Adenine transversion editors enable precise, efficient A•T-to-C•G base editing in mammalian cells and embryos.

Base editors have substantial promise in basic research and as therapeutic agents for the correction of pathogenic mutations. The development of adenine transversion editors has posed a particular challenge. Here we report a class of base editors that enable efficient adenine transversion, including precise A•T-to-C•G editing. We found that a fusion of mouse alkyladenine DNA glycosylase (mAAG) with nickase Cas9 and deaminase TadA-8e catalyzed adenosine transversion in specific sequence contexts. Laboratory evolution of mAAG significantly increased A-to-C/T conversion efficiency up to 73% and expanded the targeting scope. Further engineering yielded adenine-to-cytosine base editors (ACBEs), including a high-accuracy ACBE-Q variant, that precisely install A-to-C transversions with minimal Cas9-independent off-targeting effects. ACBEs mediated high-efficiency installation or correction of five pathogenic mutations in mouse embryos and human cell lines. Founder mice showed 44-56% average A-to-C edits and allelic frequencies of up to 100%. Adenosine transversion editors substantially expand the capabilities and possible applications of base editing technology.

Effect of Abdominal Compression on Total Single-Balloon Enteroscopy Rate: A Randomized Controlled Trial.

OBJECTIVE: To evaluate whether abdominal compression significantly increased the total enteroscopy rate in single-balloon enteroscopy (SBE). METHODS: Consecutive patients who underwent SBE at 2 hospitals were prospectively included between June 1, 2020, and September 30, 2021. They were randomly divided into an abdominal compression group and a non-abdominal compression group with use of sealed envelopes generated by a computer. Total enteroscopy rates were compared between the groups. RESULTS: The study included 200 patients. The total enteroscopy rates were 73% and 16% in the abdominal compression and non-abdominal compression groups, respectively (relative risk, 13.55; 95% CI, 6.79 to 27.00; P<.001). The total enteroscopy rate was higher in the 70 patients who were identified to have undergone no previous abdominal surgery or small intestinal stenosis than in the 32 patients who had undergone such procedures in the abdominal compression group (84% vs 47%; relative risk, 6.08; 95% CI, 2.36 to 15.67; P<.001). Relevant positive findings were not significantly different between the groups (58% vs 45%; P=.07). Binary logistic regression analysis found abdominal compression to be associated with a better total enteroscopy rate (odds ratio, 16.68; 95% CI, 7.92 to 35.15; P<.001), and the presence of previous abdominal surgery or small intestinal stenosis was associated with difficulty in completing the total enteroscopy procedure (odds ratio, 0.26; 95% CI, 0.12 to 0.58; P<.01). CONCLUSION: Abdominal compression significantly increased the total enteroscopy rate in SBE. Complete total enteroscopy may be challenging in patients with a history of abdominal surgery or small intestinal stenosis.

Structural insights into MIC2 recognition by MIC2-associated protein in Toxoplasma gondii.

Microneme protein 2 (MIC2) and MIC2-associated protein (M2AP) play crucial roles in the gliding motility and host cell invasion of Toxoplasma gondii. Complex formation between MIC2 and M2AP is required for maturation and transport from the microneme to the parasite surface. Previous studies showed that M2AP associates with the 6th TSR domain of MIC2 (TSR6), but the detailed interaction remains unclear. In this study, we report crystal structures of M2AP alone and in complex with TSR6. TSR domains have an unusually thin, long structure with a layer of intercalated residues on one side. The non-layered side of TSR6 with hotspot residue His-620 at the center binds to M2AP. Remarkably, we show that TSR6 residue Y602 is dynamic; it equilibrates between being part of the layer (the layered state) and in a flipped-out state in the absence of M2AP. However, when bound to M2AP, Y602 shifts to the flipped-out state. Our findings provide insights into the association and stabilization of MIC2-M2AP complex, and may be used to develop new therapies to prevent infections caused by this parasite.

Molecular insights into the 'defects' network in the thermosets and the influence on the mechanical performance.

