Four Undescribed Pyranones from the Scutellaria formosana-Derived Endophytic Fungi Ascomycota sp. FAE17.

Four undescribed pyranone derivatives, named ascomycopyrones A-D (1-4), as well as one known analogue simplicilopyrone (5) (this is the first study to report the absolute configuration), were isolated from the endophytic fungus Ascomycota sp. FAE17 derived from the flowers of Scutellaria formosa. The structures of these pyranones were identified by comprehensive spectroscopic and MS analyses, and the absolute configurations were determined by their experimental and quantum chemical electronic circular dichroism (ECD) calculations. All isolated compounds were tested for various bioactivities, including antibacterial, cytotoxic activity, and NO inhibitory activity. Unfortunately, none of the compounds showed significant bioactivities.

Flavonoidal alkaloids from the flowers of Chromolaena odorata (L.) R.M.King & H.Rob.

A pair of epimers of flavonoid alkaloids, with a pyrrolidone moiety, 2S,5''R-eupodoratin A (1), 2S,5''S-eupodoratin A (2), together with two known analogues, drahebephin A (3), drahebephin B (4), were isolated from the flowers of Chromolaena odorata (L.) R.M.King & H.Rob. Their structures were elucidated on the basis of HR-ESI-MS, 1D/2D NMR spectral analyses. The absolute configuration of compounds (1) and (2) was determined by its experimental and calculated electronic circular dichroism (ECD) spectra. All compounds were isolated from the Asteraceae family for the first time. The ABTS·+ scavenging activity of compound (4) reached 93.56% at a concentration of 0.5 mM, while the scavenging capacity of positive control Trolox was 55.94%. In addition, all compounds show moderate antimicrobial activity against Escherichia coli (ATCC, 337304), Staphylococcus aureus (ATCC, 337371) and Candida albicans (ATCC, 186382) with a MIC value of more than 50 µg/mL.

Two new lactam derivatives from a Sphagneticola trilobata derived fungus Penicillium rubens PQJ-2.

A new bicyclic lactam derivatives penicilactam B (1) and a new monocyclic amide penicillamide D (2), along with four known compounds (3-6), were isolated from the fermentation broth of the derived fungus Penicillium rubens PQJ-2. Their structures and stereochemistry were elucidated by comprehensive spectroscopic analyses and quantum ECD calculations. All the compounds were evaluated for their antibacterial activities against Staphylococcus aureus subsp, Candida albicans, Escherichia coli and insecticidal activity against Helicoverpa armigera Hubner. Compounds 1-3 exhibited modest insecticidal activity against H. armigera Hubner.

Ag and TiO2 nanoparticles co-modified defective zeolite TS-1 for improved photocatalytic CO2 reduction.

Photocatalytic CO2 reduction into fuels has been an attractive research topic. Herein, Ag and TiO2 nanoparticles co-loaded zeolite TS-1 (Ag-TiO2/TS-1) were synthesized by the ion-exchange and subsequently in-situ photodeposition method. The obtained Ag-TiO2/TS-1 sample has a high surface area and rich Ti3+-Vo defects and as well as highly dispersed Ag nanoparticles. As expected, the sample Ag-TiO2/TS-1 not only shows high CO2 adsorption capacity, but also improves the separation efficiency of photogenerated electron-hole pairs. As a result, only CO and CH4 can be detected on the sample Ag-TiO2/TS-1 in the photocatalytic CO2 conversion, and the competing H2 evolution can be completely suppressed, suggestive of its high selectivity. The super photocatalytic activity toward CO2 reduction can be ascribed to the synergistic effect among highly dispersed Ag nanoparticle, the support zeolite TS-1 and TiO2 with highly exposed {101} planes.

The computational and experimental studies on a 1, 2, 3-triazole compound and its special binding to three kinds of blood proteins.

