A Preparative Method for the Isolation of Calponin from Molluscan Catch Muscle

We describe the development of a preparative method to isolate molluscan catch muscle, calponin. This method is based on the ability of calponin to interact with actin in a temperature-dependent manner. After extracting thin filaments, as previously described, the extract was ultracentrifuged at 2 °C. While other surface proteins of thin filaments co-precipitated with actin, calponin, along with some minor contaminants, remained in the supernatant. Calponin was purified through cation-exchange chromatography. The yield of pure protein was four-fold higher than that achieved through high-temperature extraction. To evaluate functionally isolated proteins, we determined the effect of calponin on Mg²⁺-ATPase activity of hybrid and non-hybrid actomyosin. The degree of ATPase inhibition was consistent with previously published data but strongly dependent on the environmental conditions and source of actin and myosin used. Furthermore, at low concentrations, calponin could induce the ATPase activity of hybrid actomyosin. This result was consistent with data indicating that calponin can modulate actin conformation to increase the relative content of “switched on” actin monomers in thin filaments. We assume that calponin obtained by the isolation method proposed herein is a fully functional protein that can both inhibit and induce the ATPase activity.     

Mapping of Lattice Strain in 4H-SiC Crystals by Synchrotron Double-Crystal X-ray Topography

The presence of lattice strain in n-doped 4H-SiC substrate crystals grown by a physical vapor transport method can strongly influence the performance of related power devices that are fabricated on them. Information on the level and the variation of lattice strain in these wafer crystals is thus important. In this study, a non-destructive method is developed based on synchrotron double-crystal x-ray topography to map lattice strains in 4H-SiC wafers. Measurements are made on two 4H-SiC substrate crystals—one is an unprocessed commercial wafer while the other was subject to a post-growth high-temperature heat treatment. Maps of different strain components are generated from the equi-misorientation contour maps recorded using synchrotron monochromatic radiation. The technique is demonstrated to be a powerful tool in estimating strain fields in 4H-SiC crystals. Analysis of the strain maps also shows that the normal strain components vary much more significantly than do the shear/rotation components, indicating that lattice dilation/compression rather than lattice tilt is the major type of deformation caused by both the incorporation of nitrogen dopants and the nucleation of basal plane dislocations.     

The thermogenic center in social wasps

In the social wasps Vespa orientalis and Paravespula germanica (Hymenoptera, Vespinae), a thermogenic center has been found in the dorsal part of the first thoracic segment. The temperature in this region of the prothorax is higher by 6-9 degrees C than that at the tip of the abdomen, and this in actively flying hornets outside the nest (workers, males or queens) as well as in hornets inside the nest that attend to the brood in the combs. On viewing the region from the outside, one discerns a canal or rather a fissure in the cuticle, which commences at the center of the dorsal surface of the prothorax and extends till the mesothorax. Thus the length of this canal or fissure is approximately 5-7 mm and it is seen to contain numerous thin hairs whose shape varies from that of the hairs alongside the structure. Beneath the cuticle in this region there are dorsoventral as well as longitudinal muscles in abundance, much the same as the musculature in the remaining thoracic segments (i.e. the meso- and metathorax), which activate the two pairs of wings. The canal-bearing segment is of course devoid of wings, and its dorsoventral muscles are attached to the cuticle, which in this region resembles a bowl harboring several layers of epithelium that boasts numerous butterfly-shaped tracheal branches. Additionally there are layers that display lymph-filled spaces and also perforated layers and depressions, and beneath all these is a lace-like layer that also coats the cuticle's hollows. Underneath the cuticle proper, there are numerous large mitochondria and tracheae, which occupy a considerable part of the cuticular epithelium surface. These abundant mitochondria are, most probably, the main element of heat production in the thermogenic center.     

