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1.
Langmuir ; 40(25): 13292-13302, 2024 Jun 25.
Article in English | MEDLINE | ID: mdl-38871669

ABSTRACT

In this study, surface-enhanced Raman scattering substrates were investigated by the electrodeposition method to detect low concentrations of pesticides via the electrodeposition method with different agents from silver and gold precursors on APTES-modified ITO glass. A dual-potential method supplied three electrodes and was performed with a nucleation potential of 0.7 V for 2 s and a growth potential of -0.2 V for 500 s. The Ag film produced by the electrodeposition approach has great surface uniformity and good SERS signal amplification for the thiram insecticide at low concentrations. Interestingly, the ITO/APTES/Ag substrate extensively increased the sensitivity than the other investigated ones, thanks to the adequate assistance of amino groups of APTES in the denser and hierarchical deposition of Ag NPs. These observations were additionally elucidated via finite-difference time-domain (FDTD) calculation. For thiram, the detection was set at 10-8 M with an enhancement factor of up to 3.6 × 107 times. Comparing the SERS spectra of thiram at concentrations of 10-3, 10-4, and 10-5 M with a relative standard deviation (RSD) of less than 7.0% demonstrates excellent reproducibility of the ITO/APTES/Ag substrate. In addition, the special selectivity of the ITO/APTES/Ag substrate for thiram demonstrates that these nanostructures can identify pesticides with extreme sensitivity.

2.
Heliyon ; 10(8): e29832, 2024 Apr 30.
Article in English | MEDLINE | ID: mdl-38699708

ABSTRACT

Google Classroom is a virtual education platform created by Google that allows both instructors and learners to actively participate in educational environments inside and outside of the classroom in an innovative way. This research aims to determine how university students perceived the adoption of Google Classroom in writing classes. This research was a convergent parallel mix-methods approach in which data were gathered through a 5-point Likert scale questionnaire and semi-structured interviews. The participants of this study included 130 university students in Vietnam. The results revealed that students expressed their approval of using Google Classroom in writing classes and that they had a positive view since it benefited them greatly in their learning writing process. This study suggests practical implications for language educators to use Google Classroom in writing classes.

3.
Cancer Rep (Hoboken) ; 7(4): e2055, 2024 Apr.
Article in English | MEDLINE | ID: mdl-38577715

ABSTRACT

AIM: Sleep disorders are common in cancer patients and have negative consequences for patient well-being and treatment outcomes. This study aimed to investigate sleep quality and related factors in Vietnamese middle-aged cancer patients. METHODS: A cross-sectional study was conducted on 246 middle-aged in-patient cancer patients at Vietnam National Cancer Hospital (VNCH) from 1/2021 to 7/2021. Sleep was measured by the Pittsburgh Sleep Quality Index (PSQI), with a cutoff of 5. RESULTS: The results showed a male/female ratio of 0.85 with an average age of 52. The five most prevalent cancer types were breast, colorectal, lung, and esophagus-stomach cancer, primarily in the late stage and treated with chemotherapy. The prevalence of sleep disturbances was 58.5%. The mean PSQI score was 7.5, with sleep duration and latency of 5.4 h and 1 h, respectively. Approximately 44% of participants reported poor sleep quality, nearly 9% had daytime dysfunction, and 10.6% used sleep medication. The multivariate logistic regression results indicate that people with depression were 8.89 times more likely to have poor sleep than those without depression (95% CI:2.63-28.27, p < .001). CONCLUSION: Sleep problems are common among middle-aged people with cancer in Vietnam, especially individuals with depression. It is necessary to have more effective approaches to sleep management for cancer patients with limited resources.


Subject(s)
Neoplasms , Sleep Wake Disorders , Middle Aged , Humans , Male , Female , Cross-Sectional Studies , Vietnam/epidemiology , Cancer Care Facilities , Sleep , Neoplasms/epidemiology , Sleep Wake Disorders/epidemiology , Sleep Wake Disorders/etiology
4.
PLoS One ; 18(11): e0293033, 2023.
Article in English | MEDLINE | ID: mdl-38011050

ABSTRACT

Fintech development is generally considered as an effective mechanism to promote the consumption of renewable energy sources. The relationship between fintech development and renewable energy consumption have been examined in previous studies. However, the moderating effect of income inequality on this relationship has largely been ignored in the existing literature. As such, this study is conducted to shed light on this moderating effect. Two estimation techniques, including the two-step system generalized method of moments (GMM) and the method of moments quantile regression (MMQR), were used on a sample of 65 countries from 2013 to 2019. Our findings reveal that fintech development plays a vital role in promoting the consumption of renewable energy sources. However, it is crucial to recognize that rising income inequality may hinder the potential positive effects of fintech development on renewable energy consumption. A threshold of income inequality should be maintained to ensure that the positive effect of fintech development on increased renewable energy consumption is not compromised. Policy implications have emerged based on the findings from this study regarding promoting fintech development towards green economic growth and sustainable development.


