Backbone-enabled modification of peptides with benzoquinone via palladium-catalyzed δ-C(sp2)-H functionalization.

Backbone-enabled site-selective modification of peptides with benzoquinone via Pd-catalyzed δ-C(sp2)-H functionalization has been achieved. The amide groups of peptides serve as internal directional groups, facilitating C-H functionalization through a kinetically less favored six-membered palladacycle. This methodology presents novel opportunities for the late-stage site-selective diversification of peptides.

Near-Infrared Fluorescent Probe for the In Situ Visualization of Oxidative Stress in the Brains of Neuroinflammatory and Schizophrenic Mice.

Schizophrenia is a common mental disorder with unclear mechanisms. Oxidative stress and neuroinflammation play important roles in the pathological process of schizophrenia. Superoxide anion (O2•-) is an important oxidative stress biomarker in vivo. However, due to the existence of the blood-brain barrier (BBB), few near-infrared (NIR) fluorescent probes have been used for the sensing and detection of O2•- in the brain. With this research, we developed the first near-infrared fluorescent probe (named CT-CF3) for noninvasive detection of endogenous O2•- in the brain of mice. Enabling fluorescence monitoring of the dynamic changes in O2•- flux due to the prolonged activation of microglia in neuroinflamed and schizophrenic (SZ) mice brains, thereby providing direct evidence for the relationship between oxidative stress, neuroinflammation, and schizophrenia. Furthermore, we confirmed the O2•- burst in the brains of first-episode schizophrenic mice and assessed the effect of two atypical antipsychotic drugs (risperidone and olanzapine) on redox homeostasis.

Near-Infrared Bodipy-Based Molecular Rotors for ß-Amyloid Imaging In Vivo.

ß-amyloid (Aß) is one of the important biomarkers for diagnosing Alzheimer's disease (AD). Many near-infrared probes based on the donor-π-acceptor structure have been developed to detect Aß. Most reported Aß probes are based on the N,N-dimethylamino group as the ideal donor, which is a widely accepted binding unit. As such, the development of fluorescent probes with improved binding units to detect Aß is urgently required. Therefore, with this research three anchoring molecular rotor electron donors consisting of cyclic amines of different ring sizes are developed, namely five-membered ring (TPyr), six-membered ring (TPip), and seven-membered ring (THAI). These new anchored molecular rotors are connected to a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) and named TPyrBDP, TPipBDP, and THAIBDP. These probes exhibit high affinities (from 28 to 54 nm) for Aß1-42 aggregates. The six-membered ring dye TPipBDP exhibits the highest signal-to-noise (75.5-fold) and higher affinity (28.30 ± 5.94 nm). TPipBDP can cross the blood-brain barrier and exhibits higher fluorescence enhancement with APP/PS1 (AD) double transgenic (Tg) mice than with wild-type (WT) mice.

Site-Selective Modification of Peptides via Late-Stage Pd-Catalyzed Tandem Reaction of Phenylalanine with Benzoquinone.

An efficient and straightforward approach for site-selective functionalization of phenylalanine and phenylalanine-containing peptide via a Pd-catalyzed tandem reaction has been developed. The robust method underwent dual C-H activation, including C-C coupling with benzoquinone and intramolecular C-N cyclization, providing a feasible and rapid synthetic route to incorporate 4-benzoquinone-indoline fragments into peptides.

Recent progress in the development of fluorescent probes for imaging pathological oxidative stress.

Oxidative stress is closely related to the physiopathology of numerous diseases. Reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS) are direct participants and important biomarkers of oxidative stress. A comprehensive understanding of their changes can help us evaluate disease pathogenesis and progression and facilitate early diagnosis and drug development. In recent years, fluorescent probes have been developed for real-time monitoring of ROS, RNS and RSS levels in vitro and in vivo. In this review, conventional design strategies of fluorescent probes for ROS, RNS, and RSS detection are discussed from three aspects: fluorophores, linkers, and recognition groups. We introduce representative fluorescent probes for ROS, RNS, and RSS detection in cells, physiological/pathological processes (e.g., Inflammation, Drug Induced Organ Injury and Ischemia/Reperfusion Injury etc.), and specific diseases (e.g., neurodegenerative diseases, epilepsy, depression, diabetes and cancer, etc.). We then highlight the achievements, current challenges, and prospects for fluorescent probes in the pathophysiology of oxidative stress-related diseases.

Generalized image outpainting with U-transformer.

