Effect of a curing accelerator on the glass transition temperature of non-stoichiometric epoxy amine networks

Networks were prepared from Bisphenol A diglycidylether and 4,4′-diaminodiphenylmethane both in the presence of different amounts of imidazole and in the absence of any accelerator. The ratio of epoxy groups to amino hydrogen was varied: the networks were made with amino hydrogen excess, a stoichiometric ratio of epoxy groups to amino hydrogen, and an epoxy excess. The resulting networks were investigated by thermomechanical analysis, by torsion pendulum analysis and by uniaxial compression modulus measurements in the rubbery-plateau zone. Further characterization was done by sol gel analysis of the cured samples. It was shown that imidazole does not significantly influence the glass transition temperature and the soluble content of the samples of an excess of amino hydrogen was used. In the case of a stoichiometric ratio of epoxy groups to amino hydrogen and in the case of an epoxy excess, imidazole considerably influences the glass transition temperature of the networks. A dependence of the soluble content of the samples on imidazole concentration used for network synthesis was found mainly in epoxy excess systems.     

Implementation intentions and effective goal pursuit.

The theoretical distinction between goal intentions ("I intend to achieve x") and implementation intentions ("I intend to perform goal-directed behavior y when I encounter situation z"; P. M. Gollwitzer, 1993) is explored by assessing the completion rate of various goal projects. In correlational Study 1, difficult goal intentions were completed about 3 times more often when participants had furnished them with implementation intentions. In experimental Study 2, all participants were assigned the same difficult goal intention. and half were instructed to form implementation intentions. The beneficial effects of implementation intentions paralleled those of Study 1. In experimental Study 3, implementation intentions were observed to facilitate the immediate initiation of goal-directed action when the intended opportunity was encountered. Implementation intentions are interpreted to be powerful self-regulatory tools for overcoming the typical obstacles associated with the initiation of goal-directed actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of ether lipids on the activity and secretion of interleukin-1 and interleukin-2

Alkyl lysophospholipids (ALP) are synthetic analogues of lysophosphatidylcholine and represent a new generation of antitumor drugs currently being tested in phase-I trials in patients with cancer. The present study reports the differential modulation of human immunocompetent cells in vitro by ALP. Serum-bound ALP effectively blocked the response of growth factor-dependent cells to interleukin-2 (IL-2), inhibited the cellular production and release of IL-2 and suppressed the comitogenic effect of interleukin-1 (IL-1) on mouse thymocytes. In contrast, ALP-primed, monocyte-derived macrophages (MO) lost their ability to release IL-1 in response to stimuli like lipopolysaccharides (LPS) during terminal maturation from monocytes. Supernatants from ALP-primed, LPS-induced MO possessed costimulatory as well as direct mitogenic activity. Neither ALP alone nor ALP-conditioned MO supernatants stimulated mouse thymocytes. Priming of MO by ET-18-OH, an ALP molecule not substituted in thesn-2 position, occurred at concentrations 4- to 16-fold higher than the most active compounds ET-18-OCH, and the thioether analogue BM 41.440. ALP also primed MO for subsequent activation of tumor cytotoxicity by LPS and interferon-gamma. IL-1 has multiple biological activities in common with ALP, and it may mediate antitumor activity and other ALP effects in vivo. The ability of ALP to induce differential immunomodulation, as demonstrated in this study, may make ALP worthy of study for the therapy of both autoimmune and neoplastic disease.     

Fabrication and functionalization of single asymmetric nanochannels for electrostatic/hydrophobic association of protein molecules

We have developed a facile and reproducible method for surfactant-controlled track-etching and chemical functionalization of single asymmetric nanochannels in PET (polyethylene terephthalate) membranes. Carboxyl groups present on the channel surface were converted into pentafluorophenyl esters using EDC/PFP (N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/pentafluorophenol) coupling chemistry. The resulting amine-reactive esters were further covalently coupled with ethylenediamine or propylamine in order to manipulate the charge polarity and hydrophilicity of the nanochannels, respectively. Characterization of the modified channels was done by measuring their current-voltage (I-V) curves as well as their permselectivity before and after the chemical modification. The electrostatic/hydrophobic association of bovine serum albumin on the channel surface was observed through the change in rectification behaviour upon the variation of pH values.     