Subject(s)
Carbon Dioxide , Income , Renewable Energy , Economic Development , Sustainable Development
5.
Heliyon ; 9(9): e19926, 2023 Sep.
Article in English | MEDLINE | ID: mdl-37809786

ABSTRACT

Flexible surface-enhanced Raman scattering (SERS) sensors have gained significant attention for their practical applications in detecting chemical and biological molecules. However, the fabrication of flexible SERS chips is often complex and requires advanced techniques. In this study, we present a simple and rapid method to design a flexible SERS chip based on polyvinyl alcohol (PVA), cellulose, and silver nanoparticles (AgNPs) using mechanical stirring and drying methods. Benefiting from the abundant hydroxide groups on cellulose, AgNPs easily adhere and distribute evenly on the cellulose surface. The combination of PVA and cellulose forms a bendable film-like SERS chip. This chip allows convenient immersion in liquid analyte samples. We demonstrate its effectiveness by using it to detect the thiram pesticide in apple juice using the "dip and dry" method, achieving an outstanding detection limit of 1.01 × 10-8 M. The Raman signals on the SERS chips exhibit high repeatability and reproducibility, with relative standard deviation values below 10%. These findings show that the flexible PVA/cellulose/Ag SERS chips is a strong candidate for real-world analysis.

6.
RSC Adv ; 13(37): 25762-25777, 2023 Aug 29.
Article in English | MEDLINE | ID: mdl-37655359

ABSTRACT

In this work, a series of unsaturated polyester resin (UPRs)/electrochemically exfoliated graphene oxide (e-GO) polymer nanocomposites with different ratios of e-GO (0.05, 0.1, 0.15, and 0.2 wt%) were prepared via an in situ polymerization method. The surface morphology and structural and chemical properties of the original UPR and UPR/e-GO nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). The positive influence of e-GO nanosheets on the mechanical properties, thermal stability, and anti-UV aging performance of UPR/e-GO nanocomposites was demonstrated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The obtained results showed that the incorporation of e-GO nanosheets within the UPR matrix, despite the addition of e-GO at as low as 0.2 wt% comprehensively improves the advanced functional properties of UPR/e-GO nanocomposites as compared to the original UPR. In addition, artificial weathering testing of quartz-based artificial stone using UPR/e-GO 0.2 wt% showed excellent UV-resistant efficiency, supporting the use of e-GO nanosheets as an additive in manufacturing the industrial-scale UPRs-based artificial quartz stone samples for real outdoor applications.

7.
Heliyon ; 9(8): e19000, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37636424

ABSTRACT

Income inequality is a vexing developmental challenge for governments and policymakers as it impedes social transformation and economic growth and development. Meanwhile, promoting financial development is generally regarded as an effective way to achieve inclusive and sustainable growth. This study examines the long-run effects of financial development, economic growth, and their combined effects on income inequality for 12 Asia-Pacific countries from 1990 to 2021. This paper employs various econometric techniques and different financial development proxies to ensure the findings' robustness. The paper also constructs a financial development index using the principal component analysis to fully capture the comprehensive effect of financial development on income inequality. Empirical results reveal that the impact of financial development on income inequality follows the inverted U-shaped relationship - financial development widens income inequality and only reduces income when surpassing its turning point. Findings further reveal that the nonlinear effect of financial development on income inequality is contingent upon the level of per capita income. Thus, policies promoting financial development to reduce income inequality should consider the existing level of per capita income.

