Catalytic Asymmetric Synthesis of Chiral α,α-Dialkyl Aminonitriles via Reaction of Cyanoketimines.

Chiral aminonitriles not only are broadly useful building blocks but also increasingly appear as structural motifs in bioactive molecules and pharmaceuticals. The catalytic asymmetric synthesis of chiral aminonitriles, therefore, has been intensively investigated, as reflected in numerous reports of catalytic asymmetric Strecker reactions. Despite such great progress, the catalytic asymmetric synthesis of chiral α,α-dialkyl aminonitriles in a highly selective and efficient manner is still a formidable challenge. Here, we report a new approach for the catalytic asymmetric synthesis of chiral α,α-dialkyl aminonitriles via reaction of cyanoketimines with enals. We demonstrate that this reaction could be carried out with as low as 20 ppm catalyst loading.

Catalytic Asymmetric Construction of Chiral Amines with Three Nonadjacent Stereocenters via Trifunctional Catalysis.

Pharmaceuticals and biologically active natural products usually contain multiple stereocenters. The development of catalytic asymmetric reactions for the direct construction of complex motifs containing three nonadjacent stereocenters is a particularly important and formidable challenge. In this paper, we report an unprecedented method for the direct asymmetric construction of complex chiral amines with 1,3,5- or 1,3,4-stereocenters from readily available achiral and racemic starting materials. The reaction was made possible by the development of highly efficient chiral ammonium catalysts that serve three distinct functions: promoting efficient kinetic resolution by chiral recognition of racemic electrophiles, promoting asymmetric C-C bond forming reactions by recognizing enantiotropic faces of achiral nucleophiles, and mediating a highly stereoselective protonation of carbanions. Using these trifunctional catalysts, the reaction of imines and tulipane derivatives proceeded in a highly regio-, chemo-, and stereoselective manner to produce synthetically useful yields of complex chiral amines. We believe that trifunctional catalysis can be applied in a variety of asymmetric transformations for the streamlined asymmetric synthesis of complex chiral molecules with multiple stereocenters.

Synthesis of α-Aminonitriles via Ammonium-Catalyzed Reactions of Aminoacetonitrile.

α-Aminonitriles are not only broadly useful building blocks but also structural motifs in bioactive molecules. The Strecker reaction is one of the most widely used methods for α-aminonitrile synthesis. However, a severe drawback in Strecker reactions is the required use of a stoichiometric amount of toxic cyanation reagents. Thus, the development of a greener and widely applicable method for the synthesis of aminonitriles from readily available starting materials presents an important yet unmet challenge. We developed a general and new method for the synthesis of aminonitriles from readily available aminoacetonitrile. This method utilized off-the-shelf ammonium salts as catalysts, tolerated air and moisture, and avoided the use of cyanation reagents, which rendered it a greener alternative to the widely practiced Strecker reaction approach. We further illustrated that chiral ammonium-catalyzed asymmetric reactions of N-arylidene aminoacetonitriles could provide chiral α-tertiary and α-quaternary aminonitriles and α-aminonitriles bearing two continuous stereocenters.

Lima bean (Phaseolus lunatus Linn.) protein isolate as a promising plant protein mixed with xanthan gum for stabilizing oil-in-water emulsions.

BACKGROUND: Lima bean protein isolate (LPI) is an underutilized plant protein. Similar to other plant proteins, it may display poor emulsification properties. In order to improve its emulsifying properties, one effective approach is using protein and polysaccharide mixtures. This work investigated the structural and emulsifying properties of LPI as well as the development of an LPI/xanthan gum (XG)-stabilized oil-in-water emulsion. RESULTS: The highest protein solubility (84.14%) of LPI was observed and the molecular weights (Mw ) of most LPI subunits were less than 35 kDa. The enhanced emulsifying activity index (15.97 m2 g-1 ) of LPI might be associated with its relatively high protein solubility and more low-Mw subunits (Mw < 35 kDa). The effects of oil volume fraction (ϕ) on droplet size, microstructure, rheological behavior and stability of emulsions were investigated. As ϕ increased from 0.2 to 0.8, the emulsion was arranged from spherical and dispersed oil droplets to polyhedral packing of oil droplets adjacent to each other, while the LPI/XG mixtures changed from particles (in the uncrowded interfacial layer) to lamellae (in the crowded interfacial layer). When ϕ was 0.6, the emulsion was in a transitional state with the coexistence of particles and lamellar structures on the oil droplet surface. The LPI/XG-stabilized emulsions with ϕ values of 0.6-0.8 showed the highest stability during a 14-day storage period. CONCLUSION: This study developed a promising plant-based protein resource, LPI, and demonstrates potential application of LPI/XG as an emulsifying stabilizer in foods. © 2023 Society of Chemical Industry.

