Gold layers on untreated and plasma-treated substrates of quaternized polysulfones

Thin gold layers were sputtered on the quaternized polysulfones (containing different tertiary amines—N,N-dimethylethylamine and N,N-dimethyloctylamine, respectively) surfaces unmodified and modified by low-pressure and high-frequency plasma treatment. Adhesion and morphological aspects of complex structures were studied for different gold sputtering and plasma treatment times. Water contact angle, atomic force microscopy, and surface properties reveal that adhesion increases with gold sputtering and plasma treatment times. Values of the mean adhesion force between cantilever and the studied surfaces, measured from AFM investigation, were correlated with quaternized polysulfone structures, modification of hydrophobicity after plasma treatment, and gold deposition on polymer surfaces.     

Hard porous chromium containing macrospheres as new catalysts for the esterification reaction of acetic acid with epichlorohydrin

This paper reports a systematic study on the preparation, characterization and testing of metallosilicate macrobeads that contain chromium ions as active catalytic centers. In order to obtain hard macrospheres, four metals (Cr, Al, Zr and Zn) were incorporated into the silica matrix using chitosan as a template and shape generator. Metallosilicate macrospheres were synthesized at room temperature using tetraethylorthosilicate as silicon source and chlorohydric acid as catalyst. The size of metallosilicate macrospheres was in the range 0.9 — 1.1 mm. The catalyst was characterised by means of water sorption technique, FTIR spectroscopy and SEM/EDX analyses. FTIR spectra put into evidence the presence of metallic ions within the silica framework. EDX analyses confirmed the efficient incorporation of metals within the silica matrix (the content of metals from the calcined catalyst is almost the same as that from the initial gel mixture). Porous structure of catalyst investigated by water sorption technique and by pycnometric methods (with n-heptan and mercury respectively) proved that the synthesized catalyst had micro, meso and macropores. Catalyst was tested in the esterification reaction of acetic acid with epichlorohydrin. The temperature and the amount of catalyst exerted a marked influence on reaction rate. This work opens new perspectives for heterogeneous catalysis encouraging the replacement of powder catalysts with macrospherical catalysts that are easy to recover and to reuse.      

Regioselective Synthesis of Polyheterohalogenated Naphthalenes via the Benzannulation of Haloalkynes

Independent control of halide substitution at six of the seven naphthalene positions of 2‐arylnaphthalenes is achieved through the regioselective benzannulation of chloro‐, bromo‐, and iodoalkynes. The modularity of this approach is demonstrated through the preparation of 44 polyheterohalogenated naphthalene products, most of which are difficult to access through known naphthalene syntheses. The outstanding regioselectivity of the reaction is both predictable and proven unambiguously by single‐crystal X‐ray diffraction for many examples. This synthetic method enables the rapid preparation of complex aromatic systems poised for further derivatization using established cross‐coupling methods. The power and versatility of this approach makes substituted naphthalenes highly attractive building blocks for new organic materials and diversity‐oriented synthesis.     

Dynamics of Fluorescent Dyes Attached to G‐Quadruplex DNA and their Effect on FRET Experiments

FRET spectroscopy is a promising approach for investigating the dynamics of G‐quadruplex DNA folds and improving the targeting of G‐quadruplexes by potential anticancer compounds. To better interpret such experiments, classical and replica‐exchange molecular dynamics simulations and fluorescence‐lifetime measurements are used to understand the behavior of a range of Cy3‐based dyes attached to the 3′ end of G‐quadruplex DNA. The simulations revealed that the dyes interact extensively with the G‐quadruplex. Identification of preferred dye positions relative to the G‐quadruplex in the simulations allows the impact of dye–DNA interactions on FRET results to be determined. All the dyes show significant deviations from the common approximation of being freely rotating and not interacting with the host, but one of the Cy3 dye analogues is slightly closer to this case.     

Onion‐like Multifunctional Microtrap Vehicles for Attraction–Trapping–Destruction of Biological Threats

A multifunctional motile microtrap is developed that is capable of autonomously attracting, trapping, and destroying pathogens by controlled chemoattractant and therapeutic agent release. The onion‐inspired multi‐layer structure contains a magnesium engine core and inner chemoattractant and therapeutic layers. Upon chemical propulsion, the magnesium core is depleted, resulting in a hollow structure that exposes the inner layers and serves as structural trap. The sequential dissolution and autonomous release of the chemoattractant and killing agents result in long‐range chemotactic attraction, trapping, and destruction of motile pathogens. The dissolved chemoattractant (l ‐serine) significantly increases the accumulation and capture of motile pathogens (E. coli) within the microtrap structure, while the internal release of silver ions (Ag⁺) leads to lysis of the pathogen accumulated within the microtrap cavity.     

Is combining meta‐GGA correlation functionals with the OPTX exchange functional useful?

The recent generalized gradient approximation (GGA) density functional OCS1 of Handy and Cohen is implemented in the deMon code and tested on a carefully selected set of problems. OCS1 is found to be accurate for molecular atomization energies, transition metal–ligand bonds, and systems with intramolecular hydrogen bonds. However, OCS1 encounters problems for systems with intermolecular hydrogen bonds. It also tends to elongate bond lengths systematically, and sometimes significantly. The OPTX exchange is combined with three meta‐GGA correlation functionals, Lap3, τ1, and τ2, the latter reported for the first time. The new meta‐GGA scheme OPTX exchange plus τ2 correlation called Oτ2 yields improved molecular geometries, NMR shielding constants, and an improved barrier height for the H+H₂ reaction. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

An expedient synthesis of the fibril binding compound FSB via sequential Pd-catalyzed coupling reactions

The styryl benzene derivative (E, E)-1-fluoro-2,5-bis(3-hydroxycarbonyl-4-hydroxy)styrylbenzene (FSB), well-known for its binding to beta-amyloid peptide fibrils, was synthesized in an efficient manner exploiting two sequential palladium(0)-catalyzed coupling reactions in a 34% overall yield. This is a substantial improvement to the previously reported synthesis of FSB in 1.1%.