8.
Nanomaterials (Basel) ; 13(14)2023 Jul 23.
Article in English | MEDLINE | ID: mdl-37513150

ABSTRACT

Developing highly efficient and durable hydrogen evolution reaction (HER) electrocatalysts is crucial for addressing the energy and environmental challenges. Among the 2D-layered chalcogenides, MoSe2 possesses superior features for HER catalysis. The van der Waals attractions and high surface energy, however, stack the MoSe2 layers, resulting in a loss of edge active catalytic sites. In addition, MoSe2 suffers from low intrinsic conductivity and weak electrical contact with active sites. To overcome the issues, this work presents a novel approach, wherein the in situ incorporated diethylene glycol solvent into the interlayers of MoSe2 during synthesis when treated thermally in an inert atmosphere at 600 °C transformed into graphene (Gr). This widened the interlayer spacing of MoSe2, thereby exposing more HER active edge sites with high conductivity offered by the incorporated Gr. The resulting MoSe2-Gr composite exhibited a significantly enhanced HER catalytic activity compared to the pristine MoSe2 in an acidic medium and demonstrated a superior HER catalytic activity compared to the state-of-the-art Pt/C catalyst, particularly at a high current density beyond ca. 55 mA cm-2. Additionally, the MoSe2-Gr catalyst demonstrated long-term electrochemical stability during HER. This work, thus, presents a facile and novel approach for obtaining an efficient MoSe2 electrocatalyst applicable in green hydrogen production.

9.
Chemphyschem ; 24(18): e202300210, 2023 Sep 15.
Article in English | MEDLINE | ID: mdl-37394623

ABSTRACT

In this study, the features of resistive random access memory (RRAM) employing a straightforward Cr/MAPbI3 /FTO three-layer structure have been examined and clarified. The device displays various resistance switching (RS) behavior at various sweep voltages between 0.5 and 5 V. The RS effect has a conversion in the direction of the SET and RESET processes during sweeping for a number of cycles at a specific voltage. The directional change of the RS processes corresponds to the dominant transition between the generation/recombination of iodide ion and vacancy in the MAPbI3 perovskite layer and the electrochemical metallization of the Cr electrode under the influence of an electric field, which results in the conductive filament (CF) formation/rupture. At each stage, these processes are controlled by specific charge conduction mechanisms, including Ohmic conduction, space-charge-limited conduction (SCLC), and variable-range hopping (VRH). By identifying the biased voltage and the quantity of voltage sweep cycles, one can take a new approach to control or modulate the pathways for effective charge transport. This new approach is made possible by an understanding of the RS characteristics and the corresponding mechanisms causing the variation of RS behavior in the structure.

10.
Front Pharmacol ; 14: 1127722, 2023.
Article in English | MEDLINE | ID: mdl-36959850

ABSTRACT

Receptor-interacting serine/threonine kinase 2 (RIPK2) is a vital immunomodulator that plays critical roles in nucleotide-binding oligomerization domain 1 (NOD1), NOD2, and Toll-like receptors (TLRs) signaling. Stimulated NOD1 and NOD2 interact with RIPK2 and lead to the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPK), followed by the production of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-12/23. Defects in NOD/RIPK2 signaling are associated with numerous inflammatory diseases, including asthma, sarcoidosis, inflammatory bowel disease (Crohn's disease and ulcerative colitis), multiple sclerosis, and Blau syndrome. As RIPK2 is a crucial element of innate immunity, small molecules regulating RIPK2 functions are attractive to establish novel immunotherapies. The increased interest in developing RIPK2 inhibitors has led to the clinical investigations of novel drug candidates. In this review, we attempt to summarize recent advances in the development of RIPK2 inhibitors and degraders.

11.
Cancer Control ; 29: 10732748221140206, 2022.
Article in English | MEDLINE | ID: mdl-36373740

ABSTRACT

OBJECTIVES: Though menstrual and reproductive factors have been associated with the risk of breast cancer in many populations, very few studies have been conducted among Vietnamese women. This study aimed to assess the association between menstrual and reproductive factors and the risk of breast cancer in Vietnamese women. METHODS: A retrospective case-control study of 490 breast cancer cases and 468 controls was conducted in Northern Vietnam. Unconditional logistic regression models adjusting for confounders were used to estimate odds ratios (ORs) and their 95% confidence intervals (CIs) for the associations of menstrual and reproductive factors with the risk of breast cancer; overall and by cancer subtype. RESULTS: Among breast cancer patients, the luminal B subtype was the most frequent (48.6%), followed by HER2-overexpressing (24.5%), luminal A (16.7%), and triple-negative breast cancer (TNBC; 10.2%). Among menopausal women, menopausal age at 50 years or older (OR = 1.71, 95% CI: 1.15-2.57 vs. <50 y) was associated with an increased risk of breast cancer. Earlier age at menarche (<13 y) was associated with a significantly increased risk of breast cancer (OR = 2.66, 95% CI: 1.08-7.51) among premenopausal women only and the luminal A subtype of breast cancer (OR = 3.06, 95% CI: 1.04-8.16). Having more than two children was associated with a reduced risk of premenopausal (OR = .42, 95%CI: .21-.83), luminal B (OR = .43, 95% CI: .24-.79), and TNBC (OR = .34, 95% CI: .14-.89). Later menopause was positively associated with the risk of breast cancer with HER2 overexpression (OR = 2.19, 95% CI: 1.14-4.23). CONCLUSION: Associations of menstrual and reproductive factors with breast cancer among Vietnamese women, particularly for among premenopausal women and for the luminal A subtype, are generally consistent with those reported from other countries. These findings suggest that changes in menstrual and reproductive patterns among young Vietnamese women may contribute to the recent rising incidence of breast cancer in Vietnam.


