Test of Light-Lepton Universality in the Rates of Inclusive Semileptonic B-Meson Decays at Belle II

We present the first measurement of the ratio of branching fractions of inclusive semileptonic B-meson decays, R(X_{e/μ})=B(B→Xeν)/B(B→Xμν), a precision test of electron-muon universality, using data corresponding to 189  fb^{-1} from electron-positron collisions collected with the Belle II detector. In events where the partner B meson is fully reconstructed, we use fits to the lepton momentum spectra above 1.3  GeV/c to obtain R(X_{e/μ})=1.007±0.009(stat)±0.019(syst), which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation.

Postoperative pulmonary complications in older patients undergoing elective surgery with a supraglottic airway device or tracheal intubation

The two most commonly used airway management techniques during general anaesthesia are supraglottic airway devices and tracheal tubes. In older patients undergoing elective non-cardiothoracic surgery under general anaesthesia with positive pressure ventilation, we hypothesised that a composite measure of in-hospital postoperative pulmonary complications would be less frequent when a supraglottic airway device was used compared with a tracheal tube. We studied patients aged ≥ 70 years in 17 clinical centres. Patients were allocated randomly to airway management with a supraglottic airway device or a tracheal tube. Between August 2016 and April 2020, 2900 patients were studied, of whom 2751 were included in the primary analysis (1387 with supraglottic airway device and 1364 with a tracheal tube). Pre-operatively, 2431 (88.4%) patients were estimated to have a postoperative pulmonary complication risk index of 1-2. Postoperative pulmonary complications, mostly coughing, occurred in 270 of 1387 patients (19.5%) allocated to a supraglottic airway device and 342 of 1364 patients (25.1%) assigned to a tracheal tube (absolute difference -5.6% (95%CI -8.7 to -2.5), risk ratio 0.78 (95%CI 0.67-0.89); p < 0.001). Among otherwise healthy older patients undergoing elective surgery under general anaesthesia with intra-operative positive pressure ventilation of their lungs, there were fewer postoperative pulmonary complications when the airway was managed with a supraglottic airway device compared with a tracheal tube.

The role of IL-6, IL-10, TNF-α and PD-1 expression on CD4 T cells in atrial fibrillation

Backgrounds

While not completely understood, the electrical, structural, and communication pathways that play a role in the onset and progression of atrial fibrillation (AF) seem to be connected to the intricate interplay between neurohormones and cellular mediators. Our study's objective was to examine how the expression profiles of the inflammatory cytokines interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor (TNF), and programmed death 1 (PD-1) changed in Cluster of Differentiation 4 (CD4) T cells depending on whether atrial fibrillation was paroxysmal or permanent. This analysis would provide new diagnostic markers for the detection and management of atrial fibrillation.

Methods

In a cross-sectional study, 60 healthy controls, 49 patients with persistent atrial fibrillation, and 50 patients with paroxysmal atrial fibrillation were compared. Serum biomarker levels are found using the ELISA method, which uses enzyme-linked immunosorbent assay. Echocardiography was used to assess heart function.

Results

Patients with atrial fibrillation had serum concentrations of IL-6, TNF-a, and IL-10 that were considerably higher than but PD-1 was lower those in the non-AF control group and those in patients with persistent atrial fibrillation. According to the diameter of LA and the serum level of NT-proB-type natriuretic peptide (NT-proBNP) is greater than that of patients with paroxysmal atrial fibrillation than control group. Patients with persistent atrial fibrillation had increased serum levels of low-density lipoprotein cholesterol (LDL-C) compared with those without atrial fibrillation. While PD-1 in patients with paroxysmal atrial fibrillation is closely related to C-reactive protein (CRP), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and very low density lipoprotein cholesterol. In addition, PD-1 in patients with persistent atrial fibrillation is closely related to IL-6, TNF-a, and IL-10.

Conclusion

Higher blood concentrations of NT-proBNP, IL-6, IL-10, TNF-, and LDL-C but low level of PD-1 are associated with progression from paroxysmal or chronic AF.

