Simple one-step process for immobilization of biomolecules on polymer substrates based on surface-attached polymer networks

For the miniaturization of biological assays, especially for the fabrication of microarrays, immobilization of biomolecules at the surfaces of the chips is the decisive factor. Accordingly, a variety of binding techniques have been developed over the years to immobilize DNA or proteins onto such substrates. Most of them require rather complex fabrication processes and sophisticated surface chemistry. Here, a comparatively simple immobilization technique is presented, which is based on the local generation of small spots of surface attached polymer networks. Immobilization is achieved in a one-step procedure: probe molecules are mixed with a photoactive copolymer in aqueous buffer, spotted onto a solid support, and cross-linked as well as bound to the substrate during brief flood exposure to UV light. The described procedure permits spatially confined surface functionalization and allows reliable binding of biological species to conventional substrates such as glass microscope slides as well as various types of plastic substrates with comparable performance. The latter also permits immobilization on structured, thermoformed substrates resulting in an all-plastic biochip platform, which is simple and cheap and seems to be promising for a variety of microdiagnostic applications.     

Synthesis, structure, and properties of a T-shaped 14-electron stiboranyl-gold complex

A cyclic stiboranyl-gold complex (1) supported by two 1,8-naphthalenediyl linkers has been synthesized and structurally characterized. The gold atom of this complex adopts a T-shaped geometry and is separated from the antimony center by only 2.76 ?. Surprisingly, the trivalent gold atom of this complex is involved in an aurophilic interaction, a phenomenon typically only observed for monovalent gold complexes. This phenomenon indicates that the stiboranyl ligand possesses strong σ-donating properties making the trivalent gold atom of 1 electron rich. This view is supported by DFT calculations as well as Au L(3)- and Sb K-edge XANES spectra which reveal that 1 may also be described as an aurate-stibonium derivative. In agreement with this view, complex 1 shows no reactivity toward the halides Cl(-), Br(-), and I(-). It does, however, rapidly react with F(-) to form an unprecedented anionic aurate fluorostiborane complex ([2](-)) which has been isolated as the tetra-n-butylammonium salt. The increased coordination number of the antimony center in this anionic complex ([2](-)) does not notably affect the Au-Sb separation (2.77 ?) or the geometry at the gold atom which remains T-shaped.     

Exixtence of vertices of local connectivityk in digraphs of large outdegree

For every positive integerk, there is a positive integerf(k) such that every finite digraph of minimum outdegreef(k) contains verticesx, y joined byk openly disjoint paths.     

A model for phosphorus segregation at the silicon-silicon dioxide interface

A new model for phosphorus segregation at the Si-SiO₂ interface is derived and verified by experimental data. The model considers for the first time, a third phase, the interface layer itself, in addition to the Si and SiO₂ phases, and the dynamics of the three-phase system is described in terms of rate equations. In particular, the phosphorus compound formation in the interface layer (phosphorus pile-up), which renders the dopant electrically inactive to a large extent, is described as a competition of the dopant in silicon and in silicon dioxide in filling and depleting a constant density of interface traps. Our model allows an unambiguous correlation of the dopant concentration on both sides of the interface with the integral dose of the interface phosphorus pile-up. Experimental data for different phosphorus concentrations, different temperatures, and different oxidation ambients, including inert anneals, are fitted by a single curve.     

Unusual crystal structure of non-superconducting Y1Ba2Cu3O7−x films on buffered silicon substrates

Superconducting common c-axis oriented YBCO films as well as non-superconducting films epitaxially grown at significantly reduced substrate temperatures were deposited by laser ablation on CeO₂/YSZ buffered silicon substrates. The crystal structure of the non-superconducting films measured by XRD is collapsed from the original orthorhombic one, whereas the chemical composition detected using RBS and EDX remains identical. Especially the oxygen content in the non-superconducting material is as high as in the common 90 K superconductor. Thus, the change in the electrical behaviour is only due to a structural modification. The crystallographic model of a simple cubic YBCO perovskite unit cell does not represent completely our experimental results measured on the non-superconducting YBCO. A modified model based on detailed TEM and XRD measurements and known crystal defects of orthorhombic YBCO is proposed.     

Synthèse dc la pyrido[2,3-f] phtalazine et des diformyl-6,7; -4,6; -4,7; -2,4 quinoleines

This article describes the synthesis of a new heterocycle, pyrido[2,3,f]phtalazine and three new diformylquinolincs.     

Beitrag zur Berechnung in Querrichtung durchlaufender Plattenstreifen mit Hilfe Fourierscher Integrale

Zusammenfassung Die Beanspruchungen und Verformungen eines Plattenstreifens unter dem Angriff eines Randmomentes wurden untersucht. Das Randmoment wurde in ein Fourier-sches Integral entwickelt. Die gesuchten Größen ergeben sich als bestimmte Integrale, die numerisch ausgewertet werden. Insbesondere wurde die Neigung der Biegefläche am betrachteten Rand untersucht. Für eine gegebene Belastung, die ebenfalls in Fouriersche Integrale entwickelt wurde, wurde am betrachteten Rand die Neigung der Biegefläche bestimmt. Aus der Bedingung einer horizontalen Tangente der Biegefläche bei starrer Einspannung, bzw. der Stetigkeit der Biegefläche über der Auflagerlinie bei durchlaufenden Platten konnte durch Vergleich der Randneigungen das Einspann- bzw. Stützmoment ermittelt werden. Anhand von Beispielen wurden der Rechnungsgang erläutert und Ergebnisse gewonnen.     

Synthèse des pyrido[2,3-d] el [3,2-d] -s-triazolo[3,4-f] pyrimidines el de (pyrazolyl-1')-4 pyrido[2,3-d] et [3,2-d] pyrimidines

The synthesis of two new heterocycles is described: pyrido-[2,3-d]-.s-triazolo[ 3,4-f] pyrimidine and pyrido[3,2-d]-.s-triayzolo-[3,4-f] pyrimidine. 4-[I'-Pyrazolyl]pyrido[2,3-d]pyrimidines and 4-[1′-pyrazoly1] pyrido[ 3,2-d] pyrimidine are obtained by the action of 4-hydrazinopyrido[2,3-d]pyrimidine and 4-hydrazinopyrido-[3,2-d]pyrimidine with several β-diketones.