Subject(s)
Breast Neoplasms , Triple Negative Breast Neoplasms , Child , Humans , Female , Middle Aged , Breast Neoplasms/epidemiology , Breast Neoplasms/complications , Case-Control Studies , Triple Negative Breast Neoplasms/epidemiology , Retrospective Studies , Vietnam/epidemiology , Risk Factors , Asian People , Receptors, Progesterone , Receptor, ErbB-2
12.
Pol J Microbiol ; 71(3): 381-394, 2022 Sep 01.
Article in English | MEDLINE | ID: mdl-36185028

ABSTRACT

Whole-genome sequencing and genome mining are recently considered an efficient approach to shine more light on the underlying secondary metabolites of Streptomyces. The present study unearths the biosynthetic potential of endophytic SX6 as a promising source of biologically active substances and plant-derived compounds for the first time. Out of 38 isolates associated with Aegiceras corniculatum (L.) Blanco, Streptomyces parvulus SX6 was highly active against Pseudomonas aeruginosa ATCC® 9027™ and methicillin-resistant Staphylococcus epidermidis (MRSE) ATCC® 35984™. Additionally, S. parvulus SX6 culture extract showed strong cytotoxicity against Hep3B, MCF-7, and A549 cell lines at a concentration of 30 µg/ml, but not in non-cancerous HEK-293 cells. The genome contained 7.69 Mb in size with an average G + C content of 72.8% and consisted of 6,779 protein-coding genes. AntiSMASH analysis resulted in the identification of 29 biosynthetic gene clusters (BGCs) for secondary metabolites. Among them, 4 BGCs showed low similarity (28-67% of genes show similarity) to actinomycin, streptovaricin, and polyoxypeptin gene clusters, possibly attributed to antibacterial and anticancer activities observed. In addition, the complete biosynthetic pathways of plant-derived compounds, including daidzein and genistein were identified using genome mining and HPLC-DAD-MS analysis. These findings portray an exciting avenue for future characterization of promising secondary metabolites from mangrove endophytic S. parvulus.


Subject(s)
Methicillin-Resistant Staphylococcus aureus , Primulaceae , Streptomyces , Anti-Bacterial Agents/metabolism , Anti-Bacterial Agents/pharmacology , Dactinomycin/metabolism , Genistein/metabolism , HEK293 Cells , Humans , Phytochemicals , Primulaceae/metabolism , Streptovaricin/metabolism
13.
JACS Au ; 2(4): 839-852, 2022 Apr 25.
Article in English | MEDLINE | ID: mdl-35557769

ABSTRACT

Thiol-mediated uptake is emerging as a powerful method to penetrate cells. Cyclic oligochalcogenides (COCs) have been identified as privileged scaffolds to enable and inhibit thiol-mediated uptake because they can act as dynamic covalent cascade exchangers, i.e., every exchange produces a new, covalently tethered exchanger. In this study, our focus is on the essentially unexplored COCs of higher oxidation levels. Quantitative characterization of the underlying dynamic covalent exchange cascades reveals that the initial ring opening of cyclic thiosulfonates (CTOs) proceeds at a high speed even at a low pH. The released sulfinates exchange with disulfides in aprotic but much less in protic environments. Hydrophobic domains were thus introduced to direct CTOs into hydrophobic pockets to enhance their reactivity. Equipped with such directing groups, fluorescently labeled CTOs entered the cytosol of living cells more efficiently than the popular asparagusic acid. Added as competitive agents, CTOs inhibit the uptake of various COC transporters and SARS-CoV-2 lentivectors. Orthogonal trends found with different transporters support the existence of multiple cellular partners to account for the diverse expressions of thiol-mediated uptake. Dominant self-inhibition and high activity of dimers imply selective and synergistic exchange in hydrophobic pockets as distinguishing characteristics of thiol-mediated uptake with CTOs. The best CTO dimers with hydrophobic directing groups inhibit the cellular entry of SARS-CoV-2 lentivectors with an IC50 significantly lower than the previous best CTO, below the 10 µM threshold and better than ebselen. Taken together, these results identify CTOs as an intriguing motif for use in cytosolic delivery, as inhibitors of lentivector entry, and for the evolution of dynamic covalent networks in the broadest sense, with reactivity-based selectivity of cascade exchange emerging as a distinguishing characteristic that deserves further attention.

