Protein-protein interactions in reversibly assembled nanopatterns

We describe herein a platform to study protein-protein interactions and to form functional protein complexes in nanoscopic surface domains. For this purpose, we employed multivalent chelator (MCh) templates, which were fabricated in a stepwise procedure combining dip-pen nanolithography (DPN) and molecular recognition-directed assembly. First, we demonstrated that an atomic force microscope (AFM) tip inked with an oligo(ethylene glycol) (OEG) disulfide compound bearing terminal biotin groups can be used to generate biotin patterns on gold achieving line widths below 100 nm, a generic platform for fabrication of functional nanostructures via the highly specific biotin-streptavidin recognition. Subsequently, we converted such biotin/streptavidin patterns into functional MCh patterns for reversible assembly of histidine-tagged (His-tagged) proteins via the attachment of a tris-nitriloacetic acid (trisNTA) biotin derivative. Fluorescence microscopy confirmed reversible immobilization of the receptor subunit ifnar2-His10 and its interaction with interferon-alpha2 labeled with fluorescent quantum dots in a 7 x 7 dot array consisting of trisNTA spots with a diameter of approximately 230 nm. Moreover, we carried out characterization of the specificity, stability, and reversibility as well as quantitative real-time analysis of protein-protein interactions at the fabricated nanopatterns by imaging surface plasmon resonance. Our work offers a route for construction and analysis of functional protein-based nanoarchitectures.     

大、小齿轮磨削加工的对比

前言为了既保证预留的机器空间所需的负荷量的要求,并且有效减少变速器的噪音,有必要对大多数齿轮的齿形进行淬火后的进一步精加工。由于所涉及的齿轮在主要特征方面有所区别,比如:模数、齿顶圆直径、齿数、齿宽及由此而产生的不同重量,决定了对所采用的工艺流程和进行淬火后精加工使     

Functional Polysaccharide Composite Nanoparticles from Cellulose Acetate and Potential Applications

An in situ technique for preparing composite nanoparticles from hydrophobic cellulose acetate and hydrophilic polysaccharides using nanoprecipitation is presented. This technique allows the nanoparticles’ surface properties to be tuned very specifically. Spherical, narrow‐size‐distributed composite nanoparticles of different size, charge, functionality, and increased stability can be generated by using hydroxyethyl cellulose, carboxymethyl cellulose, low molecular weight chitosan, and amino cellulose. The influence of the pH and hydrophilic polysaccharide content in the particle formation is shown. The pH‐ and ionic strength‐ effective zeta‐potential functions are evidence of the presence of functional polysaccharides at the nanoparticle surface. The in situ technique is compared with the adsorption of hydrophilic polysaccharides onto cellulose acetate nanoparticles in two steps. The great potential of in situ prepared composite nanoparticles in the pharmaceutical industry and bio‐ or food technology, as carriers of hydrophobic substances in aqueous media and for specific surface modifications, e.g., to selectively introduce strong antimicrobial properties, is illustrated.     

Biomechanical and densitometric bone properties after callus distraction in sheep

Assessment of biomechanical stability of diaphyseal bone lengthened by callus distraction is an unsolved problem. A middiaphyseal corticotomy was performed in the left tibia of 24 sheep. After 7 days, callus distraction was begun at a rate of 0.5 mm every 12 hours for 30 days using a standard unilateral fixator system. Animals were euthanized 4, 8, or 12 weeks after the end of distraction. The lengthened tibia and the contralateral control tibia from each animal were evaluated by radiographic, densitometric (dual energy xray absorptiometry, quantitative computed tomography), and biomechanical (axial compression testing, torsion testing to failure) methods. The bone mineral density and maximum torque for the lengthened tibia were significantly greater in the 8-week group than in the 4-week group. However, the values in the 12-week group were significantly smaller than in the 8-week group. In the lengthened tibias, there was a correlation between the maximum torque and the bone mineral density, and between the maximum torque and the bone density. Bone density measurements are useful prognosticators for the safe removal of external fixators after leg lengthening procedures. By using these methods, clinical fractures after leg lengthening could be avoided in the future.     

Immunological assessment of exposure to Echinococcus granulosus in a rural dog population in Uruguay

An ELISA was used to screen a dog population in Uruguay (Sarandi Del Yi, Durazno District) for the prevalence of specific serum antibodies (IgG, IgA and IgE) to Echinococcus granulosus. The sensitivity (61%) and specificity (97%) of the ELISA were determined using well-defined serum groups. A total of 408 dogs from Sarandi del Yi and environs were screened serologically, and 29.7% (8.6-13.8% for each antibody class) of dogs had positive levels of antibody to E. granulosus. This antibody prevalence (exposure) was significantly higher than the percentage of dogs found to be positive for E. granulosus worms by arecoline purgation (7.6%). This level of exposure to E. granulosus determined by ELISA is considered unacceptable from a public health perspective. Measures will now focus on obtaining data on the true prevalence of current infection in this dog population and on determining the transmission patterns of the disease in this endemic region.     

Beschreibung der Fließkurve auf der Basis phänomenologischer Ansätze am Beispiel eines Baustahls

Zur Beschreibung der Fließkurve des untersuchten Baustahls wurde ein allgemeines phänomenologisches Modell zur Entwicklung der Gesamtversetzungsdichte mit der plastischen Vergleichsdehnung herangezogen. Spezielle Formen dieser Evolutionsgleichung liefern bekannte empirische Fließgesetze. Unter Berücksichtigung der Randbedingungen bei der Herleitung dieser Gesetze sind deren Koeffizienten physikalisch plausibel zu interpretieren. Der gebräuchlichen Hollomon-Gleichung ähnliche Potenzfunktionen, die eine additive Konstante enthalten, sind auf der Basis dieser Modellvorstellung als Fließgesetze ohne Berücksichtigung von Erholungsprozessen zu verstehen. Die Güte der Approximation ist folglich stark von der Versuchstemperatur abhängig. Die Voce-Gleichung stellt die exakteste Beschreibung der Fließkurve des untersuchten Stahls dar. Aufgrund der Berücksichtigung von Erholungsvorgängen enthält die Voce-Gleichung, im Gegensatz zu den anderen Ansätzen, eine Grenz- oder Sättigungsspannung, deren Temperaturabhängigkeit unter Zugrundelegung eines thermisch aktivierten Versetzungsprozesses quantifiziert werden kann. Abweichungen am Beginn homogener plastischer Verformung sind auf die Wirkung eines zweiten Strukturparameters, der Dichte der beweglichen Versetzungen zurückzuführen. Mit Hilfe neuerer Modellvorstellungen kann dieser Bereich quantitativ beschrieben werden.