Capillary electrophoretic analysis of mu- and m-calpain using fluorescently labeled casein substrates

Calpains are unique calcium-dependent thiol proteases that have been proposed to participate in a number of physiological processes including signal transduction and protein turnover in skeletal muscle. Calpains exist in two major forms. Interestingly, the two forms of protease show no significant difference in their action on various substrates. The only demonstrable difference in their activity involves the concentration of calcium required for activation. Both mu- and m-calpains typically achieve half maximal activation at 50 microM and 0.7 mM calcium, respectively. The focus of this study was to examine the action of both forms of calpain on casein substrates and assess whether any differences could be observed in the resulting peptide finger print using capillary electrophoresis. Purified mu- and m-calpain were incubated for various lengths of time with Oregon Green labeled alphas- and beta-casein. The reactions were stopped with sodium dodecyl sulfate (SDS) and products separated by capillary electrophoresis in micellar electrokinetic capillary chromatography (MEKC) mode using laser-induced fluorescence (LIF) detection. Comparison of the electropherograms showed no difference in the peptide profile for either enzyme. However, it was found that beta-casein was hydrolyzed more extensively than alphas-casein, by both enzymes. Capillary electrophoresis was found to be a very sensitive technique for detection of calpain activity. Using beta-casein as substrate, the CE approach was able to detect 2-3 ng of calpain activity. The results also suggest that capillary electrophoresis is a useful tool for proteolytic investigations of protein structure.     

Chromatographic analysis of methylmercaptopurine riboside in human plasma and urine.

An isocratic reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of methylmercaptopurine riboside (MMPR) in human plasma and urine is reported. Plasma samples were prepared for analysis by addition of internal standard (6-dimethylaminopurine 9-riboside) followed by extraction using disposable C18 cartridges. Urine samples were filtered through a 0.22-micron membrane prior to HPLC separation. The column effluent was monitored at 289 nm and quantitation performed using peak heights. The linear range for MMPR determination was from 10 to 500 ng/ml in plasma and from 0.25 to 50 micrograms/ml in urine. The reported method is convenient, sensitive, and reproducible, illustrating its usefulness for application in pharmacokinetic studies.     

The Origin of Shape Sensitivity in Palladium‐Catalyzed Suzuki–Miyaura Cross Coupling Reactions

The shape sensitivity of Pd catalysts in Suzuki–Miyaura coupling reactions is studied using nanocrystals enclosed by well‐defined surface facets. The catalytic performance of Pd nanocrystals with cubic, cuboctahedral and octahedral morphologies are compared. Superior catalytic reactivity is observed for Pd NCs with {100} surface facets compared to {111} facets. The origin of the enhanced reactivity associated with a cubic morphology is related to the leaching susceptibility of the nanocrystals. Molecular oxygen plays a key role in facilitating the leaching of Pd atoms from the surface of the nanocrystals. The interaction of O₂ with Pd is itself facet‐dependent, which in turn gives rise to more efficient leaching from {100} facets, compared to {111} facets under the reaction conditions.     

Additive manufacturing for energy storage: Methods,designs and material selection for customizable 3D printed batteries and supercapacitors

Additive manufacturing and 3D printing in particular have the potential to revolutionize existing fabrication processes, where objects with complex structures and shapes can be built with multifunctional material systems. For electrochemical energy storage devices such as batteries and supercapacitors, 3D printing methods allows alternative form factors to be conceived based on the end use application need in mind at the design stage. Additively manufactured energy storage devices require active materials and composites that are printable, and this is influenced by performance requirements and the basic electrochemistry. The interplay between electrochemical response, stability, material type, object complexity and end use application are key to realising 3D printing for electrochemical energy storage. Here, we summarise recent advances and highlight the important role of methods, designs and material selection for energy storage devices made by 3D printing, which is general to the majority of methods in use currently.     

Light-emitting diodes with semiconductor nanocrystals

Colloidal semiconductor nanocrystals are promising luminophores for creating a new generation of electroluminescence devices. Research on semiconductor nanocrystal based light-emitting diodes (LEDs) has made remarkable advances in just one decade: the external quantum efficiency has improved by over two orders of magnitude and highly saturated color emission is now the norm. Although the device efficiencies are still more than an order of magnitude lower than those of the purely organic LEDs there are potential advantages associated with nanocrystal-based devices, such as a spectrally pure emission color, which will certainly merit future research. Further developments of nanocrystal-based LEDs will be improving material stability, understanding and controlling chemical and physical phenomena at the interfaces, and optimizing charge injection and charge transport.     

High-performance liquid chromatographic determination of ethacrynic acid in human plasma.

A high-performance liquid chromatographic method for the determination of ethacrynic acid (EA) in human plasma is described. Plasma was prepared for analysis by addition of 4-(2,4-dichlorophenoxy)-butyric acid as an internal standard followed by acidification with hydrochloric acid and extraction with ethyl acetate. Separation was by isocratic reversed-phase chromatography, the column effluent was monitored at 280 nm and quantitation was performed using peak-area ratios. The linear range for EA determination was from 0.5 to 25 micrograms/ml with a lower limit of detection of 0.1 microgram/ml. The reported method is convenient, sensitive and reproducible, illustrating its usefulness for pharmacokinetic studies.     

Architected porous metals in electrochemical energy storage

Porous metallic structures are regularly used in electrochemical energy storage (EES) devices as supports, current collectors, or active electrode materials. Bulk metal porosification, dealloying, welding, or chemical synthesis routes involving crystal growth or self-assembly, for example, can sometimes provide limited control of porous length scale, ordering, periodicity, reproducibility, porosity, and surface area. Additive manufacturing has shown the potential to revolutionize the fabrication of architected metals, allowing complex geometries not usually possible by traditional methods, by enabling complete design freedom of a porous metal based on the required physical or chemical property to be exploited. We discuss properties of porous metal structures in EES devices and provide some opinions on how architected metals may alleviate issues with electrochemically active porous metal current collectors, and provide opportunities for optimum design based on electrochemical characteristics required by batteries, supercapacitors or other electrochemical devices.     

Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800 °C of new molecular precursors gives individual single-crystal nanoparticles of SiP(2)O(7), TiO(2), P(4)O(7,) WP(2)O(7) and SiO(2), depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2-6 nm for all products. While all nanoparticles are new by this method, WP(2)O(7) and SiP(2)O(7) nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP(2)O(7) was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO(2) and P(4)O(7). The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P(4)O(7) affects the nanocrystalline products: nanoparticles are observed for WP(2)O(7), with coalescing crystallization occurring for the amorphous host in which SiP(2)O(7) crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium-ion cathode materials, catalysis and nanocrystal embedded dielectric layers.