EEG characteristic analysis of coach bus drivers based on brain connectivity as revealed via a graph theoretical network

This study describes the detection of driving fatigue using the characteristics of brain networks in a real driving environment. First, the θ, β and 36–44 Hz rhythm from the EEG signals of drivers were extracted using wavelet packet decomposition (WPD). The correlation between EEG channels was calculated using a Pearson correlation coefficient and subsequently, the brain networks were built. Furthermore, the clustering coefficient (C) and global efficiency (G) of the complex brain networks were calculated to analyze the functional differences in the brains of drivers over time. Combined with the relative power spectrum ratio (β/θ) of EEG signals and the mean value from questionnaires, the correlation of data characteristics between brain networks and subjective and objective data was analyzed. The results show that changes in the fatigue state of drivers can be effectively detected by calculating the data characteristics of brain networks in a real driving environment.

This study describes the detection of driving fatigue using the characteristics of brain networks in a real driving environment.     

Synthesis of 2-ethoxycarbonylthieno[2,3-b]quinolines in biomass-derived solvent γ-valerolactone and their biological evaluation against protein tyrosine phosphatase 1B

A series of 2-ethoxycarbonylthieno[2,3-b]quinolines were synthesized in the bio-derived “green” solvent γ-valerolactone (GVL) and evaluated for their inhibitory activities against PTP1B, the representative compound 6a displayed an IC₅₀ value of 8.04 ± 0.71 μM with 4.34-fold preference over TCPTP. These results provided novel lead compounds for the design of inhibitors of PTP1B as well as other PTPs.

A series of 2-ethoxycarbonylthieno[2,3-b]quinolines were synthesized in the bio-derived “green” solvent γ-valerolactone and evaluated for their inhibitory activities against PTP1B, compound 6a displayed an IC₅₀ value of 8.04 ± 0.71 μM with 4.34-fold preference over TCPTP.     

An umpolung reaction of α-iminothioesters possessing a cyclopropyl group

An umpolung N-alkylation reaction of α-cyclopropyl α-iminothioesters with diethylaluminum chloride or ethylmagnesium bromide affords the corresponding N-ethylated α-aminothioesters in good yields. Subsequent oxidation and reaction of the N-ethylated product with a thiolate or a chloride anion proceed effectively to give the ring-opened products in good yields. In contrast, relatively “hard” nucleophiles did not give the ring-opened products but gave the addition products to the iminium carbon.

Tandem N-alkylation/oxidation/second addition reaction to α-cyclopropyl α-imino(thio)esters gave N-alkylated ring-opened products in good yields.     

Synthesis of tetrahydro-β-carbolines from 2-indolylmethyl azides and propargylic alcohols

A facile and efficient route to tetrahydro-β-carbolines from 2-indolylmethyl azides and propargylic alcohols via acid-catalyzed dehydrative annulation reactions is described. This reaction proceeds through a cascade sequence of Friedel–Crafts-type alkylation followed by intramolecular “Click” reaction, involving the formation of multiple chemical bonds in a single operation with excellent atom-economy and broad functional group tolerance.

The synthesis of tetrahydro-β-carbolines from 2-indolylmethyl azides and propargylic alcohols via acid-catalyzed dehydrative [4 + 2]-annulation reaction is described.     

Synthesis of benzoin under supramolecular catalysis involving cyclodextrins in water: application for the preparation of the antiepileptic drug phenytoin

Among the cyclodextrins screened for the synthesis of 2-hydroxy-1,2-diphenylethanone (benzoin) in water, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) exhibited the highest yield in the benzoin condensation reactions, and HP-β-CD can be recycled several times with little loss of activity through the addition of fresh VB₁. As an example of supramolecular catalysis, the methodology was applied to the “green” synthesis of the antiepileptic drug phenytoin through benzoin condensation, oxidation, and cyclization reactions in the presence of HP-β-CD, without the use of any harmful organic solvent. Moreover, the complexation behaviors of HP-β-CD with benzaldehyde and intermediates were studied by UV-vis and 2D-ROESY NMR spectroscopies to reveal the plausible mechanisms of the reactions, and HP-β-CD did not act as a simple phase transfer agent.