The introduction of 'defects' to the thermoset crosslinking network is one of the most applicable strategies for improving the modulus and toughness simultaneously. However, the reinforcement effect disappears when the 'defects' proportion exceeds the threshold. The speculated mechanism was that the aggregation and entanglement of the 'defects' chains changed the matrix topology, making the stacking structure more compact. However, the 'defects' are hardly directly observed in the experiment. As the result, the relationship between the 'defects' proportion and the package state of the matrix, and the effect on the material's mechanical performance was not explored. Herein, the network of bisphenol-A diglycidyl (DGEBA) with diethyltoluenediamine (DETDA) as the hardener was constructed using MD simulation, and n-butylamine was decorated on the matrix by replacing a proportion of DETDA acting as the 'defects'. The results indicated that the aliphatic chains aggregated and entangled at a low concentration, occupying the voids in the rigid aromatic crosslinking structure, thus lowering the free volume. The strong non-bonding interactions drew the matrix segments close together, thus reinforcing the resin. However, the microphases formed by the aliphatic chains no longer filled the voids but created a new free volume and loosened the network when the content increased, which reduced the mechanical performance of the material. The experimental results were consistent with the findings in the simulations. The moduli of the resin increased with the increase in the n-butylamine content first and then declined. The maximum moduli of the thermosets was 3.4 GPa in S30, which was about 25% higher compared with the control; the corresponding elongation at break was 8.9%, which was about 46% improved compared with the control.

Research on Anxiety of Learning Chinese as a Second or Foreign Language in and Outside Mainland China: A Systematic Review of the Literature 1999-2020.

This paper reviews research on anxiety of learning Chinese as a second or foreign language (CSL/CFL) in and outside mainland China. This review involves 52 Chinese language articles identified in leading journals from the Chinese National Knowledge Infrastructure (CNKI) database () and 42 English language articles from the Web of Science and ERIC database published during the period of 1999 to 2020. By adopting bibliometric analysis and content analysis, this study compares the topical issues and methodological approaches of research on CSL/CFL learning anxiety published in leading Chinese and international journals. The review found that, compared with mainland Chinese scholars, international researchers examined a broader range of topical issues from multidimensional perspectives. While most Chinese empirical studies are dominated by the quantitative approach, qualitative methods such as classroom observations and in-depth interviews were also widely adopted by international researchers. The analysis also revealed that although Chinese scholars had drawn on well-established theories and concepts originating from foreign language anxiety (FLA) research, their role in CSL/CFL anxiety research is limited and peripheral. Consequently, we conclude this review with recommendations that encourage mainland Chinese researchers to be well informed by the updated theoretical perspective and methodological approaches such as the utilization of social network analysis and the integration of Information Communications Technology in language education.

Phase-Amplitude Coupling Brain Networks in Children with Attention-Deficit/Hyperactivity Disorder.

In cognitive neuroscience, there is an increasing interest in identifying and understanding the synchronization of distinct neural oscillations with different frequencies that might support dynamic communication within the brain. This study explored the cross-frequency phase-amplitude coupling brain network characteristics of resting-state electroencephalograms between 30 children with attention-deficit/hyperactivity disorder (ADHD) and 30 age-matched typically developing children. Compared with control group, children with ADHD show increased coupling intensity and altered distribution patterns of dominant paired channels, especially in the δ-γH, θ-γH, α-γH, ßL-γH, and ßH-γH coupling networks. Regarding graph theory properties, the characteristic path length, the mean clustering coefficient, the global efficiency, and the mean local efficiency significant difference in many cross-frequency coupling networks, especially in the δ-γH, θ-γH, α-γH, ßL-γH, and ßH-γH coupling networks. The area under the receiver operating characteristic curve (AUC) in low-frequency coupling with a high-gamma frequency was larger than that in coupling with low-gamma frequency (AUC values of δ-γL, θ-γL, α-γL, ßL-γL, ßH-γL, δ-γH, θ-γH, α-γH, ßL-γH, and ßH-γH were 0.794, 0.722, 0.666, 0.570, 0.881, 0.992, 0.998, 0.998, 0.989, and 0.974, respectively). These findings demonstrate altered coupling intensity and disrupted topological organization of coupling networks, support the altered brain network theory in children with ADHD. The coupling intensity and graph theory properties of low-frequency coupling with high-gamma frequency were promising resting-state electroencephalogram biomarkers of ADHD in children.