A newly synthesized compound, ethyl 5-phenyl-2-(p-tolyl)-2H-1, 2, 3-triazole-4-carboxylate (EPPC) may be considered as a drug candidate and was exploited to study the structural and spectral properties by using quantum chemical calculation and multiple spectroscopic techniques. The results on theoretical spectrum of EPPC were consistent with experimental spectrum in great degree. In addition, EPPC has been as a special probe and investigated on the interactions with three kinds of blood proteins including human serum albumin (HSA), human immunoglobulin (HIgG) and bovine hemoglobin (BHb) by using UV-Vis, fluorescence spectroscopy and molecular modeling, respectively. Changes in various fluorescence and UV-Vis spectra were observed upon ligand binding along with a remarkable degree of fluorescence enhancement on complex formation under physiological condition with binding constant about 105 order of magnitudes, which caused the variations of conformation and microenvironment of these proteins in aqueous solution. The obtained results from the thermodynamic parameters calculated according to the van't Hoff equation indicated that the entropy change ΔS° and enthalpy change ΔH° were found to be 0.168 KJ/mol K and 22.154 KJ/mol for EPPC-HSA system, 0.284 KJ/mol K and 54.408 KJ/mol for EPPC-HIgG system, and 0.228 KJ/mol K and 37.548 KJ/mol for EPPC-BHb system, respectively, which demonstrated that the primary binding pattern is determined by hydrophobic interaction. The results of docking and molecular dynamics simulation using three proteins crystal models revealed that EPPC could bind to three proteins well into hydrophobic cavity, which showed good consistence with the spectroscopic measurements.Communicated by Ramaswamy H. Sarma.

Evolution of diffusion and structure of six n-alkanes in carbon dioxide at infinite dilution over wide temperature and pressure ranges: a molecular dynamics study.

Over wide temperature and pressure ranges, the molecular dynamics simulation is performed to study the mass transfer of six n-alkanes from n-C5H12 to n-C10H22 in CO2 at infinite dilution by calculating the diffusion coefficients, which have not yet been measured by experiment. Meanwhile, the structural properties of these systems are explored. It is found that under different temperature and pressure conditions, the variation trends of the radial distribution functions of n-alkanes are quite different, while the variation trends of the average coordination number of n-alkanes can be divided into three types. The radius of gyration and the solvent accessible surface area are both affected by temperature and carbon chain length, but their variation trends are different, and it could explain the abnormal variation trends of the radial distribution functions and the average coordination number. Graphical abstract Over wide temperature and pressure ranges, the variation trends of the average coordination number of n-alkanes can be divided into three types.

MD simulation study of the diffusion and local structure of n-alkanes in liquid and supercritical methanol at infinite dilution.

The diffusion coefficients of 14 n-alkanes (ranging from methane to n-tetradecane) in liquid and supercritical methanol at infinite dilution (at a pressure of 10.5 MPa and at temperatures of 299 K and 515 K) were deduced via molecular dynamics simulations. Values for the radial distribution function, coordination number, and number of hydrogen bonds were then calculated to explore the local structure of each fluid. The flexibility of the n-alkane (as characterized by the computed dihedral distribution, end-to-end distance, and radius of gyration) was found to be a major influence and hydrogen bonding to be a minor influence on the local structure. Hydrogen bonding reduces the flexibility of the n-alkane, whereas increasing the temperature enhances its flexibility, with temperature having a greater effect than hydrogen bonding on flexibility. Graphical abstract The flexibility of the alkane is a major influence and the hydrogen bonding is a minor influence on the first solvation shell; the coordination numbers of long-chain n-alkanes in the first solvation shell are rather low.

The characterization of 1-(4-bromophenyl)-5-phenyl-1H-1,2,3-triazole on acute toxicity, antimicrobial activities, photophysical property, and binding to two globular proteins.