Irpex lacteus polysaccharide exhibits therapeutic potential for ovarian fibrosis in PCOS rats via the TGF-β1/smad pathway

Polycystic ovarian syndrome (PCOS) is one of the commonest endocrinopathies in childbearing women. The research was conducted to assess the impact of Irpex lacteus polysaccharide (ILP, 1000 mg/kg) on the letrozole (1 mg/kg)-induced PCOS model in female rats. Metformin (Met, 265 mg/kg) as the positive control. The study suggested that ILP restored the estrous cycle in rats with PCOS as well as lowered relative ovarian weight and body weight, in comparison to normal. Rats with PCOS showed improvement in ovarian structure and fibrosis when given ILP. ILP decreased the testosterone (T), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), total cholesterol (TC), luteinizing hormone (LH), homeostasis model assessment-insulin resistance (HOMA-IR), fasting blood glucose (FBG), and insulin (INS) levels and elevated the follicle-stimulating hormone (FSH) and estrogen (E2) levels in PCOS rats. In addition, ILP increased the content of superoxide dismutase (SOD) in serum and the antioxidant enzymes (Prdx3, Sod1, Gsr, Gsta4, Mgst1, Gpx3, Sod2 and Cat) expression levels in the ovaries and decreased the serum expression of malondialdehyde (MDA). In addition, ILP treatment slowed down the process of the fibrosis-associated TGF-β1/Smad pathway and downregulated α-smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF) levels in PCOS rats ovaries. According to these findings, ILP may be able to treat letrozole-induced PCOS in rats by ameliorating metabolic disturbances, sex hormone levels, oxidative stress, and ovarian fibrosis.

Multiplex modification of Yarrowia lipolytica for enhanced erythritol biosynthesis from glycerol through modularized metabolic engineering

Erythritol is a novelty 4-carbon sugar polyol and has great potential to be used as the precursor of some platform chemicals. The increasing cost of glucose poses researchers shifting insights to the cheaper biodiesel raw materials. Herein, we engineered a non-degradation, non-byproducts Yarrowia lipolytica for the erythritol production with high-titer from glycerol. Initially, the degradation and competition modules were blocked by URA3 counter-selection marker. Subsequently, a shortened biosynthetic pathway was explored to elevate its synthetic flux by multi-modules combination expression of functional genes. Furthermore, a screened glycerol transporter ScFPS1 was integrated into ERY6 genome to promote the glycerol uptake. The constructed strain ERY8 produced 176.66 g/L erythritol in the 5-L bioreactor with a yield and productivity of 0.631 g/g and 1.23 g/L/h, respectively, which achieved the highest fermentation production efficiency till date. This study proposed a novel multi-modules combination strategy for effectively engineering Y. lipolytica to produce erythritol using glycerol.

Computer-aided design of novel cellobiose 2-epimerase for efficient synthesis of lactulose using lactose

Cellobiose 2-epimerase (CE) is ideally suited to synthesize lactulose from lactose, but the poor thermostability and catalytic efficiency restrict enzymatic application. Herein, a non-characterized CE originating from Caldicellulosiruptor morganii (CmCE) was discovered in the NCBI database. Then, a smart mutation library was constructed based on FoldX ΔΔG calculation and modeling structure analysis, from which a positive mutant D226G located within the α₈/α₉ loop exhibited longer half-lives at 65-75 °C as well as lower K_m and higher k_cat/K_m values compared with CmCE. Molecular modeling demonstrated that the improvement of D226G was largely attributed to the rigidification of the flexible loop, the compactness of the catalysis pocket and the increment of substrate-binding capability. Finally, the yield of synthesizing lactulose catalyzed by D226G reached 45.5%, higher than the 35.9% achieved with CmCE. The disclosed effect of the flexible loop on enzymatic stability and catalysis provides insight to redesign efficient CEs to biosynthesize lactulose.

Revisiting the critical roles of reactive astrocytes in neurodegeneration

Astrocytes, an integral component of the central nervous system (CNS), contribute to the maintenance of physiological homeostasis through their roles in synaptic function, K+ buffering, blood-brain barrier (BBB) maintenance, and neuronal metabolism. Reactive astrocytes refer to astrocytes undergoing morphological, molecular and functional remodelling in response to pathological stimuli. The activation and differentiation of astrocytes are implicated in the pathogenesis of multiple neurodegenerative diseases. However, there are still controversies regarding their subset identification, function and nomenclature in neurodegeneration. In this review, we revisit the multidimensional roles of reactive astrocytes in Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). Furthermore, we propose a precise linkage between astrocyte subsets and their functions based on single-cell sequencing analyses.

