucleophiles CN- and CH3I. The calculated rate constants reproduce the experimental results at room temperature. The dynamics simulations reveal the mechanism of the competition between isomer products CH3CN and CH3NC with a ratio of 0.93 : 0.07. This mechanism is attributed to the height of the central barrier, which strongly stabilizes the transition state of the CH3CN product channel of the formed C-C bond. The product internal energy partitionings and the velocity scattering angle distributions are calculated based on the trajectory simulations, and are in almost agreement with the experimental results obtained at a low collision energy. The dynamics of the title reaction with the ambident nucleophile CN- are also compared with the SN2 dynamics of one reactive center F- and the substrate CH3Y (Y = Cl, I) reactions. This intensive review shows the competition of isomer products for the SN2 reaction of the ambident nucleophile CN- in the current study. This work provides unique insights into reaction selectivity for organic synthesis.

Identification, characteristics and rice growth promotion of a highly efficient cellulolytic bacterial strain, Cellulomonas iranensis ZJW-6, isolated from paddy soil in central China.

The microbial degradation of lignocellulose is the best way to treat straw, which has a broad application prospect. It is consistent with the idea of agricultural sustainable development and has an important impact on the utilization of biomass resources. To explore and utilize the microbial resources of lignocellulose degradation, 27 lignocellulose degrading strains were screened from 13 regions in China. ZJW-6 was selected because of its 49.6% lignocellulose weight loss rate. According to the theoretical analysis of the experimental results, the following straw degradation conditions were obtained by ZJW-6: nitrogen source input of 8.45 g/L, a pH of 8.57, and a temperature of 31.63°C, the maximum weight loss rate of rice straw could reach 54.8%. It was concluded that ZJW-6 belonged to Cellulomonas iranensis according to 16S rRNA-encoding gene sequence comparison and identification. ZJW-6 is a Gram-positive bacterium that grows slowly and has a small yellowish green colony. To explain the degradation mechanism of lignocellulose, the experiment of enzymatic properties of the strain was prepared and carried out. It was discovered that ZJW-6 has an excellent ability to degrade cellulose, hemicellulose, and lignin, with cellulose and hemicellulose loss rates reaching almost 50% in 4 days and lignin loss rates reaching nearly 30%. Furthermore, ZJW-6 demonstrated lignocellulose degradation under aerobic and anaerobic conditions, indicating the strain's broad application potential. ZJW-6 was found to be more effective than ordinary humic acid in improving rice soil (available phosphorus, available nitrogen, organic matter) and promoting rice growth in a rice pot experiment (increasing root-shoot ratio, root activity, chlorophyll content and net photosynthetic rate). ZJW-6 plays an important role in promoting the development and utilization of straw resources. It has important significance for the advancement of green agriculture.

A cross-scale study on the relationship between urban expansion and ecosystem services in China.

Clarifying the relationship between urban expansion and ecosystem services (ESs) is critical for sustainable management of land resources and ecosystems. However, little is known about the relationship between the two at the cross-scale (particularly at the national-provincial scale). Therefore, we conducted a systematic assessment of the spatiotemporal dynamics and the relationship between urban expansion and ESs including food production (FP), soil conservation (SC), carbon sequestration (CS), and water yield (WY) in China from 1992 to 2020 on the national-provincial scale. The results show that China's urban expansion took up a large amount of cropland, accounting for 79.35% of the newly-added built-up land. Shandong had the largest expansion scale and the highest speed, Shanghai had the most pronounced expansion intensity, and more than 50% of the provinces were dominated by outlying expansion pattern. In terms of total change, the three ESs of FP, SC, and WY increased by 286.5 × 106 t, 1893.61 × 106 t, and 8337.20 × 106 mm, respectively, and CS decreased by 683.90 × 106 Mg C. However, in the urban expansion area, FP and CS net decreased by 1757.6 × 104 t and 19,640.19 × 104 Mg C, respectively, while SC and WY net increased by 347.52 × 104 t and 20,264.11 × 104 mm, respectively. Shandong contributed the most to changes in ESs in urban expansion areas. Urban expansion was significantly negatively correlated with FP and CS with the correlation coefficients > -0.8; it was significantly positively correlated with SC and WY, with coefficients of 0.714 and 0.413, respectively, and urban expansion had a lagged effect on ESs. The impact of urban expansion on ESs had a spatial spillover effect and showed prominent spatial clustering in Anhui, Henan, and Shandong. Based on these results, we proposed urban planning countermeasures grounded in the perspective of ES improvement, which would provide policy references for the sustainable management of the ecological environment and land resources.

Differentiation of DNA or membrane damage of the cells in disinfection by flow cytometry.