1-(4-Bromophenyl)-5-phenyl-1H-1,2,3-triazole (BPT) was a newly synthesized compound. The acute toxicities of BPT to mice by intragastric administration have been determined and the result indicates that the intragastric administration of BPT did not produce any significant toxic effect on Kunming strain mice. It is also evaluated for the antimicrobial activity of BPT against three kinds of plant mycoplasma, Fusarium Wilt (race 4), Colletotrichum gloeosporioides Penz. and Xanthomonas oryzae by different method in vitro. The compound exhibited distinct inhibitory activities against Fusarium Wilt (race 4) and Colletotrichum gloeosporioides Penz. by mycelium growth rate test and the values of EC50 were 29.34 and 12.53µg/mL respectively. And BPT had also the most potent inhibitory activities against Xanthomonas oryzae when compared with that of control drugs by the agar well diffusion method. In addition, the structural and photophysical properties of BPT including ionization energy, electron affinities, and theoretical spectrum was studied by quantum-chemical methods. Then the interaction of BPT with two kinds of globular proteins, human immunoglobulin (HIg) and bovine hemoglobin (BHg) was investigated by using UV-vis absorption spectra, synchronous fluorescence, 3D fluorescence spectra, and fluorescence titration in combination with molecular modeling. UV-vis absorption, 3D and synchronous fluorescence measurements show that BPT has influence on the microenvironment surrounding HIg or BHg in aqueous solution and the fluorescence experiments show that BPT quenches the fluorescence intensity of HIg or BHg through a static mechanism. The binding parameters including the binding constants, the number of binding site and average binding distance between BPT and HIg or BHg at different temperatures were calculated. The thermodynamic parameters suggest that the hydrophobic interaction is the predominant intermolecular forces in stabilizing the BPT-HIg or BPT-BHg complex. Molecular docking was performed to reveal that the BPT moiety binds to the hydrophobic cavity of HIg or BHg and they are in good agreement with the spectroscopic measurements.

Electrochemical deoxyribonucleic acid biosensor based on electrodeposited graphene and nickel oxide nanoparticle modified electrode for the detection of salmonella enteritidis gene sequence.

In this paper a new electrochemical DNA biosensor was prepared by using graphene (GR) and nickel oxide (NiO) nanocomposite modified carbon ionic liquid electrode (CILE) as the substrate electrode. GR and NiO nanoparticles were electrodeposited on the CILE surface step-by-step to get the nanocomposite. Due to the strong affinity of NiO with phosphate groups of ssDNA, oligonucleotide probe with a terminal 5'-phosphate group could be attached on the surface of NiO/GR/CILE, which could further hybridize with the target ssDNA sequence. Methylene blue (MB) was used as the electrochemical indicator for monitoring the hybridization reaction. Under the optimal conditions the reduction peak current of MB was proportional to the concentration of salmonella enteritidis gene sequence in the range from 1.0×10(-13) to 1.0×10(-6)molL(-1) with a detection limit as 3.12×10(-14)molL(-1). This electrochemical DNA sensor exhibited good discrimination ability to one-base and three-base mismatched ssDNA sequences, and the polymerase chain reaction amplification product of salmonella enteritidis gene sequences were further detected with satisfactory results.

Application of graphene-copper sulfide nanocomposite modified electrode for electrochemistry and electrocatalysis of hemoglobin.

In this paper a graphene (GR) and copper sulfide (CuS) nanocomposite was synthesized by hydrothermal method and used for the electrode modification with a N-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) as the substrate electrode. Hemoglobin (Hb) was immobilized on the modified electrode to get a biocompatible sensing platform. UV-vis absorption spectroscopic results confirmed that Hb retained its native secondary structure in the composite. Direct electron transfer of Hb incorporated into the nanocomposite was investigated with a pair of well-defined redox waves appeared on cyclic voltammogram, indicating the realization of direct electrochemistry of Hb on the modified electrode. The results can be ascribed to the presence of GR-CuS nanocomposite on the electrode surface that facilitates the electron transfer rate between the electroactive center of Hb and the electrode. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 3.0 to 64.0 mmol L(-1) with the detection limit of 0.20 mmol L(-1) (3σ). The fabricated biosensor displayed the advantages such as high sensitivity, good reproducibility and long-term stability.

Application of graphene-ionic liquid-chitosan composite-modified carbon molecular wire electrode for the sensitive determination of adenosine-5'-monophosphate.