The transcription factor XBP1 in dendritic cells promotes the TH2 cell response in airway allergy

Dendritic cells (DCs) that express T cell immunoglobulin domain molecule-4 (TIM4), a cell surface receptor for phosphatidylserine, induce T helper 2 (T_H2) cell responses and allergic reactions. We elucidated the role of the transcription factor X-box-binding protein-1 (XBP1) in the induction of the T_H2 cell response through its role in generating TIM4⁺ DCs. We found that XBP1 was required for TIM4 mRNA and protein expression in airway DCs in response to the cytokine interleukin-2 (IL-2) and that this pathway was required for TIM4 expression on DCs in response to the allergens PM2.5 and Derf1. The IL-2-XBP1-TIM4 axis in DCs contributed to Derf1/PM2.5-induced, aberrant T_H2 cell responses in vivo. An interaction between the guanine nucleotide exchange factor Son of sevenless-1 (SOS1) and the GTPase RAS promoted XBP1 and TIM4 production in DCs. Targeting the XBP1-TIM4 pathway in DCs prevented or alleviated experimental airway allergy. Together, these data suggest that XBP1 is required for T_H2 cell responses by inducing the development of TIM4⁺ DCs, which depends on the IL-2-XBP1-SOS1 axis. This signaling pathway provides potential therapeutic targets for the treatment of T_H2 cell-dependent inflammation or allergic diseases.

First Study of Reaction Ξ^{0}n→Ξ^{-}p Using Ξ^{0}-Nucleus Scattering at an Electron-Positron Collider

Using (1.0087±0.0044)×10^{10}  J/ψ events collected with the BESIII detector at the BEPCII storage ring, the process Ξ^{0}n→Ξ^{-}p is studied, where the Ξ^{0} baryon is produced in the process J/ψ→Ξ^{0}Ξ[over ¯]^{0} and the neutron is a component of the ^{9}Be, ^{12}C, and ^{197}Au nuclei in the beam pipe. A clear signal is observed with a statistical significance of 7.1σ. The cross section of the reaction Ξ^{0}+^{9}Be→Ξ^{-}+p+^{8}Be is determined to be σ(Ξ^{0}+^{9}Be→Ξ^{-}+p+^{8}Be)=(22.1±5.3_{stat}±4.5_{sys})  mb at the Ξ^{0} momentum of 0.818  GeV/c, where the first uncertainty is statistical and the second is systematic. No significant H-dibaryon signal is observed in the Ξ^{-}p final state. This is the first study of hyperon-nucleon interactions in electron-positron collisions and opens up a new direction for such research.

[Estimate the population size of transgender women based on the capture-recapture method in Tianjin]

Objective: To investigate the population size of transgender women (TGW) in Tianjin and analyze the characteristics of their sexual behaviors to provide a basis for AIDS prevention and control. Methods: To estimate the population size of TGW in Tianjin using the capture-recapture method. At the same time, an anonymous questionnaire was collected to conduct a multi-factor logistic analysis of the TGW population's sexual behavior. Results: A total of 213 TGW were investigated. Tianjin's estimated TGW population size was 599 (95%CI: 407-792). Multivariate logistic analysis of the use of condoms consistently showed that compared with TGW without regular sex partners, those with regular sex partners had a lower proportion of consistent condom use (aOR=0.44, 95%CI: 0.23-0.82) and had received HIV tests in the last year were more likely to adhere to condom use than those who had not been tested (aOR=2.73, 95%CI: 1.06-6.99). Conclusion: It is necessary to strengthen HIV mobilization testing among the TGW population and their regular sexual partners to improve condom use.

