Fine Tuning of Vesicle Assembly and Properties Using Dual Hydrophilic Triblock Copolypeptides

The design, synthesis, and self‐assembly of the first dual hydrophilic triblock copolypeptide vesicles, ${\rm R}_{m}^{{\rm H}} {\rm E}_{n} {\rm L}_{o} $ and ${\rm K}_{m}^{{\rm P}} {\rm R}_{n}^{{\rm H}} {\rm L}_{o} $ , is reported. Variation of the two distinct hydrophilic domains is used to tune cellular interactions without disrupting the self‐assembled structure. The aqueous self‐assemblies of these triblock copolypeptides in water are characterized using microscopy and DLS. Cell culture studies are used to evaluate cytotoxicity as well as intracellular uptake of the vesicles. The ability of polypeptides to incorporate ordered chain conformations that direct self‐assembly, combined with the facile preparation of functional, multiblock copolypeptide sequences of defined lengths, allow the design of vesicles attractive for development as drug carriers.

     

M?ssbauer study of the '11' iron-based superconductors parent compound Fe(1+x)Te

(57)Fe M?ssbauer spectroscopy was applied to investigate the superconductor parent compound Fe(1+x)Te for x?=?0.06, 0.10, 0.14, 0.18 within the temperature range 4.2-300?K. A spin density wave (SDW) within the iron atoms occupying regular tetrahedral sites was observed, with the square root of the mean square amplitude at 4.2?K varying between 9.7 and 15.7?T with increasing x. Three additional magnetic spectral components appeared due to the interstitial iron distributed over available sites between the Fe-Te layers. The excess iron showed hyperfine fields at approximately 16, 21 and 49?T for three respective components at 4.2?K. The component with a large field of 49?T indicated the presence of isolated iron atoms with large localized magnetic moments in interstitial positions. Magnetic ordering of the interstitial iron disappeared in accordance with the fallout of the SDW with increasing temperature.     

A unifying motif of intermolecular cooperativity in protein associations

At the molecular level, most biological processes entail protein associations which in turn rely on a small fraction of interfacial residues called hot spots. Our theoretical analysis shows that hot spots share a unifying molecular attribute: they provide a third-body contribution to intermolecular cooperativity. Such motif, based on the wrapping of interfacial electrostatic interactions, is essential to maintain the integrity of the interface. Thus, our main result is to unravel the molecular nature of the protein association problem by revealing its underlying physics and thus by casting it in simple physical grounds. Such knowledge could then be exploited in rational drug design since the regions here indicated may serve as blueprints to engineer small molecules disruptive of protein-protein interfaces.     

Exposure assessment and engineering control strategies for airborne nanoparticles: an application to emissions from nanocomposite compounding processes

In this study, nanoalumina and nanoclay particles were compounded separately with ethylene vinyl acetate (EVA) polymer to produce nanocomposites using a twin-screw extruder to investigate exposure and effective controls. Nanoparticle exposures from compounding processes were elevated under some circumstances and were affected by many factors including inadequate ventilation, surrounding air flow, feeder type, feeding method, and nanoparticle type. Engineering controls such as improved ventilation and enclosure of releasing sources were applied to the process equipment to evaluate the effectiveness of control. The nanoparticle loading device was modified by installing a ventilated enclosure surrounding the loading chamber. Exposures were studied using designed controls for comparison which include three scenarios: (1) no isolation; (2) enclosed sources; and (3) enclosed sources and improved ventilation. Particle number concentrations for diameters from 5 to 20,000 nm measured by the Fast Mobility Particle Sizer and aerodynamic particle sizer were studied. Aerosol particles were sampled on transmission electron microscope grids to characterize particle composition and morphology. Measurements and samples were taken at the near- and far-field areas relative to releasing sources. Airborne particle concentrations were reduced significantly when using the feeder enclosure, and the concentrations were below the baseline when two sources were enclosed, and the ventilation was improved when using either nanoalumina or nanoclay as fillers.     