Revealing the Orientation Selectivity of Tetrapyridyl-Substituted Porphyrins Constrained in Molecular "Klotski Puzzles".

Understanding and controlling molecular orientations in self-assembled organic nanostructures are crucial to the development of advanced functional nanodevices. Scanning tunneling microscopy (STM) provides a powerful toolbox to recognize molecular orientations and to induce orientation changes on surfaces at the single-molecule level. Enormous effort has been devoted to directly controlling the molecular orientations of isolated single molecules in free space. However, revealing and further controlling molecular orientation selectivity in constrained environments remain elusive. In this study, by a combination of STM imaging/manipulations and density functional theory calculations, we report the orientation selectivity of tetrapyridyl-substituted porphyrins in response to various local molecular environments in artificially constructed molecular "Klotski puzzles" on Au(111). With the assistance of STM lateral manipulations, "sliding-block" molecules were able to enter predefined positions, and specific molecular orientations were adopted to fit the local molecular environments, in which the intermolecular interaction was revealed to be the key to achieving the eventual molecular orientation selectivity. Our results demonstrate the essential role of local molecular environments in directing single-molecule orientations, which would shed light on the design of molecular structures to control preferred orientations for further applications in molecular nanodevices.

Treatment of Polycystic Ovary Syndrome-Related Infertility Using a Combination of Compound Xuanju Capsules and Hormones: A Meta-Analysis.

Objective: Our aim was to perform a meta-analysis to compare the therapeutic effects of compound Xuanju capsules combined with hormone therapy vs hormone therapy alone in polycystic ovary syndrome (PCOS)-related infertility. Methods: Electronic databases including PubMed, The Cochrane Library, Web of Science, Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), Wanfang Data and VIP database were manually searched. The quality of included studies was evaluated based on Cochrane Systematic Review standards, and the valid data were extracted for meta-analysis using RevMan 5.3 software (Cochrane Review). Results: A total of 14 randomized controlled trials (RCTs) including 1249 patients were included in the study. Meta-analysis showed that patients in the compound Xuanju capsule + hormone therapy group had higher estradiol (E2) levels and overall rates of effective treatment than patients in the hormone therapy alone group. Moreover, they exhibited lower levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), as well as lower Kupperman scores, than the hormone therapy alone group. Conclusions: The combination of compound Xuanju capsules and hormone therapy is more effective than hormone therapy alone in the treatment of PCOS-related infertility. However, the quality of current studies is low, and high-quality clinical trials are warranted.

Fungal dynamic changes in naturally fermented 'Kyoho' grape juice.

The 'Kyoho' grape (Vitaceae, Plantae) has large ears, plenty of flesh, and rich nutrition and is planted across a large area in China. There are few reports on this variety in winemaking, especially on the dynamic changes of fungi in the wine fermentation broth. In this study, we used the 'Kyoho' grapes as raw materials and adopted a high throughput to analyze dynamic changes in fungal species composition of the natural fermentation broth at four time points: day 1 (D1P), day 3 (D3P), day 5 (D5P), and day 15 (D15P). Changes in fungal metabolic pathways and dominant yeasts were also analyzed. A total of 78 families, 110 genera, and 137 species were detected, in the natural fermentation broth samples. Forty-nine families, 60 genera, and 72 species were found in the control check (CK). A total of 66 differential metabolic pathways were enriched; of those, 41 were up-regulated compared to CK, such as CDP-diacylglycerol biosynthesis I (PWY 5667), chitin degradation to ethanol (PWY 7118), and the super pathway of phosphatidate biosynthesis (PWY 7411). Changes in fungal metabolic pathways were in line with the dynamic changes of dominant yeast species in the whole process of fermentation. Pichia kluyveri, P. membranifaciens, and Citeromyces matritensis are the dominant species in the later stages of natural fermentation. These yeast species may play vital roles in the 'Kyoho' wine industry in the future.