Measurements of Normalized Differential Cross Sections of Inclusive π^{0} and K_{S}^{0} Production in e^{+}e^{-} Annihilation at Energies from 2.2324 to 3.6710 GeV

Based on electron positron collision data collected with the BESIII detector operating at the BEPCII storage rings, the differential cross sections of inclusive π^{0} and K_{S}^{0} production as a function of hadron momentum, normalized by the total cross section of the e^{+}e^{-}→hadrons process, are measured at six center-of-mass energies from 2.2324 to 3.6710 GeV. Our results, which cover a relative hadron energy range from 0.1 to 0.9, significantly deviate from several theoretical calculations based on existing fragmentation functions.

Metabolic engineering and pathway construction for O-acetyl-L-homoserine production in Escherichia coli

O-Acetyl-L-homoserine (OAH) is a potentially important platform metabolic intermediate for the production of homoserine lactone, methionine, 1,4-butanediol and 1,3-propanediol which have giant market value. Currently, multiple strategies have been adopted to explore sustainable production of OAH. However, the production of OAH by consuming cheap bio-based feedstocks with Escherichia coli as the chassis is still in its infancy. Construction of high yield OAH-producing strains is of great significance in industry. In this study, we introduced an exogenous metA from Bacillus cereus (metXbc) and engineered an OAH-producing strain by combinatorial metabolic engineering. Initially, exogenous metXs/metA were screened and used to reconstruct an initial biosynthesis pathway of OAH in E. coli. Subsequently, the disruption of degradation and competitive pathways combined with optimal expression of metXbc were carried out, accumulating 5.47 g/L OAH. Meanwhile, the homoserine pool was enriched by overexpressing metL with producing 7.42 g/L OAH. Lastly, the carbon flux of central carbon metabolism was redistributed to balance the metabolic flux of homoserine and acetyl coenzyme A (acetyl-CoA) in OAH biosynthesis with accumulating 8.29 g/L OAH. The engineered strain produced 24.33 g/L OAH with a yield of 0.23 g/g glucose in fed-batch fermentation. By these strategies, the key nodes for OAH synthesis were clarified and corresponding strategies were proposed. This study would lay a foundation for OAH bioproduction.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03564-5.

Thorough research and modification of one-carbon units cycle for improving L-methionine production in Escherichia coli

Methionine is the only one of the essential amino acids that contain sulfur, widely used as a feed additive in agriculture. In this study, the availability of 5-methyl-tetrahydrofolate was confirmed as the main limitation in the complex multibranched biosynthetic pathway of L-methionine. The cycle of one-carbon units was thoroughly investigated and modified to supply 5-methyl-tetrahydrofolate for L-methionine production, such as enhancing the supply of precursor, expediting the conversion rate of the cycle, introducing exogenous serine hydroxymethyltransferase and increasing pool size of one-carbon units carrier. The final strain MYA/pAmFA-4 was able to produce 20.89 g/L L-methionine by fed-batch fermentation, which was the highest titer reported in the literatures. This study is instructive for other metabolites biosynthesized needing one-carbon units or having a complex multibranched biosynthetic pathway.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03625-9.

Investigation of the enhancement for Echinocandin B fermentation with methyl oleate from transcription level

Echinocandin B (ECB) is the key precursor compound of the antifungal drug Anidulafungin. The effects of the five precursor amino acids on ECB biosynthesis were firstly investigated. It showed that although L-threonine was a main compound of the hexapeptide scaffold of ECB, exogenous addition of L-threonine had no significant effect on the increase of ECB fermentation titer. Meanwhile, the ECB fermentation titer with methyl oleate showed two times higher than that of the other carbon sources. Transcription level analysis of the key genes for ECB biosynthesis indicated that the gene an655543 related to L-threonine biosynthesis showed higher value during the fermentation process, therefore, the exogenous addition of L-threonine had no obvious affection. Furthermore, it indicated that the transcription level of gene ecdA might be the main restriction factor for the ECB biosynthesis. The study provided the research foundation for the modification of the ECB producing strains in the following work.

