Structural basis for phage-mediated activation and repression of bacterial DSR2 anti-phage defense system.

Silent information regulator 2 (Sir2) proteins typically catalyze NAD+-dependent protein deacetylation. The recently identified bacterial Sir2 domain-containing protein, defense-associated sirtuin 2 (DSR2), recognizes the phage tail tube and depletes NAD+ to abort phage propagation, which is counteracted by the phage-encoded DSR anti-defense 1 (DSAD1), but their molecular mechanisms remain unclear. Here, we determine cryo-EM structures of inactive DSR2 in its apo form, DSR2-DSAD1 and DSR2-DSAD1-NAD+, as well as active DSR2-tube and DSR2-tube-NAD+ complexes. DSR2 forms a tetramer with its C-terminal sensor domains (CTDs) in two distinct conformations: CTDclosed or CTDopen. Monomeric, rather than oligomeric, tail tube proteins preferentially bind to CTDclosed and activate Sir2 for NAD+ hydrolysis. DSAD1 binding to CTDopen allosterically inhibits tube binding and tube-mediated DSR2 activation. Our findings provide mechanistic insight into DSR2 assembly, tube-mediated DSR2 activation, and DSAD1-mediated inhibition and NAD+ substrate catalysis in bacterial DSR2 anti-phage defense systems.

Target ssDNA activates the NADase activity of prokaryotic SPARTA immune system.

Argonaute proteins (Agos), which use small RNAs or DNAs as guides to recognize complementary nucleic acid targets, mediate RNA silencing in eukaryotes. In prokaryotes, Agos are involved in immunity: the short prokaryotic Ago/TIR-APAZ (SPARTA) immune system triggers cell death by degrading NAD+ in response to invading plasmids, but its molecular mechanisms remain unknown. Here we used cryo-electron microscopy to determine the structures of inactive monomeric and active tetrameric Crenotalea thermophila SPARTA complexes, revealing mechanisms underlying SPARTA assembly, RNA-guided recognition of target single-stranded DNA (ssDNA) and subsequent SPARTA tetramerization, as well as tetramerization-dependent NADase activation. The small RNA guides Ago to recognize its ssDNA target, inducing SPARTA tetramerization via both Ago- and TIR-mediated interactions and resulting in a two-stranded, parallel, head-to-tail TIR rearrangement primed for NAD+ hydrolysis. Our findings thus identify the molecular basis for target ssDNA-mediated SPARTA activation, which will facilitate the development of SPARTA-based biotechnological tools.

Effect of green finance reform and innovation pilot zone on improving environmental pollution: an empirical evidence from Chinese cities.

Under the strategic deployment of dual carbon goals, China has entered the stage of high-quality development of low-carbon economic transformation. Green finance is an important tool to provide financing support for the development of green low-carbon projects and prevent environmental and climate financial risks. Whether and how it can help the implementation of the dual carbon goals is worth pondering and studying. Based on this background, this study considers the green finance reform and innovation pilot policy zone jointly issued by the Central People's Bank of China, National Development, and Reform Commission in 2017 as a natural experiment. Based on the panel data of 288 cities nationwide from 2010 to 2019, the effect of emission reduction is estimated using the PSM-DID method. The following conclusions are drawn: (1) The green finance policy has effectively improved the city's environmental quality, and the pilot effect of green finance has a certain lag on SO2 emissions and industrial smoke (dust) emissions; (2) the mechanism inspection shows that the policy mechanism has promoted the technological innovation level, sewage treatment capacity, and garbage harmless treatment capacity of the pilot area to a certain extent; and (3) the impact of green finance policy on environmental quality has regional and industrial characteristics heterogeneity. The green finance pilot policy in eastern and central regions will inhibit SO2 emissions, but the emission reduction effect in western regions is not significant; The implementation of the pilot policy of the green financial reform and innovation pilot zone has significantly reduced the sulfur dioxide emissions of the old industrial base cities, but the effect of the policy on non-old industrial bases is not obvious. The research conclusion has important enlightenment significance for further improving the construction of financial system, promoting the green transformation of regional industry, and improving the quality of urban environment.

Intermolecular interactions between starch and polyvinyl alcohol for improving mechanical properties of starch-based straws.

Starch/polyvinyl alcohol (PVA) degradable straws with different PVA contents were prepared by the twin-screw extrusion method. The results showed that the starch/PVA straws with 40 % PVA (PS4) had the highest dispersion uniformity of starch and PVA to achieve the best compatibility, and the compatibility size was below the micron level. Molecular interactions between starch and 40 % polyvinyl alcohol reached the highest due to the highest strength of hydrogen bonds, hence resulting in the highest texture densities. Consequently, the largest compatibility and molecular interactions significantly improved the mechanical properties and water resistance of PS4. Compared to the starch/PVA straw with 0 % PVA (PS0), swelling volume of PS4 decreased by 45.5 % (4 °C) and 65.2 % (70 °C), respectively. After soaking, the diameter strength increased by 540.1 % (4 °C, 1 h) and 638.7 % (70 °C, 15 min), respectively. Water absorption decreased by 45.3 % (4 °C, 30 min) and 27.6 % (70 °C, 30 min).