In this paper, a graphene (GR) ionic liquid (IL) 1-octyl-3-methylimidazolium hexafluorophosphate and chitosan composite-modified carbon molecular wire electrode (CMWE) was fabricated by a drop-casting method and further applied to the sensitive electrochemical detection of adenosine-5'-monophosphate (AMP). CMWE was prepared with diphenylacetylene (DPA) as the modifier and the binder. The properties of modified electrode were examined by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical behaviors of AMP was carefully investigated with enhanced responses appeared, which was due to the presence of GR-IL composite on the electrode surface with excellent electrocatalytic ability. A well-defined oxidation peak of AMP appeared at 1.314 V and the electrochemical parameters were calculated by electrochemical methods. Under the selected conditions, the oxidation peak current of AMP was proportional to its concentration in the range from 0.01 µM to 80.0 µM with the detection limit as 3.42 nM (3σ) by differential pulse voltammetry. The proposed method exhibited good selectivity and was applied to the detection of vidarabine monophosphate injection samples with satisfactory results.

Molecular dynamics simulation of diffusion and structure of some n-alkanes in near critical and supercritical carbon dioxide at infinite dilution.

The diffusion coefficients of n-alkanes (from CH4 to C14H30) in near critical and supercritical carbon dioxide at infinite dilution have been studied by molecular dynamics simulation. The simulation results agree well with experiment, which suggests that the simulation method is a powerful tool to obtain diffusion coefficients of solutes in fluids at high pressures. The local structures of such fluids are further investigated by calculating radial distribution functions and coordination numbers. Meanwhile, the dihedral, end-to-end distance and radius of gyration, which are calculated to characterize the flexibility of n-alkanes, are used to reasonably explain the abnormal trends on radial distribution functions and coordination numbers. Moreover, it is found that the flexibility effects on diffusion in pure n-alkanes and infinitely dilute n-alkane/CO2 system are different. The differences in MD simulation results of molecular diffusion in such systems could be qualitatively explained by the flexibility.

Direct electrochemistry with enhanced electrocatalytic activity of hemoglobin in hybrid modified electrodes composed of graphene and multi-walled carbon nanotubes.

A graphene (GR) and multi-walled carbon nanotubes (MWCNT) hybrid was prepared and modified on a 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE). Hemoglobin (Hb) was immobilized on GR-MWCNT/CILE surface with Nafion as the film forming material and the modified electrode was denoted as Nafion/Hb-GR-MWCNT/CILE. Spectroscopic results revealed that Hb molecules retained its native structure in the GR-MWCNT hybird. Electrochemical behaviors of Hb were carefully investigated by cyclic voltammetry with a pair of well-defined redox peaks obtained, which indicated that direct electron transfer of Hb was realized in the hybrid modified electrode. The result could be attributed to the synergistic effects of GR-MWCNT hybrid with enlarged surface area and improved conductivity through the formation of a three-dimensional network. Electrochemical parameters of the immobilized Hb on the electrode surface were further calculated with the results of the electron transfer number (n) as 1.03, the charge transfer coefficient (a) as 0.58 and the electron-transfer rate constant (ks) as 0.97 s(-1). The Hb modified electrode showed good electrocatalytic ability toward the reduction of different substrates such as trichloroacetic acid in the concentration range from 0.05 to 38.0 mmol L(-1) with a detection limit of 0.0153 mmol L(-1) (3σ), H2O2 in the concentration range from 0.1 to 516.0 mmol L(-1) with a detection limit of 34.9 nmol/L (3σ) and NaNO2 in the concentration range from 0.5 to 650.0 mmol L(-1) with a detection limit of 0.282 µmol L(-1) (3σ). So the proposed electrode had the potential application in the third-generation electrochemical biosensors without mediator.

Fabrication of graphene-platinum nanocomposite for the direct electrochemistry and electrocatalysis of myoglobin.