Influence of different SiC surface treatments performed prior to Ni ohmic contacts formation

This work is dealing with the influence of surface treatment on ohmic contacts to hexagonal N-type SiC with medium doping level. The contact materials were Ni and Ni₂Si. The structures had to be annealed at high temperatures in order to reach ohmic behavior. A number of surface treatment methods were tested: wet cleaning, plasma etching, intentional oxidation with etching, H₂ annealing and their combinations. After some types of cleaning, the SiC surface was immediately analysed using the XPS method. The results of the analyses showed that the composition of the surface was not much influenced by these treatments. At lower annealing temperatures (approx. up to 850 °C) the prepared contacts showed Schottky behavior with large scatter of parameters. After annealing at approx. 960 °C, where the onset of ohmic behavior is expected, the structures were truly ohmic and of good parameters. Cleaning methods had just a negligible influence on the electrical parameters of the ohmic contacts. An explanation for these observed facts is suggested: Although - already on the basis of the XPS results - we could speak about a negligible influence of the cleaning onto the contact parameters, there might come across also other mechanisms coming from interaction of contact materials with SiC, which caused similar behavior of ohmic contacts on differently treated surfaces.     

Silver Stars: Silver–Polymer Composite Stars: Synthesis and Applications (Adv. Funct. Mater. 9/2011)

Colloidal “silver stars” were synthesized upon poly(lactic‐co‐glycolic) acid nanosphere templates via a facile two‐step silver reduction method. Myriad dendrimer‐like Ag star morphologies were synthesized by varying the amount of poly(vinyl alcohol) and trisodium citrate used during silver reduction. Scanning electron microscopy studies revealed that star‐shaped silver–polymer composites possessing nanoscopic, fractal morphologies with diameters ranging from 500 nm to 7 μm were produced. These composites have broad applications from antibacterial agents to catalysis; two such applications were tested here. Surface‐enhanced Raman spectroscopy (SERS) studies showed multiple hot spots of SERS activity within a single star. Electrochemical catalysis experiments demonstrated the feasibility of using the silver stars instead of platinum for the oxygen reduction reaction in alkaline fuel cells.     

Application of entropy formulas in detection of denial‐of‐service attacks

The paper compares five entropy formulas (Shannon, Tsallis, Rényi, Bhatia‐Singh, and Ubriaco) and their application in the detection of distributed denial‐of‐service (DDoS) attacks. The Shannon formula has been used extensively for this purpose for more than a decade. The use of the Tsallis and Rényi formulas in this context has also been proposed. Bhatia‐Singh entropy is a novel information metric with promising results in initial applications in this area. Ubriaco proposed an entropy function based on the fractional calculus. In this paper, flow size distribution was used as the input for detection. The type of DDoS attack is SYN flood, and simulation was used to obtain the input dataset. The results show that the Rényi and Bhatia‐Singh detectors perform better than the rest. Rényi and Tsallis performed similarly with respect to the true positive rate, but Rényi had a much lower false positive rate. The Bhatia‐Singh detector had the best true positive rate but a higher false positive rate than Rényi. The Ubriaco detector performed similar to the Shannon detector. With respect to detection delay, Tsallis, Ubriaco, and Shannon produced similar results, with a slight advantage associated with the Ubriaco detector, while Rényi and Bhatia‐Singh had a larger detection delay than the former three.     

Multimodal Magneto‐Plasmonic Nanoclusters for Biomedical Applications

Multimodal nanostructures can help solve many problems in the biomedical field including sensitive molecular imaging, highly specific therapy, and early cancer detection. However, the synthesis of densely packed, multicomponent nanostructures with multimodal functionality represents a significant challenge. Here, a new type of hybrid magneto‐plasmonic nanoparticles is developed using an oil‐in‐water microemulsion method. The nanostructures are synthetized by self‐assembly of primary 6 nm iron oxide core‐gold shell particles resulting into densely packed spherical nanoclusters. The dense packing of primary particles does not change their superparamagnetic behavior; however, the close proximity of the constituent particles in the nanocluster leads to strong near‐infrared (NIR) plasmon resonances. The synthesis is optimized to eliminate nanocluster cytotoxicity. Immunotargeted nanoclusters are also developed using directional conjugation chemistry through the Fc antibody moiety, leaving the Fab antigen recognizing region available for targeting. Cancer cells labeled with immunotargeted nanoclusters produce a strong photoacoustic signal in the NIR that is optimum for tissue imaging. Furthermore, the labeled cells can be efficiently captured using an external magnetic field. The biocompatible magneto‐plasmonic nanoparticles can make a significant impact in development of point‐of‐care assays for detection of circulating tumor cells, as well as in cell therapy with magnetic cell guidance and imaging monitoring.     