In this paper, we develop a novel transformer-based generative adversarial neural network called U-Transformer for generalized image outpainting problems. Different from most present image outpainting methods conducting horizontal extrapolation, our generalized image outpainting could extrapolate visual context all-side around a given image with plausible structure and details even for complicated scenery, building, and art images. Specifically, we design a generator as an encoder-to-decoder structure embedded with the popular Swin Transformer blocks. As such, our novel neural network can better cope with image long-range dependencies which are crucially important for generalized image outpainting. We propose additionally a U-shaped structure and multi-view Temporal Spatial Predictor (TSP) module to reinforce image self-reconstruction as well as unknown-part prediction smoothly and realistically. By adjusting the predicting step in the TSP module in the testing stage, we can generate arbitrary outpainting size given the input sub-image. We experimentally demonstrate that our proposed method could produce visually appealing results for generalized image outpainting against the state-of-the-art image outpainting approaches.

Observation of carrier transfer in a vertical 0D-CsPbBr3/2D-MoS2 mixed-dimensional van der Waals heterojunction.

Two-dimensional transition metal dichalcogenides with outstanding properties open up a new way to develop optoelectronic devices such as phototransistors and light-emitting diodes. Heterostructure with light-harvesting materials can produce many photogenerated carriers via charge and/or energy transfer. In this paper, the ultrafast dynamics of charge transfer in zero-dimensional CsPbBr3 quantum dot/two-dimensional MoS2 van der Waals heterostructures are investigated through femtosecond time-resolved transient absorption spectroscopy. Hole and electron transfers in the ps and fs magnitude at the interfaces between MoS2 and CsPbBr3 are observed by modulating pump wavelengths of the pump-probe configurations. Our study highlights the opportunities for realizing the exciton devices based on quantum dot/two-dimensional semiconductor heterostructures.

Fluorescent molecular probes for imaging and detection of oxidases and peroxidases in biological samples.

Oxidases and peroxidases are two subclasses of oxidoreductases. The abnormal expression of oxidases (such as tyrosinase, cytochrome P450 oxidases, and monoamine oxidases) and peroxidases (such as glutathione peroxidase, myeloperoxidase, and eosinophil peroxidase) is relative with some diseases. Therefore, the analysis of oxidases and peroxidases is great important for disease diagnosis and treatment. Fluorescent probes present simple protocol, high sensitivity and good stability in sensing field. Molecule fluorescent probes are constructed with chemical groups that tunes their fluorescence emission in response to binding events, chemical reactions, and the surrounding environment. A fluorescent probe is an efficient tool for visualizing the activity of enzymes in living organisms on the basis of its high specificity, sensitivity, and noninvasiveness characteristics. In this review, we focus on the sensing of oxidases and peroxidases by molecule fluorescent probes, and hope to bring new insight to wide researchers about oxidases and peroxidases in biological samples.

Si-rhodamine fluorescent probe for monitoring of hypochlorous acid in the brains of mice afflicted with neuroinflammation.

Neuroinflammation leads to a persistent oxidative stress in the brain, and is closely related to the pathology of various neurological disorders. Hypochlorous acid (HClO) is a reactive oxygen species (ROS) that, at high levels, can cause brain tissue damage and neurogenic apoptosis. Herein, we designed and synthesized a silicon-rhodamine (SiR)-based formohydrazide (FH)-containing fluorescent probe, denoted as SiR-FH, for sensing HClO. This probe showed good selectivity, rapid response and high sensitivity. SiR-FH was successfully used to detect endogenous and exogenous HClO in living cells. Moreover, SiR-FH realized real-time monitoring of change in HClO flux in the brains of mice with LPS-induced neuroinflammation. The probe provides a practical tool for the monitoring of oxidative stress related to neuroinflammation.

Two Radical SAM Enzymes Are Necessary and Sufficient for the In Vitro Production of the Oxetane Nucleoside Antiviral Agent Albucidin.

Oxetanocin A and albucidin are two oxetane natural products. While the biosynthesis of oxetanocin A has been described, less is known about albucidin. In this work, the albucidin biosynthetic gene cluster is identified in Streptomyces. Heterologous expression in a nonproducing strain demonstrates that the genes alsA and alsB are necessary and sufficient for albucidin biosynthesis confirming a previous study (Myronovskyi et al. Microorganisms 2020, 8, 237). A two-step construction of albucidin 4'-phosphate from 2'-deoxyadenosine monophosphate (2'-dAMP) is shown to be catalyzed in vitro by the cobalamin dependent radical S-adenosyl-l-methionine (SAM) enzyme AlsB, which catalyzes a ring contraction, and the radical SAM enzyme AlsA, which catalyzes elimination of a one-carbon fragment. Isotope labelling studies show that AlsB catalysis begins with stereospecific H-atom transfer of the C2'-pro-R hydrogen from 2'-dAMP to 5'-deoxyadenosine, and that the eliminated one-carbon fragment originates from C3' of 2'-dAMP.