A Study on Resting EEG Effective Connectivity Difference before and after Neurofeedback for Children with ADHD.

Altered functional networks in attention deficit/hyperactivity disorder (ADHD) have been frequently reported, but effective connectivity has hardly been studied. Especially the differences of effective connectivity in children with ADHD after receiving neurofeedback (NF) training have been merely reported. Therefore, this study aimed to explore the effective networks of ADHD and the positive influence of NF on the effective networks. Electroencephalogram (EEG) data were recorded from 22 children with ADHD (including data from children pretraining and posttraining) and 15 age-matched healthy controls during an eyes-closed resting state. Phase transfer entropy (PTE) was used to construct the effective connectivity. The topological properties of networks and flow gain were measured separately in four bands (delta, theta, alpha, and beta). Results revealed the following: pretraining children with ADHD manifested a higher clustering coefficient and lower characteristic path length in the delta band than healthy controls; weakened anterior-to-posterior flow gain in the delta band, strengthened posterior-to-anterior flow gain in the alpha band and strengthened anterior-to-posterior flow gain in the beta band were observed in pretraining children with ADHD; The topological properties and flow gain in posttraining children with ADHD were close to those of healthy controls. Moreover, parent's SWAN presented significant improvements of ADHD symptoms after NF. Our findings revealed that the effective connectivity of ADHD was altered and that NF could improve the brain function of ADHD. The present study provided the first evidence that children with ADHD differed from healthy children in phase-based effective connectivity and that NF could reduce the differences.

Mapping abandoned farmland in China using time series MODIS NDVI.

Farmland abandonment is an important aspect of land cover land use (LCLU) that has both positive and negative effects on the environment. There is limited information regarding the spatial distribution of abandoned farmland in China. In this study, we 1) use a C5.0 decision tree classification based on a 250 m spatial resolution Moderate-resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) time series to develop LCLU maps for the period 2000-2017; 2) produce time series maps of the abandoned farmland during the period 2002-2017 based on LCLU maps; and 3) analyze spatial distribution, intensity, trend, frequency, and recultivation in terms of farmland abandonment. The results show that the overall accuracy of the LCLU maps ranged from 85.45% to 90.56% over the study period (2002-2017). The average national rate of farmland abandonment was 5% over the period 2002-2017, with the lowest rate in 2002 and the highest in 2015. Approximately 60% of the 34 agricultural areas in China showed an increasing trend for abandonment including some of the main grain-producing areas such as the North China Plain and the middle and lower reaches of the Yangtze River. Abandoned farmland areas with an abandonment frequency of ≤ 3 y comprised 58.24% of the total area of abandoned farmland. The first map detailing the distribution of the abandoned farmland across China was produced in this study, providing guidance for the development of a method of identifying abandoned farmland on a large spatial scale.

Characteristics of water absorption in amine-cured epoxy networks: a molecular simulation and experimental study.

Moisture corrosion of cured epoxy resins seriously affects the durability of epoxy products and has been a serious issue in scientific and engineering fields. In this study, a series of cured epoxy resins with different structures were prepared by tuning their curing conversion in both experimental and simulation methods. In experiments, the equilibrium water content and the diffusion coefficient of amine-cured epoxy resins were measured by gravimetric measurement. The interaction between water molecules and epoxy network was investigated by time-resolved FTIR, difference spectroscopy and 2D correlation spectroscopy. In simulation, the hydrogen bonds, the mobility of hydroxypropyl ether groups and water molecules, and the free volume with its distributions were analyzed. Five types of water molecules were intuitively observed in this study; free volume had a stronger influence on equilibrium water content than polarity in the bifunctional epoxy/amine system, and the increase in the diffusion coefficient was considered as the result of reduction in motion resistance and an increase in channels for the motion of water molecules.

Medicinal chemistry of small molecule CCR5 antagonists for blocking HIV-1 entry: a review of structural evolution.

