Evaluation of flavonoids binding to DNA duplexes by electrospray ionization mass spectrometry

In this study, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding interactions of ten flavonoid aglycones and ten flavonoid glycosides with DNA duplexes. Relative binding affinities of the flavonoids toward DNA duplexes were estimated based on the fraction of bound DNA. The results revealed that the 4'-OH group of flavonoid aglycones was essential for their DNA-binding properties. Flavonoid glycosides with sugar chain linked on ring A or ring B showed enhanced binding toward the duplexes over their aglycone counterparts, whereas glycosylation of the flavonol quercetin on ring C exhibited a less pronounced effect.

Chiral metallo-supramolecular complexes selectively recognize human telomeric G-quadruplex DNA

Here, we report the first example that one enantiomer of a supramolecular cylinder can selectively stabilize human telomeric G-quadruplex DNA. The P-enantiomer of this cylinder has a strong preference for G-quadruplex over duplex DNA and, in the presence of sodium, can convert G-quadruplexes from an antiparallel to a hybrid structure. The compound's chiral selectivity and its ability to discriminate quadruplex DNA have been studied by DNA melting, circular dichroism, gel electrophoresis, fluorescence spectroscopy and S1 nuclease cleavage.

Electrochemical corrosion behavior of Mg-5Al-0.4Mn-xNd in NaCl solution

The electrochemical corrosion behavior of Mg-5Al-0.4Mn-xNd (x = 0, 1, 2 and 4 wt.%) alloys in 3.5% NaCl solution was investigated. The corrosion behavior of the alloys was assessed by open circuit potential measure, potentiodynamic polarization, and electrochemical impedance spectroscopy. The electrochemical results show the intermetallic precipitates with Nd behave as less noble cathodes in micro-galvanic corrosion and suppress the cathodic process. During corrosion, Al2O3 and Nd2O3, in proper ratio, is incorporated into the corrosion film, and enhances the corrosion resistance.

Electrolytic Deposition and Diffusion of Lithium onto Magnesium-9 Wt Pct Yttrium Bulk Alloy in Low-Temperature Molten Salt of Lithium Chloride and Potassium Chloride

The electrolytic deposition and diffusion of lithium onto bulk magnesium-9 wt pct yttrium alloy cathode in molten salt of 47 wt pct lithium chloride and 53 wt pct potassium chloride at 693 K were investigated. Results show that magnesium-yttrium-lithium ternary alloys are formed on the surface of the cathodes, and a penetration depth of 642 mu m is acquired after 2 hours of electrolysis at the cathodic current density of 0.06 A center dot cm(-2). The diffusion of lithium results in a great amount of precipitates in the lithium containing layer. These precipitates are the compound of Mg41Y5, which arrange along the grain boundaries and hinder the diffusion of lithium, and solid solution of yttrium in magnesium. The grain boundaries and the twins of the magnesium-9 wt pct yttrium substrate also have negative effects on the diffusion of lithium.

Stabilization of Imidosamarium(III) Cubane by Amidinates

An imidosamarium(III) cubane has been prepared from the reductive cleavage of azobenzene by a divalent samarium bis (amidinate) complex, indicating that the "spectratoe" bis(amidinate) and the resulting imido ligands help to stabilize the cubane framework. The cubane-type imido cluster is a novel unit in lanthanide chemistry.

Progress in Ru (bpy)(3)(2+) Electrogenerated Chemiluminescence

Among various ECL systems, such as 9,10-diphenylanthracene, lucigenin, tris(2,2'-bipyridyl) ruthenium, peroxyoxalate, luminol, graphene, and nanocrystals, Ru(bpy)(3)(2+) ECL is one of the most widely studied ECL systems in recent years due to its broad applications in immunoassays, DNA probe assays, coreactants analysis, and aptasensors. In this review, the progress in Ru(bpy)(3)(2+) ECL has been summarized on the whole, and the future research trends have been proposed.