14.
JACS Au ; 1(6): 710-728, 2021 Jun 28.
Article in English | MEDLINE | ID: mdl-34467328

ABSTRACT

This Perspective focuses on thiol-mediated uptake, that is, the entry of substrates into cells enabled by oligochalcogenides or mimics, often disulfides, and inhibited by thiol-reactive agents. A short chronology from the initial observations in 1990 until today is followed by a summary of cell-penetrating poly(disulfide)s (CPDs) and cyclic oligochalcogenides (COCs) as privileged scaffolds in thiol-mediated uptake and inhibitors of thiol-mediated uptake as potential antivirals. In the spirit of a Perspective, the main part brings together topics that possibly could help to explain how thiol-mediated uptake really works. Extreme sulfur chemistry mostly related to COCs and their mimics, cyclic disulfides, thiosulfinates/-onates, diselenolanes, benzopolysulfanes, but also arsenics and Michael acceptors, is viewed in the context of acidity, ring tension, exchange cascades, adaptive networks, exchange affinity columns, molecular walkers, ring-opening polymerizations, and templated polymerizations. Micellar pores (or lipid ion channels) are considered, from cell-penetrating peptides and natural antibiotics to voltage sensors, and a concise gallery of membrane proteins, as possible targets of thiol-mediated uptake, is provided, including CLIC1, a thiol-reactive chloride channel; TMEM16F, a Ca-activated scramblase; EGFR, the epithelial growth factor receptor; and protein-disulfide isomerase, known from HIV entry or the transferrin receptor, a top hit in proteomics and recently identified in the cellular entry of SARS-CoV-2.

15.
Case Rep Oncol ; 14(2): 797-801, 2021.
Article in English | MEDLINE | ID: mdl-34248542

ABSTRACT

Pulmonary angiosarcoma is a rare clinical entity with a poor prognosis and no established therapeutic strategies. We present the first case to our knowledge of metastatic pulmonary angiosarcoma, treated with checkpoint inhibitor immunotherapy, and have an excellent response. Until now, patient has been treated with immunotherapy for 1 year, and his disease is stable and well-tolerated.

16.
PLoS One ; 15(12): e0243286, 2020.
Article in English | MEDLINE | ID: mdl-33270761

ABSTRACT

In vitro and ex vivo development of novel therapeutic agents requires reliable and accurate analyses of the cell conditions they were preclinical tested for, such as apoptosis. The detection of apoptotic cells by annexin V (AV) coupled to fluorophores has often shown limitations in the choice of the dye due to interference with other fluorescent-labeled cell markers. The SNAP-tag technology is an easy, rapid and versatile method for functionalization of proteins and was therefore used for labeling AV with various fluorophores. We generated the fusion protein AV-SNAP and analyzed its capacity for the specific display of apoptotic cells in various assays with therapeutic agents. AV-SNAP showed an efficient coupling reaction with five different fluorescent dyes. Two selected fluorophores were tested with suspension, adherent and peripheral blood cells, treated by heat-shock or apoptosis-inducing therapeutic agents. Flow cytometry analysis of apoptotic cells revealed a strong visualization using AV-SNAP coupled to these two fluorophores exemplary, which was comparable to a commercial AV-Assay-kit. The combination of the apoptosis-specific binding protein AV with the SNAP-tag provides a novel solid method to facilitate protein labeling using several, easy to change, fluorescent dyes at once. It avoids high costs and allows an ordinary exchange of dyes and easier use of other fluorescent-labeled cell markers, which is of high interest for the preclinical testing of therapeutic agents in e.g. cancer research.