CCR5, a member of G protein-coupled receptors superfamily, plays an important role in the HIV-1 entry process. Antagonism of this receptor finally leads to the inhibition of R5 strains of HIV entry into the human cells. The identification of CCR5 antagonists as antiviral agents will provide more option for HAART. Now, more than a decade after the first small molecule CCR5 inhibitor was discovered, great achievements have been made. In this article, we will give a brief introduction of several series of small molecule CCR5 antagonists, focused on their appealing structure evolution, essential SAR information and thereof the enlightenment of strategies on CCR5 inhibitors design.

Simultaneous determination of lercanidipine, benazepril and benazeprilat in plasma by LC-MS/MS and its application to a toxicokinetics study.

We aim to develop a rapid, simple, sensitive and specific LC-MS/MS method for the simultaneous quantification of lercanidipine, benazepril and benazeprilat in plasma. It is performed on the Agilent 6410 LC-MS/MS under the multiple-reaction monitoring (MRM) mode with electrospray ionization. Gliclazide was used as the internal standard (IS). Analytes and IS were extracted from plasma by solid-phase extraction. The reconstituted samples were chromatographed on a Diamond C18(150 mm × 4.6 mm, 5 µm) column. The mobile phase was composed of 0.1% acetic acid-acetonitrile (50:50, v/v), with gradient flow rates: 0.6 mL/min (0-4.55 min); 4.55-4.65 min, 1 mL/min; 1 mL/min (4.65-9.5 min); 9.5-9.6 min, 0.6 mL/min; 0.6 mL/min (9.6-10 min). Method validation demonstrated that the method was of satisfactory specificity, sensitivity, precision and accuracy in linear ranges of 1-2000 ng/mL for lercanidipine, 1-2000 ng/mL for benazepril and 1-1600 ng/mL for benazeprilat, respectively. The precision (RSD%) was better than 15, and the lower limit of quantitation was identifiable and reproducible at 1 ng/mL for the three analytes. The plasma samples were stable after being stored for more than 60 days and after two freeze-thaw cycles (-20 to -25 °C). It is demonstrated that this method was successfully applied to samples from a toxicokinetics study of a compound of lercanidipine and benazepril in beagle dogs.

Determination of salbutamol in human plasma and urine using liquid chromatography coupled to tandem mass spectrometry and its pharmacokinetic study.

A sensitive and selective liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed and validated for the determination of salbutamol in human plasma and urine, and successfully applied to the pharmacokinetic study of salbutamol in Chinese healthy volunteers after inhalation of salbutamol sulfate aerosol. Salbutamol and the internal standard (IS) acetaminophen in plasma and urine were extracted with ethyl acetate, separated on a C(18) reversed-phase column, eluted with mobile phase of acetonitrile-ammonium acetate (5 m m; 30:70, v/v), ionized by positive ion pneumatically assisted electrospray and detected in the multi-reaction monitoring mode using precursor → product ions of m/z 240.2 → 148.1 for salbutamol and 152 → 110 for the IS. The lower limits of quantitation of salbutamol in human plasma and urine by this method were 0.02 and 1 ng/mL, respectively. The specificity, matrix effect, recovery, sensitivity, linearity, accuracy, precision and several stabilities were validated for salbutamol in human plasma and urine. In conclusion, the validation results showed that this method is robust, specific and sensitive, and can successfully fulfill the requirement of clinical pharmacokinetic study of salbutamol in healthy Chinese volunteers.

Poly(para-dioxanone)/inorganic particle composites as a novel biomaterial.

In this work, poly(para-dioxanone) (PPDO) was mixed with 1% (by weight) calcium carbonate (CaCO(3)), beta-tricalcium phosphate (beta-TCP), or calcium sulphate dihydrate (CSD) by solution co-precipitation. Samples were compression molded into bars using a platen-vulcanizing press. The morphology, thermal and mechanical properties, and crystalline structure of the composites were investigated using differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X-ray diffraction. All results suggest that three types of inorganic particle in this system promote the crystallinity of PPDO and act as an effective nucleating agent: the relative degree of crystallinity of PPDO increased from 30.74% to 100%, and the crystallization temperature of PPDO was increased by 18 degrees C. On the other hand, the mechanical properties of PPDO were changed by the presence of inorganic particles: the tensile strength of PPDO/CSD increased by 11.46%.