Benzoin was synthesized using cyclodextrins as phase transfer catalysts. As an example of supramolecular catalysis, the methodology was applied to the “green” synthesis of the antiepileptic drug Phenytoin in the presence of HP-β-CD.     

Validation of an insertion-engineered isoprene synthase as a strategy to functionalize terpene synthases

Terpene synthases are biotechnologically-relevant enzymes with a variety of applications. However, they are typically poor catalysts and have been difficult to engineer. Structurally, most terpene synthases share two conserved domains (α- and β-domains). Some also contain a third domain containing a second active site (γ-domain). Based on the three-domain architecture, we hypothesized that αβ terpene synthases could be engineered by insertion of a heterologous domain at the site of the γ-domain (an approach we term “Insertion-engineering terpene synthase”; Ie-TS). We demonstrate that by mimicking the domain architecture of αβγ terpene synthases, we can redesign isoprene synthase (ISPS), an αβ terpene synthase, while preserving enzymatic activity. Insertion of GFP or a SpyCatcher domain within ISPS introduced new functionality while maintaining or increasing catalytic turnover. This insertion-engineering approach establishes that the γ-domain position is accessible for incorporation of additional sequence features and enables the rational engineering of terpene synthases for biotechnology.

“Insertion-engineering” approach allows for the modification of αβ terpene synthases.     

Non-Kolbe electrolysis of N-protected-α-amino acids: a standardized method for the synthesis of N-protected (1-methoxyalkyl)amines

Here, we report a standardized method for the synthesis of N-protected (1-methoxyalkyl)amines by the electrochemical decarboxylative α-methoxylation of α-amino acid derivatives using the commercially available, easy-to-use, compact ElectraSyn 2.0 setup. The use of equipment with a standardized power source, electrodes, and other accessories allows this experimental procedure to be easily transferred to any laboratory in the world. A simple workup and chromatography-free purification produced the products in excellent yields above 90%.

A high-yielding, standardized, electrochemical method for the synthesis of N-protected (1-methoxyalkyl)amines using commercially available, user-friendly kit – not only for “electro-curious” chemists.     

A double fluorescent nanoprobe based on phosphorus/nitrogen co-doped carbon dots for detecting dichromate ions and dopamine

An “on–off–on” fluorescent phosphorus/nitrogen co-doped carbon dot (PNCD) probe was explored for the determination of Cr(vi) and dopamine resulting from the inner filter effect (IFE). The blue-emitting carbon dots with high quantum yields of 25.47% as well as a narrow size distribution were synthesized by a rapid, convenient route using H₃PO₄ and ethylenediamine as the precursors without any surface passivation. A wide linear region in the range of 7–70 μM with a detection limit of 0.71 μM was achieved for Cr(vi). Moreover, the proper reductants can weaken the inner filter effect to recover the PNCD fluorescence by converting Cr(vi) into Cr(iii). Therefore, the PNCDs/Cr(vi) hybrid could also be used as an “off–on” fluorescent probe for detecting dopamine (DA) with a detection limit of 0.49 μM. Consequently, the PNCDs could serve as a powerful fluorescent bi-sensor for detection of both Cr(vi) and DA in practical applications.

An “on–off–on” fluorescent phosphorus/nitrogen co-doped carbon dot (PNCD) probe was explored for the determination of Cr(vi) and dopamine resulting from the inner filter effect (IFE).     

Error or exemption to the rule? Development of a diagnostic check for thermochemistry of metal–organic compounds

Volatile metal β-diketonates are well-known precursors used in Metal–Organic Chemical Vapour Deposition (MOCVD) for manufacturing film materials. Knowledge of vapour pressures and sublimation/vaporization thermodynamics of the MOCVD precursors is indispensable for optimization of deposition. However, the spread of available data could be unacceptably large for the same precursor for several reasons related to its chemical nature or incorrectly configured conditions of tensimetric investigation. In this work, we have developed an algorithm for a general diagnostic check, based on principles of group-additivity, for thermochemistry on solid–gas, liquid–gas, and solid–liquid phase transitions of metal–organic compounds and applied it to tris(beta-diketonato)iron complexes. The diagnostic tool helps to localize general “healthy” thermochemical interconnected data, and, subsequently, isolate molecules with definitely “ill” properties from the data pool. This diagnostic tool could be expanded and adapted for β-diketonate complexes with metals other than iron.