The Impact of Fintech Development on Air Pollution.

Over the past 40 years of reform and opening-up, China has achieved rapid economic and technological growth at the cost of severe air pollution. The emerging Fintech, as the result of financial institutions' adapting to the latest digital technology, might be a solution to reduce air pollution. This paper investigates the impact of Fintech development on air pollution using a two-factor fixed effects model based on data for prefecture-level cities in China from 2011 to 2017. The findings show that Fintech development can effectively reduce air pollution emissions, and this conclusion is proved to be robust throughout a series of tests. The mechanism analysis shows that Fintech reduces air pollution by promoting digital finance and green innovation.

Comparison of structural and functional properties of maize starch produced with commercial or endogenous enzymes.

To explore an effective and economic method to prepare higher contents of resistant starch (RS), different enzyme treatments including single pullulanase (PUL), commercial α-amylase (AA) or/and ß-amylase (BA) with PUL, and malt endogenous amylase (MA) with PUL were used and the structural, physicochemical properties and digestibility of all modified starches (MS) were compared. All the enzyme-treated starches displayed a mixture of B and V-type diffraction patterns. The MA/PUL-MS showed higher V-type diffraction peak intensity as compared to other modified starches. Compared to the combination of commercial enzyme treatment, the combination of malt enzyme treatment led to higher apparent amylose contents (45.56%), RS content (53.93%) and thermal stability (302 °C), whereas it possessed lower solubility indices and predicted glycaemic index. The apparent viscosity and shear resistance of MA/PUL-MS were lower than that of AA/PUL-MS, whereas that of MA/PUL-MS was higher than that of BA/PUL-MS and BA/AA/PUL-MS. These findings would provide a theoretical and applicative basis to produce foods with lower GI in industrial production.

Contagion in Global Stock Markets during the COVID-19 Crisis.

The impact of the coronavirus disease (COVID-19) outbreak on global stock markets is investigated by analyzing the impact of the COVID-19 pandemic on the stock markets of 15 countries selected from Asia, Europe, Latin America, and North America. Using extremal dependence tests of contagion, it is found that contagion effects are widespread to global equity markets in four regions. Latin America and North America are highly exposed to contagion risks, followed by Europe, with Asia being least vulnerable. Based on the time window of the crisis severity index, it is found that Latin America is most likely to be affected. The results confirm that for countries with more severe epidemics, there are stronger contagion effects. Therefore, for the governing authorities of various countries, if they want to prevent the contagion of financial crises during the pandemic, strong and timely epidemic prevention measures are very necessary.

Forecast and Analysis on Reducing China's CO2 Emissions from Lime Industrial Process.

China greenhouse gas inventories show that CO2 emissions from the lime industrial process are large scales and closely related to the development of its downstream industries. Therefore, there is high importance to analyze and forecast on reducing China's CO2 emissions from lime industrial process. The aims of this paper are to make up the research gaps in China and provide a quantitative reference for related authorities to formulate relevant policies. The prediction method in this paper is consistent with the published national inventory, which is an activity data based method to predict carbon dioxide emissions from the industrial process of four categories of lime products. Three future scenarios are assumed. The business as usual scenario (BAU) is a frozen scenario. There are two emission reduction scenarios (ERS and SRS) assumed under different emission reduction strength considering combined industrial process CO2 emission reduction approaches from both the production side and the consumption side. The results show that between 2020 and 2050, China's lime industrial process has an increasingly significant CO2 emission reduction potential, enabling both emission intensity reductions and total emission reductions to be achieved simultaneously. Based on the simulation results from emission reduction scenarios, compared with 2012 level, in 2050, the emission intensity can be reduced by 13⁻27%, the total lime production can be reduced by 49⁻78%, and the CO2 emissions in the lime industrial process can be reduced by 57⁻85%.

[Determination of dichlorvos in water by microwave-assisted-headspace-liquid-phase microextraction coupled with high performance liquid chromatography].

A novel method for the determination of dichlorvos in environmental water samples has been developed using microwave-assisted-headspace-liquid-phase microextraction (MAE-HS-LPME) coupled with high performance liquid chromatography (HPLC). The influences of extraction parameters in the sample matrix were investigated. Under optimized experimental conditions, the detection limit (S/N = 3), the quantification limit (S/N = 10) and the enrichment factor of the proposed method for the target analyte were 0.96 microg/L, 3.20 microg/L and 54, respectively. The recoveries of target analyte spiked in real water samples were 87.4%-103%. The extraction performance of MAE-HS-LPME to the target analyte was also compared with liquid-liquid extraction (LLE). The results indicated that the developed method is simple, rapid, efficient, solvent-saving, highly selective and widely applicable.