Precision Measurement of the Decay Σ^{+}→pγ in the Process J/ψ→Σ^{+}Σ[over ¯]^{-}

Using (10 087±44)×10^{6} J/ψ events collected with the BESIII detector, the radiative hyperon decay Σ^{+}→pγ is studied at an electron-positron collider experiment for the first time. The absolute branching fraction is measured to be (0.996±0.021_{stat}±0.018_{syst})×10^{-3}, which is lower than its world average value by 4.2 standard deviations. Its decay asymmetry parameter is determined to be -0.652±0.056_{stat}±0.020_{syst}. The branching fraction and decay asymmetry parameter are the most precise to date, and the accuracies are improved by 78% and 34%, respectively.

Tau pathology epigenetically remodels the neuron-glial cross-talk in Alzheimer's disease

The neuron-glia cross-talk is critical to brain homeostasis and is particularly affected by neurodegenerative diseases. How neurons manipulate the neuron-astrocyte interaction under pathological conditions, such as hyperphosphorylated tau, a pathological hallmark in Alzheimer's disease (AD), remains elusive. In this study, we identified excessively elevated neuronal expression of adenosine receptor 1 (Adora1 or A1R) in 3×Tg mice, MAPT P301L (rTg4510) mice, patients with AD, and patient-derived neurons. The up-regulation of A1R was found to be tau pathology dependent and posttranscriptionally regulated by Mef2c via miR-133a-3p. Rebuilding the miR-133a-3p/A1R signal effectively rescued synaptic and memory impairments in AD mice. Furthermore, neuronal A1R promoted the release of lipocalin 2 (Lcn2) and resulted in astrocyte activation. Last, silencing neuronal Lcn2 in AD mice ameliorated astrocyte activation and restored synaptic plasticity and learning/memory. Our findings reveal that the tau pathology remodels neuron-glial cross-talk and promotes neurodegenerative progression. Approaches targeting A1R and modulating this signaling pathway might be a potential therapeutic strategy for AD.

Measurements of the Electric and Magnetic Form Factors of the Neutron for Timelike Momentum Transfer

We present the first measurements of the electric and magnetic form factors of the neutron in the timelike (positive q^{2}) region as function of four-momentum transfer. We explored the differential cross sections of the reaction e^{+}e^{-}→n[over ¯]n with data collected with the BESIII detector at the BEPCII accelerator, corresponding to an integrated luminosity of 354.6  pb^{-1} in total at twelve center-of-mass energies between sqrt[s]=2.0-2.95  GeV. A relative uncertainty of 18% and 12% for the electric and magnetic form factors, respectively, is achieved at sqrt[s]=2.3935  GeV. Our results are comparable in accuracy to those from electron scattering in the comparable spacelike region of four-momentum transfer. The electromagnetic form factor ratio R_{em}≡|G_{E}|/|G_{M}| is within the uncertainties close to unity. We compare our result on |G_{E}| and |G_{M}| to recent model predictions, and the measurements in the spacelike region to test the analyticity of electromagnetic form factors.

Observation of a New X(3872) Production Process e^{+}e^{-}→ωX(3872)

Using 4.7  fb^{-1} of e^{+}e^{-} collision data at center-of-mass energies from 4.661 to 4.951 GeV collected by the BESIII detector at the BEPCII collider, we observe the X(3872) production process e^{+}e^{-}→ωX(3872) for the first time. The significance is 7.8σ, including both the statistical and systematic uncertainties. The e^{+}e^{-}→ωX(3872) Born cross section and the corresponding upper limit at 90% confidence level at each energy point are reported. The line shape of the cross section indicates that the ωX(3872) signals may be from the decays of some nontrivial structures.

Construction of exogenous methanol, formate, and betaine modules for methyl donor supply in methionine biosynthesis

Methionine is an essential sulfur-containing amino acid that finds widespread applications in agriculture, medicine, and the food industry. However, the complex and multibranched biosynthetic pathway of methionine has posed significant challenges to its efficient fermentation production. In this study, we employed a modularized synthetic biology strategy to improve the weakest branched pathway of methionine biosynthesis. Three exogenous modules were constructed and assembled to provide methyl donors, which are the primary limiting factors in methionine biosynthesis. The first module utilized added methanol, which was converted into 5,10-methylene-tetrahydrofolate for methionine production but was hindered by the toxicity of methanol. To circumvent this issue, a non-toxic formate module was constructed, resulting in a visible improvement in the methionine titer. Finally, an exogenous betaine module was constructed, which could directly deliver methyl to methionine. The final strain produced 2.87 g/L of methionine in a flask, representing a 20% increase over the starting strain. This study presents a novel strategy for improving and balancing other metabolites that are synthesized through complex multibranched pathways.