A diagnostic tool for checking the consistency of thermochemical data of tris(beta-diketonato)metal complexes is developed.     

Novel oligopeptide nanoprobe for targeted cancer cell imaging

Here we designed and constructed a tryptophan-phenylalanine-phenylalanine-tryptophan (WFFW) tetrapeptide, which generated photostable and tunable fluorescence emission signals from 340 nm to 500 nm. The WFFW tetrapeptide could self-assemble into a spherical nanostructure with enhanced fluorescence intensity. Driven by π–π stacking and hydrogen bond interaction, WFFW co-assembled with arginine-glycine-aspartic acid (RGD) modified WFFW to form a cancer-targeted fluorescent nanoprobe, which could selectively image the cancer cells.

Co-assembly of WFFW tetrapeptide and RGDWFFW heptapeptide generated the photostable and fluorescence-tunable nanoprobe, which could selectively image the cancer cells.     

Structure-flexible DNA origami translocation through a solid-state nanopore

Nanopore detection is a label-free detection method designed to analyze single molecules by comparing specific translocation events with high signal-to-noise ratios. However, it is still challenging to understand the influences of structural flexibility of 100 nm DNA origami on nanopore translocations. Here, we used solid-state nanopores to characterize the translocation of “nunchaku” origami structures, the flexibility of which can be regulated by introducing specific DNA strands and streptavidin protein. The structural changes can result in significant variations in the translocation signals and distributions. It is anticipated that such a method of the flexible DNA origami translocation through a solid-state nanopore will find further applications in molecular detection as well as biosensing.

Using a solid-state nanopore to characterize the translocation of “nunchaku” origami with tunable-structures.     

Effects of critical interfacial shear strength between a polymer matrix and carbon nanotubes on the interphase strength and Pukanszky's “B” interphase parameter

In this paper, the “B” interphase parameter in the Pukanszky model and interphase strength for polymer carbon nanotube (CNT) nanocomposites are expressed by the critical interfacial shear strength (τ_c) and interfacial shear strength (τ) between a polymer matrix and CNTs. A suggested model and a developed Pukanszky model for tensile strength of nanocomposites are combined to develop the equations for “B” and interphase strength. Many experimental data for various samples confirm the models. The impacts of all parameters on the “B” and interphase strength are explained to approve the developed equations. The contour plots display the same trends for the roles of all parameters in the “B” and interphase strength. Low “τ_c”, high “τ”, thin and large CNTs as well as a dense interphase are ideal to obtain the high levels for “B” and interphase strength. Among the studied parameters, CNT size largely controls the “B” and interphase strength, while the waviness and strength of CNTs play insignificant roles.

In this paper, the “B” interphase parameter in the Pukanszky model and interphase strength for polymer carbon nanotube (CNT) nanocomposites are expressed by the critical interfacial shear strength (τ_c) and interfacial shear strength (τ) between a polymer matrix and CNTs.     

Insights into a novel class of azobenzenes incorporating 4,6-O-protected sugars as photo-responsive organogelators

A novel class of 4,6-O-butylidene/ethylidene/benzylidene β-d-glucopyranose gelator functionalized with photo-responsive azobenzene moieties were designed and synthesized and also characterized using different spectral techniques. These azobenzene-based organogelators can gel even at lower concentrations (critical gelation concentration – 0.5% and 1%). A morphological study of the gels shows one-dimensional aggregated bundles and helical fibres. The main driving force for the self-assembly is through cooperative interactions exhibited by the different groups viz., sugar hydroxyl (hydrogen bonding interaction), azobenzene (aromatic π–π interaction) and alkyl chain of the protecting group (van der Waals interaction).

A novel class of 4,6-O-butylidene/ethylidene/benzylidene β-d-glucopyranose gelator functionalized with photo-responsive azobenzene moieties were designed and synthesized and also characterized using different spectral techniques.     

