New,Non‐quinone Fluorogeldanamycin Derivatives Strongly Inhibit Hsp90

Streptomyces hygroscopicus is a natural producer of geldanamycin. Mutasynthetic supplementation of an AHBA‐blocked mutant with all possible monofluoro 3‐aminobenzoic acids provided new fluorogeldanamycins. These showed strong antiproliferative activity and inhibitory effects on human heat shock protein Hsp90. Binding to Hsp90 in the low nanomolar range was determined from molecular modelling, AFM analysis and by calorimetric studies.     

Biofilm formation capacity of Listeria monocytogens strains isolated from soft cheese from Costa Rica

Listeria monocytogenes is a bacteria associated with the production of severe infectious disease in human being, but also with the formation of biofilms in different surfaces related to the food production environment. Biofilm represents a serious problem in food industry, since it is a constant and important contamination source and also, bacteria present in it have an increased resistance towards physical and chemical agents of common use. The capacity of biofilm formation of L. monocytogenes strains previously isolated from soft cheese samples from Costa Rica was studied under different temperature and culture conditions. The microplate technique was performed using different culture media (BHIB, TSB 1:20 and cheese serum) and at different incubation temperatures (refrigeration, environmental and 35 degrees C). Biofilm formation capacity was classified according to the optical density obtained at 620 nm. None of the strains evaluated was classified as strong biofilm former under any of the variables studied, nevertheless, weak and moderate formers were detected. The results obtained show the influence of the nutrient content of the culture media used over biofilm formation; BHIB was the only culture media that allowed the expression of moderate biofilm forms, contrary to cheese serum that did not promote biofilm production. Biofilm formation is a multifactorial process, where adsorption level depends on several variables and its study must be promoted in order to develop methodologies that allow its reduction or elimination, so food industries may offer safe food products to consumers.     

Stiffness alterations of single cells induced by UV in the presence of nanoTiO2

Nanocrystalline titanium dioxide (nanoTiO2) has been reported to generate reactive oxygen species (ROS) under UV illumination. In our studies, changes in mechanical properties of human skin fibroblasts, exposed to the oxidative stress induced in the presence of nanoTiO2 and UV light, were studied using atomic force microscopy (AFM). The exposure of cells to the action of ROS was performed at low TiO2 concentration (4 microg/mL) and under illumination with low-intensity UVA (8 and 20 mW/cm2) or UVC (0.1 mW/ cm2). AFM measurements of the cell stiffness were carried out immediately after exposure of cells to the oxidative stress. The data suggest that under illumination with low-intensity UVA nanoTiO2 generates ROS, which, in turn, damage cellular and subcellular structures. This process was detected by AFM as a marked drop in the cellular stiffness of ca. 30-75%, which occurred rapidly, in the time frame of 1 min. The photo-oxidative stress inducing the decrease of cell stiffness was cancelled in the presence of a well-established antioxidant, beta-carotene. The results highlight the sensitivity of AFM to detect early changes in mechanical properties of cells exposed to oxidative stress.     

Crosslinking and grafting ethylene vinyl acetate copolymer with accelerated electrons in the presence of polyfunctional monomers

In this study, we have studied the effects of polyfunctional monomers (PFMs) on physical properties of ethylene vinyl acetate (EVA) copolymer crosslinked with electron beam (EB) or peroxides. The PFMs used were triallylcyanurate, triallylisocyanurate, trimethylolpropane trimethacrylate, zinc diacrylate, and ethylene glycol dimethacrylate. Using PFMs has led to (1) optimum cure time t ₉₀ decrease from 19′25″ to 17′30″–18′45″, (2) scorch time increase from 2′ to maximum 3′45″, (3) increasing the crosslink density of peroxide or EB-cured systems by increasing the efficiency of productive radical reactions. The most efficient PFM for EVA copolymer blends has been triallylisocyanurate. Tensile strength and tear strength of samples crosslinked with EB for all irradiation doses are significantly better than those obtained for samples crosslinked with peroxides (differences up to 190%). The results show that EB irradiation gave the best results     

Ultra dispersed particles of Fe(III) compounds in the strongly basic crosslinked ionic polymer-precursors for new sorbents and catalysts

The Mössbauer spectroscopy and SEM investigation shows that crosslinked ionic polymers containing strongly basic functional groups adsorb Fe(III)-containing cations from sulphate solution through the formation in the polymer phase of high dispersed particles of jarosite mineral type compounds. Using different procedures the particles sizes and morphology, their repartition on the surface and in the volume of the polymer granule, the composition of the “polymer-inorganic compound” structural units were modified that is important for sorbents and catalysts obtaining. On heating in water medium in a boiling water bath, a part of the jarosite type compounds in the polymer phase is converted into ultra fine β-FeOOH particles in superparamagnetic state and the rest, in relatively massive and magnetically ordered β-FeOOH particles. The higher is the content of the Fe(III) in the polymer phase, the shorter is the duration of heating in water for the appearance of relatively massive particles of β-FeOOH. The particles of the jarosite type compounds and of the β-FeOOH are formed both on the surface and in the volume of the polymer granule. Upon heating in water, a part of the Fe(III)-containing particles have migrated from the volume of the polymer granule to the surface. Thermogravimetric investigation (in an N₂ atmosphere) shows that on heating of the Fe(III)-containing polymer sample up to 900 °C, complicated processes take place.     

Optical,electrical and morphological properties of transparent binary doped polyaniline thin films synthesized by in situ chemical bath deposition

The development of polymeric thin films has attracted attention in the optoelectronics field due to their transparency. The aim of the research presented was to obtain transparent polyaniline thin films by easy in situ oxidative polymerization of aniline with ammonium persulfate in the presence of a binary doping agent–poly(vinyl alcohol) mixture. Poly(acrylic acid), 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid or sodium dodecylsulfate were mixed with hydrochloric acid to form the binary doping agents. Polyaniline thin films were produced during aniline polymerization on Corning glass slides immersed in the mixture in order to study their optical, electrical and morphological properties. The optical absorption coefficient and the energy band gap were evaluated by optical transmission of the films in the UV‐visible spectral region. The optical absorption coefficient of all polyaniline films was of the order of 10⁴ cm^?1 with a maximum transmittance up to 80% at 550 nm. In order to investigate the effect of the mixture on the surface morphology and roughness of the films, atomic force microscopy was used. In general, surface roughness was reduced threefold by adding a mixture and optical transmission was increased by 20–30% without significantly affecting the absorption coefficient and the band gap of polyaniline. Islands and needle‐like structures on the film surfaces were obtained from various mixtures affecting the conductivity; for example, 0.17 S cm^?1 was obtained from needle‐like morphology, while 1.9 × 10^?4 S cm^?1 was obtained from island morphology. Raman spectroscopy studies confirmed the presence of poly(vinyl alcohol) in the thin films. Copyright © 2011 Society of Chemical Industry