Baoshanmycin and a New Furanone Derivative from a Soil-Derived Actinomycete, Amycolatopsis sp. YNNP 00208.

Actinomycetes have being regarded as a treasure reservoir of various bioactive secondary metabolites and devoted many antibiotics in clinicals. Amycolatopsis sp. YNNP 00208 was isolated from a soil sample collected in Gaoligong Mountain area, Yunnan Province, China. Chemical investigation of its fermentation broth led to a new amide, baoshanmycin (1), and a new furanone derivative, 3-(1,3-dihydroxybutyl)-4-methylfuran-2(H)-one (2), together with eight known compounds, including two amides (3-4), four cyclic dipeptides (5-8), and two deoxyribonucleosides (9-10). Their structures were established on basis of the 1D- and 2D-NMR spectroscopic data, along with the HR-ESI-MS experiments. Baoshanmycin (1) showed moderate antimicrobial activities against Candida albicans, and weak activities against Staphylococcus aureus, multi-drug resistant Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, fluconazole-resistant Candida albicans. Baoshanmycin (1) presented strong antioxidant activity and moderate anti-acetylcholinesterase activity. The other compound 3-(1,3-dihydroxybutyl)-4-methylfuran-2(H)-one (2) and the known compounds (3-10) showed moderate antioxidant activity.

Three new diphenyl ether derivatives from the fermentation products of an endophytic fungus Phomopsis fukushii.

Three new diphenyl ethers (1-3), together with four known isopentylated diphenyl ethers derivatives (4-7), were isolated from the fermentation products of an endophytic fungus Phomopsis fukushii. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1-3 were evaluated for their anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity. The results revealed that compounds 1 and 2 showed strong inhibitions with inhibition zone diameters (IZD) of 20.2 ± 2.5 mm and 17.9 ± 2.2 mm, respectively. Compound 3 also showed good inhibition with IZD 15.2 ± 1.8 mm. The IZD data of compound 1 is close to that of positive control with IZD 21.9 ± 2.1 mm.

Positivity and incidence of human papillomavirus in women attending gynecological department of a major comprehensive hospital in Kunming, China 2012-2014.

HPV DNA testing is receiving increasing popularity in cervical cancer screening. There is a lack of universal guidelines on HPV testing. Our study aimed to assess age-specific and year-on-year trend of HPV positivity and incidence and HPV retesting among 26,457 individual women attending the gynecological department at the First People's Hospital of Yunnan Province (FPHY) who had an HPV testing between January 1, 2012 and December 31, 2014. HPV 16, HPV 52, and cp8304 ranked among top 5 with regard to positivity in each year and overall incidence. The positivity of various HPV types peaked among women aged 15-19 years, then sharply decreased with age, stabilized among women aged 25-49 years and then surged again among women aged 50 years and older. The positivity of high-risk (HR) HPV types, including HPV 16, 18, 31, 33, 56 and 58, were on the rise during the time period (P < 0.05 for all). HR HPV types tended to be more likely to persist than LR HPV types (P < 0.05). Additionally, the incidence rate for any HR HPV type was also significantly higher than that for any LR HPV type (42.8 vs. 12.6 per 100 person-years, P < 0.001). The majority (57.3-77.5%) of women detected with HR HPV types did not retest within 12 months. Clinical guidelines on HPV DNA testing are needed and education, and counseling about HPV infection and its implications for women detected with HPV at clinical settings, are warranted.

Separation of Halogen Atoms by Sodium from Dehalogenative Reactions on a Au(111) Surface.