Cytidine-stabilized copper nanoclusters as a fluorescent probe for sensing of copper ions and hemin

We reported a sensitive and selective fluorescence “turn on–off” strategy for detection of Cu²⁺ and hemin, respectively. The fluorescence “turn on” sensor for Cu²⁺ detection had a wide linear range of 0.05–2.0 μM with a limit of detection (LOD) of 0.032 μM, and the fluorescence “turn off” sensor for hemin detection possessed a wide linear range of 0.05–4.0 μM with an LOD of 0.045 μM. The sensor for Cu²⁺ or hemin exhibited high selectivity over other possible substances. In addition, it was demonstrated by using various analytical characterization techniques that the fluorescence “turn on” sensor for Cu²⁺ was constructed on the basis of the formation of water-soluble fluorescent copper nanoclusters (CuNCs), and the fabrication of the fluorescence “turn off” sensor for hemin was predominately based on the inner filter effect of hemin on the fluorescence of the CuNCs. Finally, the proposed fluorescence “turn on–off” sensor system was successfully applied for detection of Cu²⁺ in lake water samples and hemin in duck blood samples.

A sensitive and selective fluorescence “turn on–off” strategy for simultaneous detection of Cu²⁺ and hemin was proposed on the basis of the formation of fluorescent CuNCs and the inner filter effect of hemin on the fluorescence of the CuNCs.     

A “Turn-On” fluorescent probe for sensitive and selective detection of fluoride ions based on aggregation-induced emission

Based on the fluorophore of 2-(2′-hydroxyphenyl)benzothiazole (HBT) with aggregation-induced emission (AIE) properties, a highly selective and sensitive fluorescent probe PBT towards F⁻ was investigated. “Turn-On” fluorescence type signaling was realized by employing fluoride-selective cleavage of the latent thiophosphinated probe in mixed aqueous media. The probe is designed in such a way that the excited state intramolecular proton transfer (ESIPT) of the HBT moiety becomes blocked. The chemodosimetric approach of F⁻ to the probe results in the recovery of the ESIPT by removal of a free AIE-active HBT moiety through a subsequent hydrolysis process. The F⁻ detection limit of the probe was 3.8 nM in the dynamic range of 0.5 μM to 10 μM. In addition, the proposed probe has been used to detect F⁻ in water samples and toothpaste samples with satisfying results.

A “Turn-On” fluorescent probe PBT for sensitive and selective detection of fluoride ions based on aggregation-induced emission.     

Unique indolizidine alkaloid securinine is a promising scaffold for the development of neuroprotective and antitumor drugs

Alkaloids, secondary plant metabolites, are used in traditional medicine in many countries to treat various pathological conditions. Securinine, a unique indolizidine alkaloid combining four cycles, “6-azobicyclo[3.2.1]octane” as a key structure fused with α,β-unsaturated-γ-lactone and piperidine ring, has a broad spectrum of actions including anti-inflammatory, antibacterial, neuroprotective and antitumor, and has been previously used in medical practice. It has several reactive centers, which are double bonds at positions 12–13 and 14–15, and this is a challenging scaffold for the synthesis of biologically active compounds. In this review, works on the production of modified securinine derivatives and their biological activity are addressed. Both monovalent and bivalent derivatives that are most promising in our opinion, and have potential for further research, are considered.

Derivatives of unique indolizidine alkaloid securinine used for neuroprotection and as antitumor agents.     

Facile synthesis of carbon nitride quantum dots as a highly selective and sensitive fluorescent sensor for the tetracycline detection

Enhanced blue fluorescent carbon nitride quantum dots (g-C₃N₄QDs) were synthesized by a simple solvothermal “tailoring” process from bulk g-C₃N₄ and analyzed by various characterization methods. The as-obtained g-C₃N₄QDs were successfully applied in the determination of tetracycline (TC) with a good linear relationship in the range of 0.23–202.70 μM. The proposed fluorescent sensor shows excellent stability, good repeatability, high selectivity and outstanding sensitivity to TC with a low detection limit of 0.19 μM. The fluorescence quenching mechanism of g-C₃N₄QDs with TC was mainly governed by static quenching and the inner filter effect. The method was successfully applied to monitor TC in tap water and milk powder samples.

The g-C₃N₄QDs were synthesized by a simple solvothermal “tailoring” process from bulk g-C₃N₄ which have a “strong quenching” behaviour in the presence of TC. The proposed fluorescent sensor has been successfully applied to detect TC in actual samples.     