Recently, the viabilities changes of fungal spores in the water supply system during different disinfection processes have been revealed. SYBR Green I (SG), a nucleic acid stain, its fluorescence intensity is correlated with the amount of double-stranded DNA. This study established a new method through successive SG-SG-PI staining (PI: Propidium Iodide) with flow cytometry (FCM). It could successfully distinguish DNA damage and membrane damage of fungal spores, clearly elucidating the intrinsic disinfection mechanism during the chemical disinfection. This method was briefly described as follows: firstly, (1) the fungal spores were stained with SG and washed by centrifugation; and then, (2) the washed spores were treated with disinfectants and terminated; after that, (3) the disinfected spores were re-stained with SG and analyzed by FCM; finally, (4) the SG re-stained spores were stained with PI and analyzed by FCM. The percentages of spores with DNA damage and membrane damage were determined by the fluorescence intensity obtained from steps (3) and (4), respectively. The repeatability and applicability of this developed method were confirmed. It was further applied to explore the inactivation mechanism during chlorine-based disinfection, and results demonstrated that chloramine attacked the DNA more seriously than the membrane, while chlorine and chlorine dioxide worked in a reverse way.

Comparative study on heterogeneous activation of peroxydisulfate and peroxymonosulfate with black carbon derived from coal tar residues: Contribution of free radical, 1O2 and surface-bound radicals.

Carbon materials draw increasing attention as metal-free catalysts for persulfates activation. Herein, the potential of black carbon (BC) derived from coal tar residues on heterogeneous activation of peroxydisulfate (PDS) and peroxymonosulfate (PMS) to eliminate organic pollutants was investigated. Compared with UV/persulfates systems, persulfates/BC systems degraded 3 selected phenolic compounds (i.e. phenol, 4-chlorophenol (4-CP) and bisphenol A (BPA)) with an order of magnitude higher oxidation rates, and removed dissolved organics (DOC) with over 27% higher efficiency. In the PDS/BC system, 1O2 and surface-bound radicals were proved to be the dominant active species, while free radicals, 1O2, and surface-bound radicals were responsible for organics oxidation in the PMS/BC system. Relative contribution of different reactive species in persulfates/BC systems was pH-dependent. Surface oxygen functionalities of BC were involved in 1O2 generation, and its structural defects played a critical role in forming free radicals and surface-bound radicals. This study provided an in-depth insight into carbon-driven persulfates activation processes.

Insight into the oxidation of phenolic pollutants by enhanced permanganate with biochar: The role of high-valent manganese intermediate species.

This work demonstrated that the oxidation of phenolic pollutants by permanganate (KMnO4) was effectively enhanced by a commercial biochar. Detailed characterization data indicated that the biochar contains porous structures, amounts of defective sites and abundant redox-active groups. In the presence of biochar, the degradation efficiency of 4-nitrophenol by KMnO4 surged from 5% to 92% in 180 min, up to 37.8% of total organic carbon (TOC) was removed. Meanwhile, acute toxicity of 4-nitrophenol was greatly reduced. Through analyzing oxidation products of triclosan (TCS) and using methyl phenyl sulfoxide (PMSO) as a chemical probe, high-valent Mn intermediates (i.e. Mn(VI)/Mn(V)) were proved to be the dominant oxidant in the KMnO4/biochar system. Quantitative structure-activity relationships (QSARs) were established between oxidation rate constants of various substituted phenols and classical descriptor variables (i.e., Hammett constant σ+). KMnO4/biochar was found to be less selective to the substituent variation of phenolic compounds compared with O3, K2FeO4, ClO2 and persulfate/carbon nanotube (PDS/CNT). This work provided a novel catalytic oxidation technology for eliminating phenolic compounds, and improved insights into the mechanistic study of the KMnO4-based oxidation process.

Straw biochar enhanced removal of heavy metal by ferrate.

This study demonstrated that As(III) was appreciably removed by ferrate in the presence of straw biochar. Removal efficiency of As in ferrate/biochar system was over 91%, increased by 34% compared with ferrate alone ([biochar]0 = 10 mg/L, [ferrate]0 = 6 mg/L, [As(III)]0 = 200 µg/L). In the reaction process, As(III) was oxidized to As(V) mainly by ferrate, while ferrate was reduced into ferric (hydr)oxides and coated on the biochar. Biochar was oxidized in the reaction and its surface area, pore volume and the amount of Lewis acid functional groups were substantially improved, which provided interaction sites for As adsorption. Analysis of hydrodynamic diameter and zeta potential revealed that biochar interacted with the ferrate resulted ferric oxides and enlarged the Fe-C-As particle/floc, which promoted their settlement and thus the liquid-solid separation of As. As(V) was adsorbed on the surface of biochar and ferric (hydr)oxides through hydrogen bond, electrostatic attraction and As-(OFe) bond. Ferrate/biochar was not only effective for As removal, but removed 73.31% of As, 50.38% of Cd, and 75.27% of Tl when these hazardous species synchronously existed in polluted water (initial content: As, 100 µg/L; Cd, 50 µg/L; Tl, 1 µg/L). The combination of ferrate with biochar has potential for the remediation of hazardous species polluted water.