On-surface dehalogenative reactions have been promising in the construction of nanostructures with diverse morphologies and intriguing electronic properties, while halogen (X), as the main byproduct, often impedes the formation of extended nanostructures and property characterization, and the reaction usually requires high C-X activation temperatures, especially on relatively inert Au(111). Enormous efforts in precursor design, halogen-to-halide conversion, and the introduction of extrinsic metal atoms have been devoted to either eliminating dissociated halogens or reducing reaction barriers. However, it is still challenging to separate halogens from molecular systems while facilitating C-X activation under mild conditions. Herein, a versatile halogen separation strategy has been developed based on the introduction of extrinsic sodium (Na) into dehalogenative reactions on Au(111) as model systems that both isolates the dissociated halogens and facilitates the C-Br activation under mild conditions. Moreover, the combination of scanning tunneling microscopy imaging and density functional theory calculations reveals the formation of sodium halides (NaX) from halogens in these separation processes as well as the reduction in reaction temperatures and barriers, demonstrating the versatility of extrinsic sodium as an effective "cleaner" and "dehalogenator" of surface halogens. Our study demonstrates a valuable strategy to facilitate the on-surface dehalogenative reactions, which will assist in the precise fabrication of low-dimensional carbon nanostructures.

Revealing the Influence of Molecular Chemisorption Direction on the Reaction Selectivity of Dehalogenative Coupling on Au(111): Polymerization versus Cyclization.

The control of reaction selectivity is of great interest in chemistry and depends crucially on the revelation of key influencing factors. Based on well-defined molecule-substrate model systems, various influencing factors have been elucidated, focusing primarily on the molecular precursors and the underlying substrates themselves, while interfacial properties have recently been shown to be essential as well. However, the influence of molecular chemisorption direction on reaction selectivity, as a subtle interplay between molecules and underlying substrates, remains elusive. In this work, by a combination of scanning tunneling microscopy imaging and density functional theory calculations, we report the influence of molecular chemisorption direction on the reaction selectivity of two types of dehalogenative coupling on Au(111), i.e., polymerization and cyclization, at the atomic level. The diffusion step of a reactive dehalogenated intermediate in two different chemisorption directions was theoretically revealed to be the key to determining the corresponding reaction selectivity. Our results highlight the important role of molecular chemisorption directions in regulating the on-surface dehalogenative coupling reaction pathways and products, which provides fundamental insights into the control of reaction selectivity by exploiting some subtle interfacial parameters in on-surface reactions for the fabrication of target low-dimensional carbon nanostructures.

Isolation of triazole-resistant Aspergillus fumigatus harbouring cyp51A mutations from five patients with invasive pulmonary aspergillosis in Yunnan, China.

Invasive aspergillosis (IA) is the most severe type of Aspergillus infection. Yunnan has developed agriculture, and the proportion of triazole-resistant A. fumigatus induced by triazole fungicides is much higher than that in other regions of China. Inhalation of triazole-resistant A. fumigatus is one of the main factors inducing IA. We gathered five strains of A. fumigatus from the sputum or bronchoalveolar lavage fluid (BALF) of patients with IA in Yunnan. Subsequent testing showed that all of these strains were resistant to triazoles and harboured mutations in the tandem repeat sequence of the cyp51A promoter region, suggesting that they may be triazole-resistant A. fumigatus present in the environment.

Post-anthesis dry matter and nitrogen accumulation, partitioning, and translocation in maize under different nitrate-ammonium ratios in Northwestern China.