Direct electrochemistry of glucose oxidase and biosensing for glucose based on carbon nanotubes@SnO2-Au composite

Multiwalled carbon nanotubes@SnO2-Au (MWCNTs@SnO2-Au) composite was synthesized by a chemical route. The structure and composition of the MWCNTs@SnO2-Au composite were confirmed by means of transmission electron microscopy, X-ray photoelectron and Raman spectroscopy. Due to the good electrocatalytic property of MWCNTs@SnO2-Au composite, a glucose biosensor was constructed by absorbing glucose oxidase (GOD) on the hybrid material. A direct electron transfer process is observed at the MWCNTs@SnO2-Au/GOD-modified glassy carbon electrode. The glucose biosensor has a linear range from 4.0 to 24.0 mM, which is suitable for glucose determination by real samples. It should be worthwhile noting that, from 4.0 to 12.0 mM, the cathodic peak currents of the biosensor decrease linearly with increasing the glucose concentrations in human blood. Meanwhile, the resulting biosensor can also prevent the effects of interfering species.

Highly ordered mesoporous carbons-based glucose/O-2 biofuel cell

This study demonstrates a novel compartment-less glucose/O-2 biofuel cell (BFC) based on highly ordered mesoporous carbons (OMCs) with three-dimensionally (3D) interconnected and ordered pore structures. OMCs are used as supports for both stably confining the electrocatalyst (i.e., meldola's blue, MDB) for NADH oxidation and the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose oxidation, and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., laccase, LAC) for O-2 electroreduction. In 0.10 M pH 6.0 PBS containing 20 mM NAD(+) and 60 mM glucose under the air-saturated atmosphere, the open circuit voltage (0.82 V) and the maximum power output (38.7 mu W cm(-2) (at 0.54V)) of the assembled compartment-less OMCs-based BFC are both higher than those of carbon nanotubes (CNTs)-based BFC (0.75 V and 2.1 mu W cm(-2) (at 0.46 V)).

Antioxidant Sensors Based on Iron Diethylenetriaminepentaacetic Acid, Hematin, and Hemoglobin Modified TiO2 Nanoparticle Printed Electrodes

Antioxidant amperometric sensors based on iron-containing complexes and protein modified electrodes were developed. Indium tin oxide glass was printed with TiO2 nanoparticles, onto which iron-containing compounds and protein were adsorbed. When applied with negative potentials, the dissolved oxygen is reduced to H2O2 at the electrode surface, and the H2O2 generated in situ oxidizes Fe-II to Fe-III, and then electrochemical reduction of Fe-III therefore gives rise to a catalytic current. In the presence of antioxidants, H2O2 was scavenged, the catalytic current was reduced, and the decreased current signal was proportional to the quantity of existing antioxidants. A kinetic model was proposed to quantify the H2O2 scavenging capacities of the antioxidants. With the use of the sensor developed here, antioxidant measurements can be done quite simply: put the sensor into the sample solutions (in aerobic atmosphere), perform a cathodic polarization scan, and then read the antioxidant activity values. The present work can be complementary to the previous studies of antioxidant sensor techniques based on OH radicals and superoxide ions scavenging methods, but the sensor developed here is much easier to fabricate and use.

A Simple, Universal Colorimetric Assay for Endonuclease/Methyltransferase Activity and Inhibition Based on an Enzyme-Responsive Nanoparticle System

An enzyme responsive nanoparticle system that uses a DNA-gold nanoparticle (AuNP) assembly as the substrate has been developed for the simple, sensitive, and universal monitoring of restriction endonucleases in real time. This new assay takes advantage of the palindromic recognition sequence of the restriction nucleases and the unique optical properties of AuNPs and is simpler than the procedure previously described by by Xu et al. (Angew. Chem. Int. Ed. Engl. 2007, 46, 3468-3470). Because it involves only one type of ssDNA modified AuNPs, this assay can be directed toward most of the endonucleases by simply changing the recognition sequence found within the linker DNA. In addition, the endonuclease activity could be quantitatively analyzed by the value of the reciprocal of hydrolysis half time (t(1/2)(-1). Furthermore, our new design could also be applied to the assay of methyltransferase activity since the methylation of DNA inhibits its cleavage by the corresponding restriction endonuclease, and thus, this new methodology can be easily adapted to high-throughput screening of methyltransferase inhibitors.