Meta-analysis of the prevalence of anxiety and depression among frontline healthcare workers during the COVID-19 pandemic.

Objective: To systematically review the prevalence of anxiety and depression among frontline healthcare workers during the coronavirus disease 2019 (COVID-19) pandemic. Methods: Computers were used to search CNKI, VIP, WanFang Data, PubMed, and other Chinese and English databases. The search period was limited to December 2019 to April 2022. Cross-sectional studies collected data on the prevalence of anxiety and depression among frontline healthcare workers since the onset of COVID-19. The STATA 15.1 software was used for the meta-analysis of the included literature. Results: A total of 30 studies were included, with a sample size of 18,382 people. The meta-analysis results showed that during the COVID-19 pandemic, the total prevalence of anxiety among frontline healthcare workers was 43.00%, with a 95% confidence interval (CI) of 0.36-0.50, and the total prevalence of depression was 45.00%, with a 95% CI of 0.37-0.52. The results of the subgroup analysis showed that prevalence of anxiety and depression in women, married individuals, those with children, and nurses was relatively high. Frontline healthcare workers with a bachelor's degree or lower had a higher prevalence of anxiety. The prevalence of depression was higher among frontline healthcare workers with intermediate or higher professional titles. Conclusion: During the COVID-19 pandemic, the prevalence of anxiety and depression among frontline healthcare workers was high. In the context of public health emergencies, the mental health status of frontline healthcare workers should be given full attention, screening should be actively carried out, and targeted measures should be taken to reduce the risk of COVID-19 infection among frontline healthcare workers. Systematic review registration: http://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022344706.

Identification of the Early Steps in Herbicidin Biosynthesis Reveals an Atypical Mechanism of C-Glycosylation.

Herbicidins are adenosine-derived nucleoside antibiotics with an unusual tricyclic core structure. Deletion of the genes responsible for formation of the tricyclic skeleton in Streptomyces sp. L-9-10 reveals the in vivo importance of Her4, Her5, and Her6 in the early stages of herbicidin biosynthesis. In vitro characterization of Her4 and Her5 demonstrates their involvement in an initial, two-stage C-C coupling reaction that results in net C5'-glycosylation of ADP/ATP by UDP/TDP-glucuronic acid. Biochemical analyses and intermediate trapping experiments imply a noncanonical mechanism of C-glycosylation reminiscent of NAD-dependent S-adenosylhomocysteine (SAH)-hydrolase catalysis. Structural characterization of the isolated metabolites suggests possible reactions catalyzed by Her6 and Her7. An overall herbicidin biosynthetic pathway is proposed based on these observations.

Si-Rhodamine Derivatives for Brain Fluorescence Imaging and Monitoring of H2S in the Brain of Schizophrenic Mice before and after Treatment.

Schizophrenia is a common type of serious mental illness with an unclear etiology. Recently, the excessive production of hydrogen sulfide in the brain has been considered to be one of the pathophysiological bases of schizophrenia. However, due to the existence of the blood-brain barrier (BBB), almost no fluorescent probe has been successfully used for the sensing and detection of H2S in the brain. Herein, we designed and synthesized a series of near-infrared fluorescent probes SiR-Bs based on a hemicyanine and Si-rhodamine structure. Among them, Mindo-SiR presented a good penetration ability of the BBB, a high brain uptake (transport: 4.95% ID/g at 5 min), and good response to H2S in vitro and in vivo. For the first time, a fluorescent probe was used to image the changes of H2S in the brains of schizophrenic (SZ) mouse models, and it was successfully proven that there was an abnormally high level of H2S in the brains of SZ mice. Moreover, the therapeutic effect of risperidone for the treatment of SZ could be evaluated by the changes of SiR-Bs' fluorescence imaging.

Mitochondria-Targeted Sensor Array with Aggregation-Induced Emission Luminogens for Identification of Various Cells.

Accurate discrimination of cancerous cells is a good solution for early diagnosis of tumors. The mitochondrion plays an important role in cells. Herein, the five aggregation-induced emission luminogens (AIEgens) with various double positive charges are synthesized to image mitochondria. Tetraphenylethylene (TPE) molecules are modified by methoxy groups, conjugated donor-acceptor, and different positive charges to achieve multicolor emission. The five AIEgens form the PTx-Sa (positive mitochondria-target molecular sensor array) to perform cross-fluorescence response based on the mitochondria-targeted imaging to achieve the discrimination of various cells. Principal component analysis of the cross-response fluorescence data of PTx-Sa shows that 100% accurate identification of various cells, including cancer cells and normal cells, digestive tract cancer cells, gastric cancer cells, and mixed gastric cancer cells. By support vector machine to show the predictive ability of PTx-Sa to unknown cells by using blind samples. This is the first time to apply mitochondria-targeted sensor array to identification of various cells.