Observation of Three Charmoniumlike States with J^{PC}=1^{--} in e^{+}e^{-}→D^{*0}D^{*-}π^{+}

The Born cross sections of the process e^{+}e^{-}→D^{*0}D^{*-}π^{+} at center-of-mass energies from 4.189 to 4.951 GeV are measured for the first time. The data samples used correspond to an integrated luminosity of 17.9  fb^{-1} and were collected by the BESIII detector operating at the BEPCII storage ring. Three enhancements around 4.20, 4.47, and 4.67 GeV are visible. The resonances have masses of 4209.6±4.7±5.9  MeV/c^{2}, 4469.1±26.2±3.6  MeV/c^{2}, and 4675.3±29.5±3.5  MeV/c^{2} and widths of 81.6±17.8±9.0  MeV, 246.3±36.7±9.4  MeV, and 218.3±72.9±9.3  MeV, respectively, where the first uncertainties are statistical and the second systematic. The first and third resonances are consistent with the ψ(4230) and ψ(4660) states, respectively, while the second one is compatible with the ψ(4500) observed in the e^{+}e^{-}→K^{+}K^{-}J/ψ process. These three charmoniumlike ψ states are observed in the e^{+}e^{-}→D^{*0}D^{*-}π^{+} process for the first time.

Tuning an efficient Escherichia coli whole-cell catalyst expressing l-pantolactone dehydrogenase for the biosynthesis of d-(-)-pantolactone

d-(-)-Pantolactone (DPL) is a key intermediate for the production of d-(+)-pantothenate (vitamin B5). Deracemization of d,l-pantolactone (D,L-PL) through oxidizing l-(+)-pantolactone (LPL) to ketopantoyl lactone (KPL) and subsequently reducing KPL to DPL is a promising route for synthesizing DPL. Herein, a newly mined l-pantolactone dehydrogenase from Rhodococcus hoagie (RhoLPLDH) was used for the oxidative dehydrogenation of LPL. To alleviate inclusion bodies formed by membrane-bound RhoLPLDH intracellular expression in E. coli, strategies involving chaperone assistance and decreasing induction temperature were used to achieve RhoLPLDH soluble expression. To enhance its activity, directed evolution and hydrophilicity-based engineering yielded increased catalytic activity and thermostability. 1M LPL was efficiently converted to KPL by engineering strain CM5 co-expressing RhoLPLDH^{L254I/V241I/I156L/F224Q/N164K} and chaperone. A "two stages in one-pot" method was employed in deracemization of 1M D,L-PL with 91.2% yield. These results demonstrated that CM5 catalyst exhibits great potential in enzyme cascade deracemization for the production of DPL.

Improving ATP availability by sod1 deletion with a strategy of precursor feeding enhanced S-adenosyl-L-methionine accumulation in Saccharomyces cerevisiae

S-adenosyl-L-methionine (SAM), used in diverse pharmaceutical applications, was biosynthesized from L-methionine (L-met) and adenosine triphosphate (ATP). This study aims to increase the accumulation of SAM in Saccharomyces cerevisiae by promoting ATP availability. Strain ΔSOD1 was obtained from the parent strain WT15-33 (CCTCC M 2021915) by deleting gene sod1, which improved the supply of ATP. The SAM content in strain ΔSOD1 exhibited a 22.3% improvement compared to the parent strain, which reached 93.6 mg g^-1. The transformation of NADH (reduced nicotinamide adenine dinucleotide) and the relative expression of ATPase essential genes were investigated, respectively. The results showed that the lack of gene sod1 benefited the generation of ATP, which positively regulated the synthesis of SAM. Besides that, the production of SAM was further enhanced by improving substrate assimilation. With the infusion of 1.44 g L^-1L-met and 0.60 g L^-1 adenosine at 24 h (h) and 0 h following fermentation, the optimum medium could produce 1.54 g L^-1 SAM. Based on the regulations mentioned above, the SAM concentration of strain ΔSOD1 enhanced from 7.3 g L^-1 to 10.1 g L^-1 in a 5-L fermenter in 118 h. This work introduces a novel idea for the biosynthesis of ATP and SAM, and the strain ΔSOD1 has the potential for industrial production.