An h-adaptive solution of the spherical blast wave problem

Shock waves and contact discontinuities usually appear in compressible flows, requiring a fine mesh in order to achieve an acceptable accuracy of the numerical solution. The usage of a mesh adaptation strategy is convenient as uniform refinement of the whole mesh becomes prohibitive in three-dimensional (3D) problems. An unsteady h-adaptive strategy for unstructured finite element meshes is introduced. Non-conformity of the refined mesh and a bounded decrease in the geometrical quality of the elements are some features of the refinement algorithm. A 3D extension of the well-known refinement constraint for 2D meshes is used to enforce a smooth size transition among neighbour elements with different levels of refinement. A density-based gradient indicator is used to track discontinuities. The solution procedure is partially parallelised, i.e. the inviscid flow equations are solved in parallel with a finite element SUPG formulation with shock capturing terms while the adaptation of the mesh is sequentially performed. Results are presented for a spherical blast wave driven by a point-like explosion with an initial pressure jump of 10⁵ atmospheres. The adapted solution is compared to that computed on a fixed mesh. Also, the results provided by the theory of self-similar solutions are considered for the analysis. In this particular problem, adapting the mesh to the solution accounts for approximately 4% of the total simulation time and the refinement algorithm scales almost linearly with the size of the problem.     

Effect of catalyst preparation on the yield of carbon nanotube growth

Multi-wall carbon nanotubes (MWCNTs) were synthesized by catalytic chemical vapor deposition (CVD) on catalytic iron nanoparticles dispersed in a silica matrix, prepared by sol gel method. In this contribution, variation of gelation condition on catalyst structure and its influence on the yield of carbon nanotubes growth was studied. The precursor utilized were tetraethyl-orthosilicate and iron nitrate. The sols were dried at two different temperatures in air (25 or 80 °C) and then treated at 450 °C for 10 h. The xerogels were introduced into the chamber and reduced in a hydrogen/nitrogen (10%v/v) atmosphere at 600 °C. MWCNTs were formed by deposition of carbon atoms from decomposition of acetylene at 700 °C. The system gelled at RT shows a yield of 100% respect to initial catalyst mass whereas the yield of that gelled at 80 °C was lower than 10%. Different crystalline phases are observed for both catalysts in each step of the process. Moreover, TPR analysis shows that iron oxide can be efficiently reduced to metallic iron only in the system gelled at room temperature. Carbon nanotubes display a diameter of about 25–40 nm and several micron lengths. The growth mechanism of MWCNTs is base growth mode for both catalysts.     

Scaling law and critical exponent for α0 at the 3D Anderson transition

We use high‐precision, large system‐size wave function data to analyse the scaling properties of the multifractal spectra around the disorder‐induced three‐dimensional Anderson transition in order to extract the critical exponents of the transition. Using a previously suggested scaling law, we find that the critical exponent ν is significantly larger than suggested by previous results. We speculate that this discrepancy is due to the use of an oversimplified scaling relation.     

1/fα fractal noise generation from Grünwald–Letnikov formula

This communication presents a recursive algorithm for generating streams of 1/f^α fractal noise, by means of fractional integration/differentiation of a white noise signal. The quality of correlated and anticorrelated noise obtained by this approach is evaluated by applying detrended fluctuation analysis.     

A novel alkenyl-substituted ansa-zirconocene complex with dual application as olefin polymerization catalyst and anticancer drug

The alkenyl substituted fulvene compound, (C₅H₄)CMe(CH₂CH₂CHCMe₂) (1), reacts with one equivalent of LiMe to give the lithium derivative Li{C₅H₄(CMe₂CH₂CH₂CHCMe₂)} (2). The reaction of 2 with Me₂Si(C₅Me₄H)Cl gave the ansa-ligand precursor Me₂Si(C₅Me₄H)(C₅H₄(CMe₂CH₂CH₂CHCMe₂)) (3), which after the subsequent reaction with 2 equivalents of LiBuⁿ yielded the dilithium salt Li₂{Me₂Si(C₅Me₄)(C₅H₃(CMe₂CH₂CH₂CHCMe₂))} (4). The alkenyl-substituted zirconocene complex [Zr{Me₂Si(η⁵-C₅Me₄)(η⁵-C₅H₃(CMe₂CH₂CH₂CHCMe₂))}Cl₂] (5) was synthesized by the equimolar reaction of 4 and ZrCl₄. 5 was characterized by spectroscopic methods and by single crystal X-ray diffraction studies. The zirconocene compound 5 has been tested as a catalyst in the polymerization of ethylene at different temperatures and Al:Zr ratios, and also in the co-polymerization of ethylene and 1-octene, observing modest co-monomer incorporations. In addition, the cytotoxic activity of 5 was tested against tumour cell lines 8505C anaplastic thyroid cancer, A253 head and neck tumour, A549 lung carcinoma, A2780 ovarian cancer and DLD-1 colon carcinoma. Complex 5 showed the best cytotoxic activity on A2780 ovarian cancer (IC₅₀ value of 36.8 ± 5.9 μM). This represents the highest reported cytotoxic activity of a zirconocene complex on A2780 ovarian cancer. In addition, the cytotoxic activities of 5, have been compared with those obtained using cisplatin.