Canopy Fibroblast Growth Factor Signaling Regulator 2 (CNPY2) Inhibits Neuron Apoptosis in Parkinson's Disease via the AKT/GSK3ß Pathway.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disorder caused by the progressive loss of dopaminergic neurons. Canopy fibroblast growth factor signaling regulator 2 (CNPY2) is down-regulated in this disease, but its functions are unknown. OBJECTIVE: This study investigates the effects and regulation of CNPY2 in the apoptosis of neurons in PD. METHODS: We established a PD model in vivo by a five consecutive days-injection of 1-methyl-4- phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) to mice. In vitro, the human SH-SY5Y neuroblastoma cells, after differentiation, were treated with 1-Methyl-4-phenylpyridinium iodide (MPP+) for modeling. The cells were transfected with a recombinant vector overexpressing CNPY2 followed by MPP+ treatment. Expression of CNPY2 and proteins related to apoptosis was detected by real-time PCR, western blot, or immunofluorescence staining. The ROS level and mitochondrial membrane potential were determined by flow cytometry. Cell viability and apoptosis were measured by MTT assay and TUNEL staining. RESULTS: CNPY2 level was down-regulated both in the brain and retina of PD mice and also inhibited in neurons by MPP+ in vitro. Overexpression of CNPY2 repressed the level of Bax and cleaved caspase-3, enhanced Bcl-2 level, and promoted neurite length under MPP+ treatment. CNPY2 overexpression reduced the accumulation of ROS and mitochondria dysfunction in neurons. The AKT/ GSK3ß signaling pathway was activated by overexpressed CNPY2 to inhibit MPP+-induced neuronal apoptosis, which was confirmed using an AKT inhibitor MK-2206 2HCl. CONCLUSION: CNPY2 alleviates oxidative stress, mitochondria dysfunction, and apoptosis of neurons induced by MPP+ by activating the AKT/ GSK3ß signaling pathway.

Heterogeneous catalytic ozonation of atrazine with Mn-loaded and Fe-loaded biochar.

After reaction with permanganate or ferrate, the resulted Mn-loaded and Fe-loaded biochar (MnOx/biochar and FeOx/biochar) exhibited excellent catalytic ozonation activity. O3 (2.5 mg/L) eliminated 48% of atrazine (ATZ, 5 µM) within 30 min at pH 7.0, while under identical conditions, ozonation efficiency of ATZ increased to 83% and 100% in MnOx/biochar and FeOx/biochar (20 mg/L) heterogeneous catalytic systems, respectively. Radical scavenger experiment and electron paramagnetic resonance (EPR) analysis confirmed that hydroxyl radical (•OH) was the dominant oxidant. Total Lewis acid sites on MnOx/biochar and FeOx/biochar were 3.5 and 4.1 times of that on the raw biochar, which induced enhanced adsorption of O3 and its subsequent decomposition into •OH. Electron transfer via redox pairs on MnOx/biochar and FeOx/biochar was observed by cyclic voltammetry scans, which also functioned in the improved catalytic capacity. Degradation pathways of ATZ in MnOx/biochar and FeOx/biochar ozonation systems were proposed, with 34.6% and 44.8% of dechlorination effect accomplished within 30 min of reaction, which was improved by 4.1 and 5.3 times compared to pure ozonation. After 12-hour treatment, acute toxicity of ATZ oxidation products was reduced from 38.3% of pure ozonation system to 14.5% and 6.3% of activated ozonation systems with MnOx/biochar and FeOx/biochar, respectively. Mn-loaded biochar and Fe-loaded biochar have great potential for heterogeneous catalytic ozonation of polluted water.

Global patterns and changes of carbon emissions from land use during 1992-2015.

Carbon emissions from land use (E LUC) are an important part of anthropogenic CO2 emissions, but its size and location remain uncertain, and our knowledge of the relationship between E LUC and GDP remains partial. We showed that the carbon emissions directly caused by land use change (direct E LUC) during 1992-2015 was 26.54 Pg C (1.15 Pg C yr-1), with a decreased trend and a net reduction rate of -0.15 Pg C yr-1. The areas that exhibited reductions were concentrated in South America, Central Africa, and Southeast Asia, and those with increments were scattered in Northwestern North America, Eastern South America, Central Africa, East Asia, and parts of Southeast Asia. For the indirect carbon emissions from the utilization of built-up land (indirect E LUC), it manifested an upward trend with a total emission of 27.51 Pg C (1.2 Pg C yr-1). The total value resulted by global E LUC was $136.3 × 109 US, and the value of annual was equivalent to 3.7 times the GDP of the Central African Republic in 2015 ($5.93 × 109 US yr-1). Among the 79 countries and regions considered in this study, 54 represented the upward GDP with increased emissions, and only 25 experienced GDP growth with emission reductions. These findings highlight the pivotal role of land use change in the carbon cycle and the significance of coordinated development between GDP and carbon emissions.

