Fibronectin displacement at polymer surfaces

The interactions of fibronectin with thin polymer films are studied in displacement experiments using human serum albumin. Fibronectin adsorption and exchange on two different maleic anhydride copolymer surfaces differing in hydrophobicity and surface charge density have been analyzed by quartz crystal microbalance and laser scanning microscopy with respect to adsorbed amounts, viscoelastic properties, and conformation. Fibronectin is concluded to become attached onto hydrophilic surfaces as a "softer", less rigid protein layer, in contrast to the more rigid, densely packed layer on hydrophobic surfaces. As a result, the fibronectin conformation is more distorted on the hydrophobic substrates together with remarkably different displacement characteristics in dependence on the adsorbed fibronectin surface concentration and the displacing albumin solution concentration. While the displacement kinetic remains constant for the strongly interacting surface, an acceleration in fibronectin exchange is observed for the weakly interacting surface with increasing fibronectin coverage. For displaced amounts, no change is determined for the hydrophobic substrate, in contrast to the hydrophilic substrate with a decrease of fibronectin exchange with decreasing coverage leading finally to a constant nondisplaceable amount of adsorbed proteins. Furthermore, the variation of the albumin exchange concentration reveals a stronger dependence of the kinetic for the weakly interacting substrate with higher rates at higher albumin concentrations.     

Synthese,Kristallstruktur und elektronische Bandstruktur der isotypen Sulfidchloride CuBiSCl2 und AgBiSCl2

Synthesis, Crystal Structure and Electronic Band Structure of the Isostructural Sulfide Chlorides CuBiSCl₂ and AgBiSCl₂ Black, platelet crystals of MBiSCl₂ (M = Cu, Ag) were synthesized by heating stoichiometric amounts of MCl and BiSCl. X‐ray diffraction on powders and single‐crystals revealed that the compounds crystallize isostructural with space group Cmcm (Cu/Ag: a = 396.9(1)/397.1(1); b = 1278.6(3)/1371.2(3); c = 859.7(2)/882.4(2) pm). In the crystal structures the Bi^III cations have a bi‐capped trigonal prismatic coordination of two sulfide and six chloride ions. The polyhedra constitute layers equation/tex2gif-stack-2.gif[BiS_2/2Cl_6/3^—] by sharing common edges and faces. The layers are separated by transition metal cations M^I. Their distorted octahedral coordination comprises two short bonds M—S in trans position and four M—Cl bonds that are about 50 pm longer. From relativistic band structure calculations (DFT) is deduced that AgBiSCl₂ is an indirect semi‐conductor with a band gap of about 1.0 eV.     

Novel starshaped initiators for the controlled radical polymerization based on resorcin[4]- and pyrogallol[4]arenes

Multifunctional macrocyclic initiators for the atom transfer radical polymerization (ATRP) based on different resorcin[4]- and pyrogallol[4]arenes have been synthesized. The initiators with 8, 12 and 16 tertiary -bromoesters on the core were received by complete esterification of all phenolic groups with 2-bromo-isobutyryl bromide. The calixarene derivatives with aliphatic chains on the bridging methine carbon were obtained as their rccc (all cis) isomers, while the corresponding calixarenes with aromatic substituents gave mixtures of their rccc and rctt (cis, cis, trans, trans) isomers.     

Anion Controlled Supramolecular Self‐Assembly of Tetraprotonated Tris[2‐(benzylamino)ethyl]amine

The novel supramolecular assembly of composition [{(bz₃tren)H₄}⁴⁺ · (ReO₄)^— · 3(Cl)^—] resulted from the self‐organization of a mixture of tris[2‐(benzylamino)ethyl]amine (bz₃tren), HCl and NH₄ReO₄ at a molar ratio of 1:4.7:1 in methanol. The crystal architecture is characterized by stacks of repeating sandwich‐type building blocks that contain charge‐assisted N—H···O(Re) hydrogen bonds [N···O 2.81‐2.86Å] and weaker C—H···O(Re) interactions [C···O 3.11Å]. The stacks are further linked by N—H···Cl [N···Cl 3.03Å] and weaker C—H···Cl [C···Cl 3.47‐3.74Å] interactions into two‐dimensional layers bordered by the benzyl groups of the [(bz₃tren)H₄]⁴⁺ cations. Edge‐to‐face C—H···π interactions involving the aromatic rings occur within and between the layers. The protonation constants of bz₃tren in methanol were determined by potentiometric titration. The corresponding structures of the ligand in its different protonation states were calculated at the DFT‐level.     

LaSeTe2-temperature dependent structure investigation and electron holography on a charge-density-wave-hosting compound

Single crystals of LaSeTe(2) have been prepared by reaction of the elements in a LiCl/RbCl flux at 970 K for seven days. Satellite reflections observed in diffraction experiments indicate the presence of an incommensurate lattice distortion, which is of the charge-density-wave (CDW) type. The modulated structure has been solved from X-ray data at 173, 293, and 373 K. LaSeTe(2) crystallizes in the 3+1-dimensional orthorhombic superspace group Cmcm(00gamma)s00 (No. 63.2) with lattice parameters of a=4.295(1), b=25.371(4), c=4.306(1) A (173 K), a=4.297(1), b=25.408(4), c=4.309(1) A (293 K), and a=4.309(1), b=25.481(6), c=4.321(1) A (373 K). The modulation vector q=(0, 0, 0.288) does not change over the temperature interval. Electron holographic investigations confirm the existence of the modulation and help to visualize the charge-density wave.     

In‐line Bragg magnifier based on V‐shaped germanium crystals

In this work an X‐ray imaging system based on a recently developed in‐line two‐dimensional Bragg magnifier composed of two monolithic V‐shaped crystals made of dislocation‐free germanium is presented. The channel‐cut crystals were used in one‐dimensional and in two‐dimensional (crossed) configurations in imaging applications and allowed measurement of phase‐contrast radiograms both in the edge‐enhanced and in the holographic regimes. The measurement of the phase gradient in two orthogonal directions is demonstrated. The effective pixel size attained was 0.17 µm in the one‐dimensional configuration and 0.5 µm in the two‐dimensional setting, offering a twofold improvement in spatial resolution over devices based on silicon. These results show the potential for applying Bragg magnifiers to imaging soft matter at high resolution with reduced dose owing to the higher efficiency of Ge compared with Si.     

A portable ultrahigh‐vacuum system for advanced synchrotron radiation studies of thin films and nanostructures: EuSi2 nano‐islands

A portable ultrahigh‐vacuum system optimized for in situ variable‐temperature X‐ray scattering and spectroscopy experiments at synchrotron radiation beamlines was constructed and brought into operation at the synchrotron radiation facility ANKA of the Karlsruhe Institute of Technology, Germany. Here the main features of the new instrument are described and its capabilities demonstrated. The surface morphology, structure and stoichiometry of EuSi₂ nano‐islands are determined by in situ grazing‐incidence small‐angle X‐ray scattering and X‐ray absorption spectroscopy. A size reduction of about a factor of two of the nano‐islands due to silicide decomposition and Eu desorption is observed after sample annealing at 1270 K for 30 min.