Fluorescence detection of fluorine ions in biological fluids based on aggregation-induced emission

Traditional chemical and biological sensors developed through aggregation-induced emission (AIE) are mainly based on “Turning on” pattern of fluorescence enhancement, which often has poor selectivity and can be easily interfered with by other substances. On this basis, an AIE-based tetraphenyl ethylene (TPE) derivative (TPE-COOH) was prepared in this study and aggregated by adding Al³⁺, so as to form the TPE-COOH/Al³⁺ polymer. TPE-COOH fluorescence was enhanced through AIE principle, thus realizing the “Turning on” state. F⁻ could bind to Al³⁺ after the addition of F⁻ ions which would result in the decomposition of TPE-COOH/Al³⁺ aggregate, dissolved state of TPE-COOH and gradual reduction of fluorescence intensity of the system, thus realizing “Turning off” state. Moreover, F⁻ ions in biological fluid were analyzed and detected through such AIE-based “Turning on-off” pattern. The linear range of this method for F⁻ detection was 3–12 μM and the detection limit was 0.9 μM.

Schematic diagram of fluorescence detection of F⁻ ions in biological fluids based on TPE-COOH/Al³⁺ polymer Aggregation-Induced Emission (AIE) “Turning on–off” mode.     

An ‘‘off–on–off’’ sensor for sequential detection of Cu2+ and hydrogen sulfide based on a naphthalimide–rhodamine B derivative and its application in dual-channel cell imaging

A novel colorimetric and fluorometric sensor with unique dual-channel emission to sequentially detect Cu²⁺ and hydrogen sulfide (H₂S) was synthesized from naphthalimide–rhodamine B through the PET and FRET mechanism. The sensor showed a selective “off–on” fluorescence response with a 120-fold increase toward Cu²⁺, and its limits of detection were 0.26 μM and 0.17 μM for UV-vis and fluorescence measurements, respectively. In addition, 1–Cu²⁺ was an efficient “on–off” sensor to detect H₂S with detection limits of 0.40 μM (UV-vis measurement) and 0.23 μM (fluorescence measurement), respectively. Furthermore, the sensor can also be used for biological imaging of intracellular staining in living cells. Therefore, the sensor should be highly promising for the detection of low level Cu²⁺ and H₂S with great potential in many practical applications.

A novel colorimetric and fluorometric sensor with unique dual-channel emission to sequentially detect Cu²⁺ and hydrogen sulfide (H₂S) was synthesized from naphthalimide–rhodamine B through the PET and FRET mechanism.     

Studies on a glutathione coated hollow ZnO modified glassy carbon electrode; a novel Pb(ii) selective electrochemical sensor

Herein, we report the electrochemical detection of heavy metal ions such as Pb(ii), Cd(ii) and Hg(ii) ions while using glutathione coated hollow ZnO modified glassy carbon electrode (Glu-h-ZnO/GCE). An excellent voltammetric response of the modified electrode towards these metal ions was observed by different voltammetric techniques. Among the different target metal ions, a selective electrochemical response (sensitivity = 4.57 μA μM⁻¹) for the detection of Pb(ii) ions was obtained with differential pulse voltammetric (DPV) measurements. Besides, under optimal experimental conditions and in the linear concentration range of 2–18 μM, a very low detection limit of 0.42 μM was obtained for Pb(ii) ion. The observed electrochemical behaviour of Glu-h-ZnO/GCE towards these metal ions is in conformity with the band gap of the composite in the presence of various test metal ions. The band gap studies of the composite and various “Composite-Metal Ion” systems were obtained by reflectance as well as by computational methods where results are in close agreement, justifying the observed electrochemical behaviour of the systems. The lowest band gap value of the “Composite-Pb” system may be the reason for the excellent electrochemical response of the Glu-h-ZnO modified GCE towards the detection of Pb(ii) ion.

Decrease in the band gap of the "Composite-Metal" systems in comparison to pure composite is a key factor in the electrochemical detection of heavy metal ions such as Pb(ii), Cd(ii) and Hg(ii) ions while using glutathione coated hollow ZnO modified glassy carbon electrode (Glu-h-ZnO/GCE).