Identification of the C-Glycoside Synthases during Biosynthesis of the Pyrazole-C-Nucleosides Formycin and Pyrazofurin.

C-Nucleosides are characterized by a C-C rather than a C-N linkage between the heterocyclic base and the ribofuranose ring. While the biosynthesis of pseudouridine-C-nucleosides has been studied, less is known about the pyrazole-C-nucleosides such as the formycins and pyrazofurin. Herein, genome screening of Streptomyces candidus NRRL 3601 led to the discovery of the pyrazofurin biosynthetic gene cluster pyf. In vitro characterization of gene product PyfQ demonstrated that it is able to catalyze formation of the C-glycoside carboxyhydroxypyrazole ribonucleotide (CHPR) from 4-hydroxy-1H-pyrazole-3,5-dicarboxylic acid and phosphoribosyl pyrophosphate (PRPP). Similarly, ForT, the PyfQ homologue in the formycin pathway, can catalyze the coupling of 4-amino-1H-pyrazole-3,5-dicarboxylic acid and PRPP to form carboxyaminopyrazole ribonucleotide. Finally, PyfP and PyfT are shown to catalyze amidation of CHPR to pyrazofurin 5'-phosphate thereby establishing the latter stages of both pyrazofurin and formycin biosynthesis.

The Amipurimycin and Miharamycin Biosynthetic Gene Clusters: Unraveling the Origins of 2-Aminopurinyl Peptidyl Nucleoside Antibiotics.

Peptidyl nucleoside antibiotics (PNAs) are a diverse class of natural products with promising biomedical activities. These compounds have tripartite structures composed of a core saccharide, a nucleobase, and one or more amino acids. In particular, amipurimycin and the miharamycins are novel 2-aminopurinyl PNAs with complex nine-carbon core saccharides and include the unusual amino acids (-)-cispentacin and N5-hydroxyarginine, respectively. Despite their interesting structures and properties, these PNAs have heretofore eluded biochemical scrutiny. Herein is reported the discovery and initial characterization of the miharamycin gene cluster in Streptomyces miharaensis (mhr) and the amipurimycin gene cluster (amc) in Streptomyces novoguineensis and Streptomyces sp. SN-C1. The gene clusters were identified using a comparative genomics approach, and heterologous expression of the amc cluster as well as gene interruption experiments in the mhr cluster support their role in the biosynthesis of amipurimycin and the miharamycins, respectively. The mhr and amc biosynthetic gene clusters characterized encode enzymes typical of polyketide biosynthesis instead of enzymes commonly associated with PNA biosynthesis, which, along with labeled precursor feeding studies, implies that the core saccharides found in the miharamycins and amipurimycin are partially assembled as polyketides rather than derived solely from carbohydrates. Furthermore, in vitro analysis of Mhr20 and Amc18 established their roles as ATP-grasp ligases involved in the attachment of the pendant amino acids found in these PNAs, and Mhr24 was found to be an unusual hydroxylase involved in the biosynthesis of N5-hydroxyarginine. Finally, analysis of the amc cluster and feeding studies also led to the proposal of a biosynthetic pathway for (-)-cispentacin.

Identification of the Formycin A Biosynthetic Gene Cluster from Streptomyces kaniharaensis Illustrates the Interplay between Biological Pyrazolopyrimidine Formation and de Novo Purine Biosynthesis.

Formycin A is a potent purine nucleoside antibiotic with a C-glycosidic linkage between the ribosyl moiety and the pyrazolopyrimidine base. Herein, a cosmid is identified from the Streptomyces kaniharaensis genome library that contains the for gene cluster responsible for the biosynthesis of formycin. Subsequent gene deletion experiments and in vitro characterization of the forBCH gene products established their catalytic functions in formycin biosynthesis. Results also demonstrated that PurH from de novo purine biosynthesis plays a key role in pyrazolopyrimidine formation during biosynthesis of formycin A. The participation of PurH in both pathways represents a good example of how primary and secondary metabolism are interlinked.

Elucidation of the Herbicidin Tailoring Pathway Offers Insights into Its Structural Diversity.

The biosynthetic gene clusters for herbicidins ( hbc) and aureonuclemycin ( anm) were identified in Streptomyces sp. KIB-027 and Streptomyces aureus, respectively. The roles of genes possibly involved in post-core-assembly steps in herbicidin biosynthesis in these clusters and a related her cluster were studied. Through systematic gene deletions, structural elucidation of the accumulated intermediates in the mutants, and in vitro verification of the encoded enzymes, the peripheral modification pathway for herbicidin biosynthesis is now fully established.