Introduction: An appropriate supply of ammonium (NH4+) in addition to nitrate (NO3-) can greatly improve plant growth and promote maize productivity. However, knowledge gaps exist regarding the mechanisms by which different nitrogen (N) fertilizer sources affect the enzymatic activity of nitrogen metabolism and non-structural carbohydrates during the post-anthesis period. Methods: A field experiment across 3-year was carried out to explore the effects of four nitrateammonium ratio (NO3-/NH4+ = 1:0 (N1), 1:1 (N2), 1:3 (N3), and 3:1 (N4)) on postanthesis dry matter (DM) and N accumulation, partitioning, transportation, and grain yield in maize. Results: NO3-/NH4+ ratio with 3:1 improved the enzymatic activity of N metabolism and non-structural carbohydrate accumulation, which strongly promoted the transfer of DM and N in vegetative organs to reproductive organs and improved the pre-anthesis DM and nitrogen translocation efficiency. The enzymatic activities of nitrate reductase, nitrite reductase, glutamine synthetase, glutamine oxoglutarate aminotransferase, and non-structural carbohydrate accumulation under N4 treatment were increased by 9.30%-32.82%, 13.19%-37.94%, 4.11%-16.00%, 11.19%-30.82%, and 14.89%-31.71% compared with the other treatments. Mixed NO3--N and NH4+-N increased the total DM accumulation at the anthesis and maturity stages, simultaneously decreasing the DM partitioning of stem, increasing total DM, DM translocation efficiency (DMtE), and contribution of pre-anthesis assimilates to the grain (CAPG) in 2015 and 2017, promoting the transfer of DM from stem to grain. Furthermore, the grain yield increased by 3.31%-9.94% (2015), 68.6%-26.30% (2016), and 8.292%-36.08% (2017) under the N4 treatment compared to the N1, N2, and N3 treatments. Conclusion: The study showed that a NO3-/NH4+ ratio of 3:1 is recommended for high-yield and sustainable maize management strategies in Northwestern China.

Interaction of phosphorus and GA3 improved oilseed flax grain yield and phosphorus-utilization efficiency.

Introduction: Phosphorus nutrition and hormone concentration both affect crop yield formation. Ascertaining the interaction of phosphorus and GA3 has a synergistic effect on the grain yield and phosphorus utilization efficiency of oilseed flax in dryland. It is extremely important for improving grain yield and phosphorus utilization efficiency. Methods: A field experiment was conducted in 2019 and 2020 at the Dingxi Oil Crops Test Station to investigated the effects of phosphorus, gibberellin (GA3), and their interaction on the grain yield and phosphorus-utilization efficiency of oilseed flax plants. Phosphorus fertilizer was applied at three levels (0, 67.5, 135 kg P2O5·ha-1) and GA3 was also sprayed at three concentrations (0, 15, and 30 mg·L-1). Results: The results showed that application of 67.5 kg P2O5·ha-1 reduced leaves acid phosphatase (ACPase) activity, but increased phosphorus accumulation throughout the growth period, the 1000-kernel weight (TKW), and the number of grains per capsule. Spraying GA3 significantly increased the leaves ACPase activity, phosphorus accumulation after anthesis and its contribution to grain, phosphorus-utilization efficiency, the number of capsules per plant, and TKW. The phosphorus accumulation at the anthesis, kernel, and maturity stages under the treatment of fertilizing 67.5 kg P2O5·ha-1 and spraying 30 mg·L-1 GA3 were increased by 56.06%, 73.51%, and 62.17%, respectively, compared with the control (no phosphorus, no GA3). And the phosphorus accumulation after anthesis and its contribution to grain also increased. 67.5 kg P2O5·ha-1 combined with 30 mg·L-1 GA3 and 135 kg P2O5·ha-1 combined with 15 mg·L-1 GA3 both significantly increased grain yield of oilseed flax, reaching 1696 kg·ha-1 and 1716 kg·ha-1 across two years, respectively. And there was no significant difference between them. However, the former treatment significant increased the apparent utilization rate, agronomic utilization rate, and partial productivity of phosphorus. The interaction between phosphorus and GA3 was significant for grain yield. Conclusion: Therefore, the application of 67.5 kg P2O5·ha-1 in combination with 30 mg·L-1 GA3 is an effective fertilization approach for enhancing oilseed flax growth and grain yield in the experiment region and other similar areas.

Effects of herbal formula on growth performance, apparent digestibility, antioxidant capacity, and rumen microbiome in fattening lambs under heat stress.