Synthesis and biological evaluation of N-acylhydrazones as inhibitors of MurC and MurD ligases

The Mur ligases have an essential role in the intracellular biosynthesis of bacterial peptidoglycan, and they represent attractive targets for the design of novel antibacterials. A series of compounds with an N-acylhydrazone scaffold were synthesized and screened for inhibition of the MurC and MurD enzymes from Escherichia coli. Compounds with micromolar inhibitory activities against both MurC and MurD were identified, and some of them also showed antibacterial activity.     

Study of the remediation of a site contaminated with arsenic

Soil and rock-like material was collected from a former industrial site (arsenic factory) in order to study the degree to which the site is contaminated. Characterisation of the soil and rock-like samples indicated that the site is highly contaminated with arsenic: the soil material contains 2.5–3.5% (dry wt.%) of arsenic, the rock-like material up to 20%. According to Flemish norms (VLAREBO, 1996) concerning the contamination of soils for industrial sites, remediation of the soil is required on a short-term basis when a value of 300 mg As/kg of dry solid is exceeded. In this paper, solidification/stabilisation with cement and/or lime for remediation of the site was studied. If later the solidified site material is landfilled, one of the criteria is that the arsenic concentration in the leachate, determined according to the DIN 38 414 S4 extraction test (Deutsches Institut für Normung, 1984), must be lower than 1 mg/l (VLAREM II, 1995). Solidification proved to be an efficient method to lower the amount of arsenic leached from the material to below the norm of 1 mg/l. The results of a semi-dynamic leach test indicated that arsenic was released very slowly from the solidified material: over the period of the leach test only 0.10% of the arsenic initially present was leached.     

A multiplexed protein kinase assay

We report a novel protein kinase assay designed for high-throughput detection of one or many kinases in a complex mixture. A solution-phase phosphorylation reaction is performed on 900 different peptide substrates, each covalently linked to an oligonucleotide tag. After incubation, phosphoserine, phosphothreonine, and phosphotyrosine are chemically labeled, and the substrates are hybridized to a microarray with oligonucleotides complementary to the tags to read out the phosphorylation state of each peptide. Because protein kinases act on more than one peptide sequence, each kinase can be characterized by a unique signature of phosphorylation activity on multiple substrates. Using this method, we determined signatures for 26 purified kinases and demonstrated that enzyme mixtures can be screened for activity and selectivity of inhibition.     

Architecture as Initiative (A Manifesto)

Estonian architect Veronika Valk of Zizi&Yoyo provides a manifesto for contemporary practice, based on ‘architecture as initiative’; initiative being defined as the basic catalyst for change in a project, whether it is a small-scale art installation or an urban development. As self-contained ideas factories, initiatives generate ‘open and affirmative ways to approach innovation in architecture’.     

Expansion of Access Tunnels and Active‐Site Cavities Influence Activity of Haloalkane Dehalogenases in Organic Cosolvents

The use of enzymes for biocatalysis can be significantly enhanced by using organic cosolvents in the reaction mixtures. Selection of the cosolvent type and concentration range for an enzymatic reaction is challenging and requires extensive empirical testing. An understanding of protein–solvent interaction could provide a theoretical framework for rationalising the selection process. Here, the behaviour of three model enzymes (haloalkane dehalogenases) was investigated in the presence of three representative organic cosolvents (acetone, formamide, and isopropanol). Steady‐state kinetics assays, molecular dynamics simulations, and time‐resolved fluorescence spectroscopy were used to elucidate the molecular mechanisms of enzyme–solvent interactions. Cosolvent molecules entered the enzymes' access tunnels and active sites, enlarged their volumes with no change in overall protein structure, but surprisingly did not act as competitive inhibitors. At low concentrations, the cosolvents either enhanced catalysis by lowering K_0.5 and increasing k_cat, or caused enzyme inactivation by promoting substrate inhibition and decreasing k_cat. The induced activation and inhibition of the enzymes correlated with expansion of the active‐site pockets and their occupancy by cosolvent molecules. The study demonstrates that quantitative analysis of the proportions of the access tunnels and active‐sites occupied by organic solvent molecules provides the valuable information for rational selection of appropriate protein–solvent pair and effective cosolvent concentration.