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.

Templateless, surfactantless, simple electrochemical route to rapid synthesis of diameter-controlled 3D flowerlike gold microstructure with "clean" surface

We report for the first time a simple low-cost electrochemical route to synthesis of diameter-controlled hierarchical flowerlike gold microstructures with "clean'' surfaces using gold nanoplates or nanopricks as building blocks without introducing any template or surfactant.

Simple and sensitive aptamer-based colorimetric sensing of protein using unmodified gold nanoparticle probes

We describe herein simple and sensitive aptamer-based colorimetric sensing of protein (alpha-thrombin in this work) using unmodified gold nanoparticle probes.

A simple route to incorporate redox mediator into carbon nanotubes/Nafion composite film and its application to determine NADH at low potential

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nation). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thioine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as -0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.

Calculation of the bulk modulus of simple and complex crystals with the chemical bond method

The relation between the lattice energies and the bulk moduli on binary inorganic crystals was studied, and the concept of lattice energy density is introduced. We find that the lattice energy densities are in good linear relation with the bulk moduli in the same type of crystals, the slopes of fitting lines for various types of crystals are related to the valence and coordination number of cations of crystals, and the empirical expression of calculated slope is obtained. From crystal structure, the calculated results are in very good agreement with the experimental values. At the same time, by means of the dielectric theory of the chemical bond and the calculating method of the lattice energy of complex crystals, the estimative method of the bulk modulus of complex crystals was established reasonably, and the calculated results are in very good agreement with the experimental values.

Deposition of GdVO4 : Eu3+ nanoparticles on silica nanospheres by a simple sol-gel method

The deposition and coating of GdVO4: Eu3+ nanoparticles on spherical silica was carried out using a simple sol - gel method at low temperature. The GdVO4: Eu3+-coated silica composites obtained were characterized by differential thermal analysis (DTA), thermogravimetric (TG) analysis, x-ray diffraction (XRD), Fourier-transform IR spectroscopy (FT-IR), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), photoluminescence spectra, and kinetic decay. It is found that the similar to 5 nm GdVO4: Eu3+ nanoparticles coating the silica spheres are crystal in the as-prepared samples and the crystallinity increases with increasing annealing temperature. The composites obtained are spherical in shape with an average size of 100 nm. The GdVO4: Eu3+ nanoparticles are linked with silica cores by a chemical bond. The photoluminescence spectra of the obtained GdVO4: Eu3+-coated silica composites are similar to those of the bulk GdVO4: Eu3+ phosphors. The strongest peak is near 617 nm, which indicates that Eu3+ is located in the low symmetry site with non-inversion centre.

A simple and effective route for the preparation of poly(vinylalcohol) (PVA) nanofibers containing gold nanoparticles by electrospinning method

Poly(vinyl alcohol) (PVA) nanofibers containing gold nanoparticles have been simply obtained by electrospinning a solution containing gold nanoparticles without the additional step of introducing other stabilizing agents. The optical property of gold nanoparticles in PVA aqueous solution was observed by UV-visible absorption spectra. Morphology of the Au/PVA nanofibers and distribution of the gold nanoparticles were characterized by transmission electron. microscopy (TEM). The structure transformation was characterized from PVA to PVA/Au composite by Fourier transform infrared spectroscopy (FTIR).