Heat stress (HS) causes severe economic losses in sheep industry worldwide. The objective of the present study was to investigate the effects of a herbal formula (HF) supplement on growth, digestibility, antioxidant capacity, and rumen microbes in fattening lambs under HS. The HF composed of four herbs was prepared based on the theory of compatibility of Chinese medicine "Jun-Chen-Zuo-Shi". Two-hundred forty 3-month weaned lambs (initial weight 36.61 ± 0.73 kg) were randomly allocated into four groups, supplemented 0% (Control), 0.5%, 1.0%, and 1.5% HF in diets. All lambs were exposed to HS conditions with 79.7 of average temperature-humidity index throughout an experimental period of 35 days. Growth performance, apparent digestibility, and antioxidant activities, involving antioxidant enzymes and heat shock proteins (HSPs), were measured at the end of trial, as well as microbial communities in bacteria and archaea. Results showed that 0.5% HF increased (P = 0.02) average daily gain by 13.80% and decreased feed-to-gain ratio (P = 0.03) by 14.68%, compared to control. With increasing HF doses, the digestibility of ether extract and acid detergent fiber demonstrated a cubical (P < 0.01) and quadratic (P = 0.03) relation, respectively; moreover, glutathione peroxidase and catalase activities demonstrated a quadratic increase (P < 0.01). Serum levels of HSP60, HSP70, and HSP90 for 0.5% HF were lower than that in control (P < 0.05). On the other hand, total volatile fatty acid, acetic acid, butyric acid, valeric acid, and isovaleric acid levels exhibited quadratic increases (P ≤ 0.01) with HF doses. From rumen microbes, the abundance and diversity of bacterial community were improved by HF supplements. Particularly for 0.5% HF group, the operational taxonomic units were the greatest among all groups. Compared to control, Prevotella abundance for HF supplements from 0.5 to 1.5% increased by 35.57 to 60.15%, and Succiniclasticum abundance demonstrated a quadratic pattern (P = 0.02) with doses. Additionally, Methanosphaera abundance in archaeal community raised by 0.2 to 3.3-folds when lambs were fed the HF additions of 0.5 to 1.5%. In summary, dietary HF supplements would contribute to alleviating HS in lambs, and our results suggest the optimal dose of 0.5% HF supplement in diet.

Effect of oxygen free radicals and nitric oxide on apoptosis of immune organ induced by selenium deficiency in chickens.

Selenium is an essential element with antioxidant roles in immune regulation, but there is little understanding of how Se acts in apoptosis in the immune organs of birds. The aim of study was to evaluate the influence of Se deficiency on oxygen free radicals, NO and apoptosis in immune organ of chickens. 160 1-day-old chickens were randomly assigned to two groups of 80 each and were fed on a low-Se diet (0.032 mg/kg Se) or a control diet (0.282 mg/kg Se), respectively. OFR production in blood was determined on days 30, 45, 60 and 75, respectively. The iNOS-NO system activity in immune organ (thymus, spleen, bursa of fabricius) was identified by NO content and NOS activity assay on days 30, 45, 60 and 75, respectively. Apoptosis was measured by DNA ladder analysis, ultrastructural observations, TdT-mediated dUTP nick end labeling TUNEL assay and flow cytometric analysis of apoptotic DNA. The transcription of factor-associated suicide, caspase-3 mRNA was tested by fluorescence quantitative PCR. The results showed that OFR production, NO and inducible NO synthases (iNOS) activity in the low-Se group were significantly increased (p < 0.05) than in the control group. In addition, apoptosis was observed in chicken immune organ in the low-Se group. The degree and the number of apoptotic cells rose in a time-dependent manner. The expression of Fas and caspase-3 mRNA increased (p < 0.05) than in the control group. It indicated that the oxidative stress and NO played a causative role in the apoptosis of immune tissues induced by selenium deficiency.

Gene expression responses in different regions of Eisenia fetida with antiparasitic albendazole exposure.