In this paper a platinum (Pt) nanoparticle decorated graphene (GR) nanosheet was synthesized and used for the investigation on direct electrochemistry of myoglobin (Mb). By integrating GR-Pt nanocomposite with Mb on the surface of carbon ionic liquid electrode (CILE), a new electrochemical biosensor was fabricated. UV-Vis absorption and FT-IR spectra indicated that Mb remained its native structure in the nanocomposite film. Electrochemical behaviors of Nafion/Mb-GR-Pt/CILE were investigated with a pair of well-defined redox peak appeared, which indicated that direct electron transfer of Mb was realized on the underlying electrode with the usage of the GR-Pt nanocomposite. The fabricated electrode showed good electrocatalytic activity to the reduction of trichloroacetic acid in the linear range from 0.9 to 9.0 mmol/L with the detection limit as 0.32 mmol/L (3σ), which showed potential application for fabricating novel electrochemical biosensors and bioelectronic devices.

Simultaneous electrochemical determination of guanosine and adenosine with graphene-ZrO2 nanocomposite modified carbon ionic liquid electrode.

In this paper an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was fabricated and used as the basal electrode, which was further modified by graphene (GR) and ZrO2 nanoparticle with chitosan (CTS) film to immobilize the nanocomposite. The modified electrode was denoted as CTS-GR-ZrO2/CILE and further used for the simultaneous detection of adenosine and guanosine. Electrochemical performances of the modified electrode were greatly enhanced due to the presence of GR-ZrO2 nanocomposite, and the direct electro-oxidation behaviors of adenosine and guanosine were carefully investigated. Both adenosine and guanosine exhibited an increase of the oxidation peak currents with the negative shift of the oxidation peak potentials on the modified electrode, which indicated the electrocatalytic activity of GR-ZrO2 nanocomposite on the electrode surface. Electrochemical parameters of adenosine and guanosine on CTS-GR-ZrO2/CILE were calculated respectively, and a new electroanalytical method for the simultaneous determination of adenosine and guanosine was further established with the peak-to-peak separation (ΔEp) as 0.225V. The proposed method was successfully applied to detect adenosine and guanosine in human urine samples with satisfactory results.

MD simulation of self-diffusion and structure in some n-alkanes over a wide temperature range at high pressures.

Self-diffusion and structural properties of n-alkanes have been studied by molecular dynamics simulation in the temperature range between the melting pressure curve and 600 K at pressures up to 300 MPa. The simulated results of lower n-alkanes are in good agreement with the existing experimental data, and support the reliability of results of the simulations of self-diffusion coefficients obtained at the extreme conditions. We predict the self-diffusion coefficients for methane, ethane, propane and n-butane at the similar reduced temperatures and pressures to draw a comparison between them. Then the correlation between self-diffusion and structural properties are further investigated by calculating the coordination numbers. Moreover, we define four distances and their corresponding relative deviations to characterize the flexibility of long-chain n-alkanes. The simulated results show that the self-diffusion of n-alkane molecules is mainly affected by the close packing, and the flexibility has a strong impact on the self-diffusion of longer n-alkane molecules.

Direct electrochemistry of hemoglobin on graphene and titanium dioxide nanorods composite modified electrode and its electrocatalysis.

A biocompatible sensing platform based on graphene (GR) and titanium dioxide (TiO2) nanorods for the immobilization of hemoglobin (Hb) was adopted in this paper. The GR-TiO2-Hb composite-modified carbon ionic liquid electrode was constructed through a simple casting method with Nafion as the film forming material. UV-Vis and FT-IR spectra confirmed that Hb retained its native structure in the composite film. Direct electron transfer of Hb incorporated into the composite was realized with a pair of quasi-reversible redox waves appeared, indicating that the presence of GR-TiO2 nanocomposite on the electrode surface could facilitate the electron transfer rate between the electroactive center of Hb and the substrate electrode. Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid in the concentration range from 0.6 to 21.0 mmol L⁻¹. These results indicated that GR-TiO2 nanocomposite could be a friendly biocompatible interface for immobilizing biomolecules and keeping their native structure. The fabricated biosensor displayed the advantages such as high sensitivity, good reproducibility and long-term stability.

Electrochemical deoxyribonucleic acid biosensor based on carboxyl functionalized graphene oxide and poly-L-lysine modified electrode for the detection of tlh gene sequence related to vibrio parahaemolyticus.