Robust Single Molecule Magnet Monolayers on Graphene and Graphite with Magnetic Hysteresis up to 28 K

The chemical functionalization of fullerene single molecule magnet Tb₂@C₈₀(CH₂Ph) enables the facile preparation of robust monolayers on graphene and highly oriented pyrolytic graphite from solution without impairing their magnetic properties. Monolayers of endohedral fullerene functionalized with pyrene exhibit magnetic bistability up to a temperature of 28 K. The use of pyrene terminated linker molecules opens the way to devise integration of spin carrying units encapsulated by fullerene cages on graphitic substrates, be it single-molecule magnets or qubit candidates.     

The effect of ripening and storage conditions on the distribution of tyramine,putrescine and cadaverine in Edam-cheese

The aim of the work was to describe the development of selected biogenic amines (histamine, tyramine, putrescine and cadaverine) in 4 layers of Dutch-type cheese (Edam-cheese) depending on 3 ripening/storage regimes during a 98-day period. Biogenic amines were analysed by means of ion-exchange chromatography. A further goal was to identify microbial sources of biogenic amines in the material analysed. Phenotype characterization and repetitive sequence-based PCR fingerprinting were used to identify the isolated bacteria. The highest content of tyramine, putrescine and cadaverine was determined in cheeses stored in a ripening cellar at a temperature of 10 °C during the whole observation period. Lower biogenic amines content was determined in samples which were moved into a cold storage device (5 °C) after 38 days of storage in a ripening cellar (10 °C). The lowest concentrations of biogenic amines were detected in cheeses which were moved into a cold storage device (5 °C) after 23 days of storage in a ripening cellar (10 °C). During the 98-day period, histamine was not detected in any of the regimes. Within the cheeses analysed, non-starter lactic acid bacteria Lactobacillus curvatus, Lactobacillus casei/paracasei and Lactobacillus plantarum were detected as the main producers of the biogenic amines tested. In starter bacteria Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris the decarboxylase activity tested was not detected.     

Upregulation of Cathepsin X in Glioblastoma: Interplay with γ-Enolase and the Effects of Selective Cathepsin X Inhibitors

Glioblastoma (GBM) is the most common and deadly primary brain tumor in adults. Understanding GBM pathobiology and discovering novel therapeutic targets are critical to finding efficient treatments. Upregulation of the lysosomal cysteine carboxypeptidase cathepsin X has been linked to immune dysfunction and neurodegenerative diseases, but its role in cancer and particularly in GBM progression in patients is unknown. In this study, cathepsin X expression and activity were found to be upregulated in human GBM tissues compared to low-grade gliomas and nontumor brain tissues. Cathepsin X was localized in GBM cells as well as in tumor-associated macrophages and microglia. Subsequently, potent irreversible (AMS36) and reversible (Z7) selective cathepsin X inhibitors were tested in vitro. Selective cathepsin X inhibitors decreased the viability of patient-derived GBM cells as well as macrophages and microglia that were cultured in conditioned media of GBM cells. We next examined the expression pattern of neuron-specific enzyme γ-enolase, which is the target of cathepsin X. We found that there was a correlation between high proteolytic activity of cathepsin X and C-terminal cleavage of γ-enolase and that cathepsin X and γ-enolase were colocalized in GBM tissues, preferentially in GBM-associated macrophages and microglia. Taken together, our results on patient-derived material suggest that cathepsin X is involved in GBM progression and is a potential target for therapeutic approaches against GBM.