Albendazole (ABZ) is a veterinary drug with a high efficiency against parasite. The aim of this research is to investigate and characterize the response of gene expression in different regions of earthworms Eisenia fetida in relation to ABZ exposure. In this research, the earthworms were exposed to ABZ at 0, 10, 30, 90, and 270 mg/kg concentrations for 42 days. Within the initial 14-day exposure, the expression levels of two target genes (mitochondrial large ribosomal subunit (l-rRNA) and heat shock protein (HSP90)) in different regions of earthworms were affected significantly by the different exposure concentrations of ABZ, but the growth rates were similar among the ABZ and control groups. With longer exposure time, growth rates decreased significantly after 28 days of exposure at 90 and 270 mg/kg. These results of target genes expression suggest that, at low ABZ concentrations, the middle region of earthworms is more sensitive to ABZ than the anterior and posterior regions. In the middle region, the l-rRNA expression of the ABZ-exposed groups was significantly lower than the control group, with a reduction to 23%, 25% and 31% for 10, 30 and 90 mg/kg ABZ concentrations, respectively (P<0.01). In contrast, the HSP90 expression of the ABZ groups (full range of 10 to 270 mg/kg) in the middle region increased 4.1-8.7 folds over the control group (P<0.01). In the anterior and posterior regions, the expression of the two target genes at 10mg/kg did not differ significantly among the ABZ and control groups (P>0.05), except for l-rRNA in the posterior region. The characterization and understanding of target genes expression in different regions of earthworms can provide important information on predictive early reading on the pollution of ABZ residue in soils.

Visualizing the Hierarchical Evolution of Aryl-Metal Bonding in Organometallic Nanostructures on Ag(111).

On-surface dehalogenative coupling reactions are promising for constructing nanostructures with diverse properties and functionalities. Extensive efforts have been devoted to single aryl-halogen (C-X) substituents and substitutions at various functionalization sites (typically including meta- and para-substitutions) to generate aryl-aryl single bonds. Moreover, multiple C-X substituents at the ortho-site and the peri- and bay-regions have been applied to create a variety of ring scaffolds. However, for multiple C-X substituents, the hierarchy of aryl-metal bond formation and dissociation remains elusive. Herein, by combining scanning tunneling microscopy imaging and density functional theory calculations, we have visualized and demonstrated the hierarchical evolution of aryl-metal bonding in organometallic intermediates involved in a dehalogenative coupling reaction on Ag(111), using a molecular precursor with both para-substitution and potential bay-region substitution. Our results elucidate how metal atoms are progressively embedded into and removed from organometallic intermediates, enhancing the understanding of on-surface dehalogenative coupling reactions for the controlled construction of the desired nanostructures.

Bifunctionality of the thiamin diphosphate cofactor: assignment of tautomeric/ionization states of the 4'-aminopyrimidine ring when various intermediates occupy the active sites during the catalysis of yeast pyruvate decarboxylase.

Thiamin diphosphate (ThDP) dependent enzymes perform crucial C-C bond forming and breaking reactions in sugar and amino acid metabolism and in biosynthetic pathways via a sequence of ThDP-bound covalent intermediates. A member of this superfamily, yeast pyruvate decarboxylase (YPDC) carries out the nonoxidative decarboxylation of pyruvate and is mechanistically a simpler ThDP enzyme. YPDC variants created by substitution at the active center (D28A, E51X, and E477Q) and on the substrate activation pathway (E91D and C221E) display varying activity, suggesting that they stabilize different covalent intermediates. To test the role of both rings of ThDP in YPDC catalysis (the 4'-aminopyrimidine as acid-base, and thiazolium as electrophilic covalent catalyst), we applied a combination of steady state and time-resolved circular dichroism experiments (assessing the state of ionization and tautomerization of enzyme-bound ThDP-related intermediates), and chemical quench of enzymatic reaction mixtures followed by NMR characterization of the ThDP-bound intermediates released from YPDC (assessing occupancy of active centers by these intermediates and rate-limiting steps). Results suggest the following: (1) Pyruvate and analogs induce active site asymmetry in YPDC and variants. (2) The rare 1',4'-iminopyrimidine ThDP tautomer participates in formation of ThDP-bound intermediates. (3) Propionylphosphinate also binds at the regulatory site and its binding is reflected by catalytic events at the active site 20 Å away. (4) YPDC stabilizes an electrostatic model for the 4'-aminopyrimidinium ionization state, an important contribution of the protein to catalysis. The combination of tools used provides time-resolved details about individual events during ThDP catalysis; the methods are transferable to other ThDP superfamily members.