Enhanced catalytic DNAzyme for label-free colorimetric detection of DNA

A DNAzyme-based label-free method for the colorimetric detection of DNA is introduced, with a supramolecular hemin G-quartet complex as the sensing element and a 36-mer single-strand DNA as the analyte that is detected at 10 nM.

Characterization of procaine metabolism as probe for the butyrylcholinesterase enzyme investigation by simultaneous determination of procaine and its metabolite using capillary electrophoresis with electrochemiluminescence detection

Capillary electrophoresis with electrochemiluminescene detection was used to characterize procaine hydrolysis as a probe for butyrylcholinesterase by in vitro procaine metabolism in plasma with butyrylcholinesterase acting as bioscavenger. Procaine and its metabolite N,N-diethylethanolamine were separated at 16 kV and then detected at 1.25 V in the presence of 5.0 mM Ru(bpy)(3)(2+), with the detection limits of 2.4 x 10(-7) and 2.0 x 10(-8) mol/L (S/N=3), respectively. The Michaelis constant K-m value was 1.73 x 10(-4) mol/L and the maximum velocity V-max was 1.62 x 10(-6) mol/L/min. Acetylcholine bromide and choline chloride presented inhibition effects on the enzymatic cleavage of procaine, with the 50% inhibition concentration (IC50) of 6.24 x 10(-3) and 2.94 x 10(-4) mol/L.

Effective enhancement of peroxydisulfate electrochemiluminescence on C-60/DDAB films

Effective enhancement of electrochermluminescence (ECL) of peroxydisulfate on a C-60/didodecyldimethyl ammonium bromide (C-60/DDAB) film coated glassy carbon electrode (GCE) surface is reported in this paper. The C60/DDAB film gave lower cathodic current in the presence of peroxydisulfate than that from a bare GCE. To our surprise, electrochemiluminescent intensity from peroxydisulfate reduction was effectively enhanced on the C60/DDAB film, which was 50 times and 250 times higher than those from a DDAB film coated and bare GCE, respectively. Moreover, the ECL onset potential on the C60/DDAB film was about -0.9 V, which positively shifted 200 mV compared with that from the bare GCE. Dissolved oxygen and the applied potential also affected the electrochemiluminescent intensity. The presence of oxygen decreased the intensity, and the intensity reached maximum at the applied potential of -1.7 V. The unique property will greatly enrich ECL studies and applications based on fullerenes.

A biofuel cell harvesting energy from glucose-air and fruit juice-air

The membraneless biofuel cell (BFC) is facile prepared based on glucose oxidase and laccase as anodic and cathodic catalyst, respectively, by using 1,1'-dicarboxyferrocene as the mediators of both anode and cathode. The BFC can work by taking glucose as fuel in air-saturated solution, in which air serves as the oxidizer of the cathode. More interestingly, the fruit juice containing glucose, e.g. grape, banana or orange juice as the fuels substituting for glucose can make the BFC work. The BFC shows several advantages which have not been reported to our knowledge: (1) it is membraneless BFC which can work with same mediator on both anode and cathode; (2) fruit juice can act as fuels of BFCs substituting for usually used glucose; (3) especially, the orange juice can greatly enhance the power output rather than that of glucose, grape or banana juice. Besides, the facile and simple preparation procedure and easy accessibility of fruit juice as well as air being whenever and everywhere imply that our system has promising potential for the development and practical application of BFCs.