Subject(s)
Apoptosis/physiology , Fluorescent Dyes/chemistry , Staining and Labeling/methods , Affinity Labels/chemistry , Annexin A5/chemistry , Annexin A5/metabolism , Blood Cells/metabolism , Cell Line, Tumor , Flow Cytometry/methods , Humans , Neoplasms/metabolism , Proteins/chemistry , Proteins/metabolism , Technology
17.
Chem Asian J ; 15(10): 1562-1566, 2020 May 15.
Article in English | MEDLINE | ID: mdl-32311232

ABSTRACT

We report design, synthesis and evaluation of a series of naphthalenediimides (NDIs) that are bridged with short peptides. Reminiscent of peptide stapling technologies, the macrocycles are conveniently accessible by a chromogenic nucleophilic aromatic substitution of two bromides in the NDI core with two thiols from cysteine sidechains. The dimension of core-bridged NDIs matches that of one turn of an α helix. NDI-stapled peptides exist as two, often separable atropisomers. Introduction of tertiary amine bases in amino-acid sidechains above the π-acidic NDI surface affords operational anion-π catalysts. According to an enolate chemistry benchmark reaction, anion-π catalysis next to peptides occurs with record chemoselectivity but weak enantioselectivity. Catalytic activity drops with increasing distance of the amine base to the NDI surface, looser homocysteine bridges, mismatched, shortened and elongated α-helix turns, and acyclic peptide controls. Elongation of isolated turns into short α helices significantly increases activity. This increase is consistent with remote control of anion-π catalysis from the α-helix macrodipole.


Subject(s)
Imides/chemistry , Naphthalenes/chemistry , Peptides/chemistry , Anions/chemistry , Catalysis , Imides/chemical synthesis , Models, Molecular , Molecular Conformation , Naphthalenes/chemical synthesis
18.
Chem Sci ; 12(2): 626-631, 2020 Nov 18.
Article in English | MEDLINE | ID: mdl-34163793

ABSTRACT

Ellman's reagent has caused substantial confusion and concern as a probe for thiol-mediated uptake because it is the only established inhibitor available but works neither efficiently nor reliably. Here we use fluorescent cyclic oligochalcogenides that enter cells by thiol-mediated uptake to systematically screen for more potent inhibitors, including epidithiodiketopiperazines, benzopolysulfanes, disulfide-bridged γ-turned peptides, heteroaromatic sulfones and cyclic thiosulfonates, thiosulfinates and disulfides. With nanomolar activity, the best inhibitors identified are more than 5000 times better than Ellman's reagent. Different activities found with different reporters reveal thiol-mediated uptake as a complex multitarget process. Preliminary results on the inhibition of the cellular uptake of pseudo-lentivectors expressing SARS-CoV-2 spike protein do not exclude potential of efficient inhibitors of thiol-mediated uptake for the development of new antivirals.

19.
J Anal Methods Chem ; 2019: 8639528, 2019.
Article in English | MEDLINE | ID: mdl-30993029

ABSTRACT

The electrochemical behaviour of auramine O on the hanging mercury drop electrode has been investigated by cyclic and square wave voltammetry method. Reduction peak of auramine O was irreversible and adsorptive on the hanging mercury drop electrode. The optimal conditions were chosen to be Briton-Robinson buffer pH 9.0, accumulation potential -0.5 V vs. Ag/AgCl/KCl, accumulation time 60 s, pulse amplitude 250 mV·s-1, and frequency 50 Hz. At the optimum experimental conditions, the peak of the target analyte was sharp and asymmetric. The linearity of the peak current depending on the concentration ranged from 4.0 × 10-8 to 6.4 × 10-7 mol L-1. The limit of detection and limit of quantitation were 2.46 × 10-8 mol L-1 and 8.21 × 10-8 mol L-1, respectively. The recovery and relative standard deviation were 94.9% and 2.0% (n = 5). The developed method was successfully applied to determine auramine O in chicken samples with an appropriate sample preparation.

20.
J Am Chem Soc ; 140(51): 17867-17871, 2018 12 26.
Article in English | MEDLINE | ID: mdl-30543410

ABSTRACT

Epoxide-opening ether cyclizations are shown to occur on π-acidic aromatic surfaces without the need of additional activating groups and with autocatalytic amplification. Increasing activity with the intrinsic π acidity of benzenes, naphthalenediimides (NDIs) and perylenediimides (PDIs) support that anion-π interactions account for function. Rate enhancements maximize at 270 for anion-π catalysis on fullerenes and at 5100 M-1 for autocatalysis. The occurrence of anion-π autocatalysis is confirmed with increasing initial rates in the presence of additional product. Computational studies on autocatalysis reveal transition state and product forming a hydrogen-bonded noncovalent macrocycle, like holding their hands and dancing on the active π surface, with epoxide opening and nucleophile being activated by anion-π interactions and hydrogen bonds to the product, respectively.

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