Degradation of organic pollutants by ferrate/biochar: Enhanced formation of strong intermediate oxidative iron species.

Biochar draws increasing attention as soil amendment, carbon sink, slow-release fertilizer, and adsorbent. Herein, it was interesting to find out that among 11 kinds of commercial biochar, 3 of them facilitated ferrate oxidation of sulfamethoxazole (SMX). With the addition of biochar, oxidation rates of 5 kinds of organic pollutants (including antibiotics, pharmaceuticals, and personal care product) increased by 3-14 times, and the total organic carbon (TOC) removal ratio increased by 2.4-8 times. Radical scavenging experiment, electron spin resonance (ESR) analysis, and probe compound (sulfoxide) oxidation experiment showed that no radical but intermediate iron species [Fe(IV) and Fe(V)] participated in the oxidation reactions. Redox-active moieties (phenolic hydroxyl) on biochar interact with ferrate as electron shuttle and enhance the formation of intermediate iron species through electron transfer. The intermediate iron species not only interacted with organic pollutants and accelerated their transformation, but also corrupted (oxidized) the physical structure of biochar and expanded its surface area and pore volume. Increase of surface area and pore volume of the spent biochar in turn resulted in the improved adsorption capacity. In addition to eliminating emerging organic pollutants, ferrate/biochar removed 8.7%-31.6% of TOC in authentic water and decreased the formation potential of 20 kinds of chlorinated disinfection by-products (DBPs) by 9.2%-23.9%.

Ecological security and health risk assessment of soil heavy metals on a village-level scale, based on different land use types.

Land use affects the accumulation of heavy metals in soil, which will endanger ecological safety and human health. Taking the village as an administrative unit, the ecological safety and health risks of heavy metals, namely, Cr, Cu, Zn, and Pb in soils in the Houzhai River Watershed of Guizhou Province, China, were evaluated based on land use types by the Hakanson potential ecological risk methods and human health risk model. Results showed that the spatial heterogeneity of Cu and Zn was greatly affected by primary structural factors, and Cr and Pb were interfered by both structural factors and human activities. The geo-accumulation index of the heavy metals showed a light pollution in the study area. The comprehensive potential ecological risk of heavy metal in the area was divided into three levels: slight, moderate, and intense, and it is spatially high in the northwest and low in the southeast. Both non-carcinogenic risk and carcinogenic risk of the heavy metals to the human body are not significant and are acceptable. The risks of children are higher than adults, and direct intake is the primary route of exposure in the area. The potential ecological risk and human health risk of soil heavy metals are relatively obviously affected by digital elevation data and normalized vegetation index. The study has certain reference value for the prevention and control of regional soil heavy metal risk.

Enhanced Permanganate Oxidation of Sulfamethoxazole and Removal of Dissolved Organics with Biochar: Formation of Highly Oxidative Manganese Intermediate Species and in Situ Activation of Biochar.

Sulfamethoxazole (SMX) is a broad-spectrum antibiotic and was largely used in breeding industry. The reaction rate of SMX with KMnO4 is slow, and the adsorption efficiency of biochar for SMX was inferior (less than 11% in 30 min). By adding biochar powder into SMX solution with the addition of permanganate, the oxidation ratio of SMX surged to 97% in 30 min, and over 58% of the total organic carbon (TOC) was simultaneously removed. KMnO4 interacted with biochar and resulted in the formation of highly oxidative intermediate manganese species, which transformed SMX into hydrolysis products, oxygen-transfer products, and self-coupling products. Brunauer-Emmett-Teller (BET) analysis showed that surface area, total pore volume, and micropore volume of biochar increased by 32.1%, 36.4%, and 80.6%, respectively, after reaction process. This in situ activation of biochar with KMnO4 enhanced its adsorption capacity and led to great improvement of TOC removal. Besides KMnO4 oxidation, biochar also enhanced TOC removal in Mn(III) oxidation (KMnO4+ bisulfite) and ozonization of SMX. Considering that KMnO4 could react with biochar and result in the formation of intermediate manganese species, while biochar can be simultaneously activated and exhibit high capacity for organic adsorption, the combination of biochar with the chemical/advanced oxidation could be a promising process for the removal of environmental pollutants.