A carboxyl functionalized graphene oxide (GO-COOH) and electropolymerized poly-l-lysine (PLLy) modified glassy carbon electrode (GCE) was fabricated and used for the construction of an electrochemical deoxyribonucleic acid (DNA) biosensor. The NH(2) modified probe ssDNA sequences were immobilized on the surface of GO-COOH/PLLy/GCE by covalent linking with the formation of amide bonds, which was stable and further hybridized with the target ssDNA sequence. Differential pulse voltammetry (DPV) was used to monitor the hybridization events with methylene blue as electrochemical indicator, which gave a sensitive reduction peak at -0.287 V (vs. SCE). Under the optimal conditions the reduction peak current was proportional to the concentration of tlh gene sequence in the range from 1.0×10(-12) to 1.0×10(-6) mol L(-1) with a detection limit as 1.69×10(-13) mol L(-1) (3σ). The polymerase chain reaction products of tlh gene from oyster samples were detected with satisfactory results, indicating the potential application of this electrochemical DNA sensor.

Poly(methylene blue) functionalized graphene modified carbon ionic liquid electrode for the electrochemical detection of dopamine.

An ionic liquid 1-butylpyridinium hexafluorophosphate based carbon ionic liquid electrode (CILE) was used as the substrate electrode and a poly(methylene blue) (PMB) functionalized graphene (GR) composite film was co-electrodeposited on CILE surface by cyclic voltammetry. The PMB-GR/CILE exhibited better electrochemical performances with higher conductivity and lower electron transfer resistance. Electrochemical behavior of dopamine (DA) was further investigated by cyclic voltammetry and a pair of well-defined redox peaks appeared with the peak-to-peak separation (ΔE(p)) as 0.058V in 0.1 mol L(-1) pH 6.0 phosphate buffer solution, which proved a fast quasi-reversible electron transfer process on the modified electrode. Electrochemical parameters of DA on PMB-GR/CILE were calculated with the electron transfer number as 1.83, the charge transfer coefficients as 0.70, the apparent heterogeneous electron transfer rate constant as 1.72 s(-1) and the diffusional coefficient (D) as 3.45×10(-4) cm(2) s(-1), respectively. Under the optimal conditions with differential pulse voltammetric measurement, the linear relationship between the oxidation peak current of DA and its concentration was obtained in the range from 0.02 to 800.0 µmol L(-1) with the detection limit as 5.6 nmol L(-1) (3σ). The coexisting substances exhibited no interference and PMB-GR/CILE was applied to the detection of DA injection samples and human urine samples with satisfactory results.

[The characterization on the site of vindoline binding to human serum albumin].

In this paper, the fluorogenic property of vindoline was exploited and, as a probe, used to analyze the interaction of vindoline with HSA by fluorescence and absorption spectra in combination with molecular modeling under a simulated physiological conditions. The evidences from synchronous fluorescence and absorption spectroscopes showed the effect of vindoline on the microenvironment around HSA in aqueous solution. Data obtained by the fluorescence spectroscopy indicated that binding of vindoline with HSA leads to dramatic enhancement of the fluorescence emission intensity. The binding constants and the number of binding sites between vindoline and HSA at different temperatures (303, 310 and 317 K) were calculated according to the data obtained from fluorescence titration. Molecular docking was performed to reveal the possible binding mode or mechanism and suggested that vindoline can bind strongly to HSA. It is considered that vindoline binds to HSA mainly by a hydrophobic interaction and there are four hydrogen bonds interactions between the drug and the residues Ala291, Arg222, Arg218 and Lys195, separately. Fluorescent displacement measurements confirmed that vindoline bind HSA on site II. The thermodynamic parameters obtained (the enthalpy change deltaH0 and the entropy change deltaS0 were calculated to be -10.30 kJ x mol(-1) and 79.98 J x mol(-1) x K(-1), respectively, according to the Van't Hoff equation) suggested that hydrophobic and electrostatic interaction is the predominant intermolecular forces stabilizing the complex.