Green Nanocoatings Prepared by Crosslinking Self-Assembled Fatty Acids on Metals

Self-assembled monolayers (SAMs) are an important element of modern nanotechnology and surface functionalization. However, their application is still limited because they are easily removed from the surface of the object in corrosive environments. Crosslinking would make SAMs more resistant to the corrosive environment they are exposed to. In this work, how to strongly crosslink SAMs made of non-toxic and biodegradable fatty acids on metal surfaces using ionizing radiation has been demonstrated for the first time. The crosslinked nanocoatings are stable over time and have significantly improved properties compared to SAMs. Thus, crosslinking opens up the possibility of using SAMS in a variety of different systems and on different materials for surface functionalization to achieve stable and durable surface properties such as biocompatibility or selective reactivity.     

The influence of oxide nanoparticles on the kinetics of free radical methyl methacrylate polymerization in bulk

A series of poly(methyl methacrylate) (PMMA) nanocomposites were synthesized using free radical polymerization in bulk, by addition of 1 vol% of oxide nanoparticles (silica, alumina, and titania), differing in the nature and type. The influence of nanofiller presence on the kinetics of methyl methacrylate (MMA) free radical polymerization was investigated. For this purpose, the kinetic model that includes the contribution from the first‐order reaction and the autoacceleration was applied on data obtained following the isothermal polymerization at 70°C by differential scanning calorimetry (DSC). The effect of the size and the surface nature of nanofillers on the interfacial layer thickness (d), as well as the influence of d on the glass transition temperature (T_g) of PMMA hybrid materials was studied. It was found that hydrophilic particles accelerated the initiator decomposition and affected the monomer polymerization on the surface, which caused the formation of thicker interfacial layer compared to the one around hydrophobic fillers. The addition of smaller nanoparticles size decreased the glass transition temperature of pure poly(methyl metacrylate). The linear increase of PMMA T_g value with increasing the polymeric interfacial layer was determined. The T_g values of pure PMMA and PMMA nanocomposite with d of 1.4 nm were estimated to be the same. POLYM. COMPOS. 34:1342–1348, 2013. © 2013 Society of Plastics Engineers     

Connexin Expression Is Altered in Liver Development of Yotari (dab1 -/-) Mice

Disabled-1 (Dab1) protein is an intracellular adaptor of reelin signaling required for prenatal neuronal migration, as well as postnatal neurotransmission, memory formation and synaptic plasticity. Yotari, an autosomal recessive mutant of the mouse Dab1 gene is recognizable by its premature death, unstable gait and tremor. Previous findings are mostly based on neuronal abnormalities caused by Dab1 deficiency, but the role of the reelin signaling pathway in nonneuronal tissues and organs has not been studied until recently. Hepatocytes, the most abundant cells in the liver, communicate via gap junctions (GJ) are composed of connexins. Cell communication disruption in yotari mice was examined by analyzing the expression of connexins (Cxs): Cx26, Cx32, Cx37, Cx40, Cx43 and Cx45 during liver development at 13.5 and 15.5 gestation days (E13.5 and E15.5). Analyses were performed using immunohistochemistry and fluorescent microscopy, followed by quantification of area percentage covered by positive signal. Data are expressed as a mean ± SD and analyzed by one-way ANOVA. All Cxs examined displayed a significant decrease in yotari compared to wild type (wt) individuals at E13.5. Looking at E15.5 we have similar results with exception of Cx37 showing negligible expression in wt. Channels formation triggered by pathological stimuli, as well as propensity to apoptosis, was studied by measuring the expression of Pannexin1 (Panx1) and Apoptosis-inducing factor (AIF) through developmental stages mentioned above. An increase in Panx1 expression of E15.5 yotari mice, as well as a strong jump of AIF in both phases suggesting that yotari mice are more prone to apoptosis. Our results emphasize the importance of gap junction intercellular communication (GJIC) during liver development and their possible involvement in liver pathology and diagnostics where they can serve as potential biomarkers and drug targets.     