Improving the catalytic activity of β-glucosidase from Coniophora puteana via semi-rational design for efficient biomass cellulose degradation

In order to improve the degradation activity of β-glucosidase (CpBgl) from Coniophora puteana, the structural modification was conducted. The enzyme activity of mutants CpBgl-Q20C and CpBgl-A240S was increased by 65.75% and 58.58%, respectively. These mutants exhibited maximum activity under the same conditions as wild-type CpBgl (65 ℃ and pH 5.0), slightly improved stabilities compared that of the wild-type, and remarkably enhanced activities in the presence of Mn²⁺ or Fe²⁺. The V_max of CpBgl-Q20C and CpBgl-A240S was increased to 138.18 and 125.14 μmol/mg/min, respectively, from 81.34 μmol/mg/min of the wild-type, and the catalysis efficiency (k_cat/K_m) of CpBgl-Q20C (335.79 min^-1/mM) and CpBgl-A240S (281.51 min^-1/mM) was significantly improved compared with that of the wild-type (149.12 min^-1/mM). When the mutant CpBgl-Q20C were used in the practical degradation of different biomasses, the glucose yields of filter paper, corncob residue, and fungi mycelia residue were increased by 17.68%, 25.10%, and 20.37%, respectively. The spatial locations of the mutation residues in the architecture of CpBgl and their unique roles in the enzyme-substrate binding and catalytic efficiency were probed in this work. These results laid a foundation for evolution of other glycoside hydrolases and the industrial bio-degradation of cellulosic biomass in nature.

Local metabolic response of Escherichia coli to the module genetic perturbations in l-methionine biosynthetic pathway

l-Methionine biosynthesis is through multilevel regulated and multibranched biosynthetic pathway (MRMBP). Because of the complex regulatory mechanism and the imbalanced metabolic flux between branched pathways, microbial production of l-methionine has not been commercialized. In this study, local metabolic response in MRMBP of l-methionine was investigated and various crucial genes in branched pathways were determined. In l-serine pathway, the crucial gene was serABC. In O-succinyl homoserine (OSH) pathway, which was the C4 backbone of l-methionine, metB and metL controlled the metabolic flux jointly. In l-cysteine pathway, the crucial gene cysE^fbr could disturb the flux distribution of local network in l-methionine biosynthesis. However, no crucial gene for l-methionine production in 5-methyl tetrahydrofolate (CH₃-THF) pathway was found. The relation between these pathways was also researched. l-Serine pathway, as the upstream pathway of l-cysteine and CH₃-THF, played a crucial role in l-methionine biosynthesis. l-Cysteine pathway showed the strongest controlling force of the metabolic flux, and OSH pathway was second to l-cysteine pathway. In contrast, CH₃-THF pathway was the weakest, which was probably the mainly limited steps at present and had great potential in further research. In addition, constructed W3110 IJAHFEBC/pA∗HAmL was able to produce 2.62 g/L l-methionine in flask. This study is instructive for l-methionine biosynthesis and provides a new research method of biosynthesizing other metabolic products in MRMBPs.

Evidence for the Cusp Effect in η' Decays into ηπ^{0}π^{0}

Using a sample of 4.3×10^{5} η^{'}→ηπ^{0}π^{0} events selected from the ten billion J/ψ event dataset collected with the BESIII detector, we study the decay η^{'}→ηπ^{0}π^{0} within the framework of nonrelativistic effective field theory. Evidence for a structure at π^{+}π^{-} mass threshold is observed in the invariant mass spectrum of π^{0}π^{0} with a statistical significance of around 3.5σ, which is consistent with the cusp effect as predicted by the nonrelativistic effective field theory. After introducing the amplitude for describing the cusp effect, the ππ scattering length combination a_{0}-a_{2} is determined to be 0.226±0.060_{stat}±0.013_{syst}, which is in good agreement with theoretical calculation of 0.2644±0.0051.