19F NMR study of the leucine-specific binding protein of Escherichia coli: mutagenesis and assignment of the 5-fluorotryptophan-labeled residues

The Escherichia coli L-leucine receptor is an aqueous proteinand the first component in the distinct transport pathway forhydrophobic amino acids. L-Leucine binding induces a conformationalchange, which enables the receptor to dock to the membrane components.To investigate the ligand-induced conformational change andbinding properties of this protein, we used ¹⁹F NMR to probethe four tryptophan residues located in the two lobes of theprotein. The four tryptophan residues were labeled with 5-fluorotryptophanand assigned by site-directed mutagenesis. The ¹⁹F NMR spectraof the partially ligand free proteins show broadened peaks whichsharpen when L-leucine is bound, showing that the labeled wild-typeprotein and mutants are functional. The titration of L-phenylalanineinto the 5-fluorotryptophan labeled wild-type protein showsthe presence of closed and open conformers. Urea-induced denaturationstudies support the NMR results that the wild-type protein bindsL-phenylalanine in a different manner to L-leucine. Our studiesshowed that the tryptophan to phenylalanine mutations on structuralunits linked to the binding pocket produce subtle changes inthe environment of Trp18 located directly in the binding cleft.     

Motivational factors in departure of young scientists from Croatian science

The noticeable tendency of young Croatian scientists towards a professional and foreign exodus can be explained not so much by their social, professional or material differentiation as by a subjective experience of their own life and professional situation; in other words, dissatisfaction of the researchers with their own professional and social status. The hierarchy of motives of a potential young scientists" drain indicates a complex pattern. It combines suppressive yet attractive motives where economic factors take precedence but with a desire for better conditions in scientific work and opportunities for promotion, thus demonstrating a motivational duality: integration into the general motivational migration pattern while displaying a scientifically motivational specificity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Preparation of smallest microparticles of poly-D,L-lactide by modified precipitation method: influence of the process parameters

Biodegradable microspheres such as those made of poly-D,L-lactide (PDLLA) are widely investigated delivery systems for drugs or antigens. The aim of this study was to examine experimental conditions in order to produce PDLLA microspheres with the best properties for controlled and sustained drug delivery by the modified precipitation method. For this purpose, the following parameters were varied: co-solvent (methanol or ethanol), the concentration of stabilizer polyvinyl alcohol (PVA), chloroform-to-water ratio and the speed and time of homogenization. Scanning electron microscopy (SEM) and stereological analysis were used to characterize the particles. The average size and morphology of the microspheres varied substantially with preparation conditions from 8.44-1.25 microm. Results showed that the smallest particles were obtained with methanol, 1% PVA and with 10 min of homogenization at 21,000 rpm.     

Miscibility and thermooxidative degradation of poly(vinyl chloride)/biodegradable aliphatic–aromatic copolyester blends

The miscibility of poly(vinyl chloride) (PVC) and a biodegradable aliphatic–aromatic copolyester (AAC) was investigated by differential scanning calorimetry. The thermooxidative degradation of the blends was investigated thermogravimetrically. The blends were prepared by dissolution in 1,2‐dichloroethane and precipitation with methanol. The investigated blends were completely miscible with the glass‐transition temperatures best predicted by the Fox equation. Fourier transform infrared analysis showed that the interactions responsible for miscibility were the hydrogen bonds between the blend components. The thermooxidative stability of the PVC/AAC blends was improved compared to that of pure PVC. Furthermore, when AAC was added, the dehydrochlorination rate of PVC decreased, and the maximum rate shifted to a higher temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2158–2163, 2006     

The potential of Festuca rubra and Calamagrostis epigejos for the revegetation of fly ash deposits

Two grass species, Festuca rubra (sown) and Calamagrostis epigejos (naturally recolonised), were studied at two fly ash deposit lagoons, weathered 5 (L1) and 13 years (L2). Both species were assessed in terms of their invasive ability, photosynthetic efficiency, trace elements accumulation, and damage symptoms, while the characteristics of the habitat were assessed in terms of trace element content, and the pH and EC of the ash. In the ash weathered for 5 and 13 years, B and Mn concentrations fell within the normal range for soils, while there was an As, Mo and Cu excess, and Se and Zn deficit. There was no difference in the photosynthetic efficiency (ns) of the C. epigejos populations at the different-aged ash lagoons, but differences were found between the populations of F. rubra (P < 0.001). F. rubra displayed damage symptoms, in the form of leaf tip chlorosis and necrosis, and wilting seedlings — a result of B accumulation in toxic concentrations and a Cu and Mn deficit. After 13 years the sown F. rubra remained over 9.5% of the ash lagoon's area (L2), while over the same period the naturally recolonised C. epigejos had overgrown 87.5% of the area. The greater colonisation and survival potential of C. epigejos is a result of multiple tolerance to the conditions at ash deposits and of the competitive ability of this species to dominate the colonised habitat. Therefore, characteristics of naturally colonised species can be used for modelling future actions of biological restoration of fly ash deposits aimed at binding the ash with minimal investment (the short-term aim), and for providing conditions for revegetation, and shortening the successive phases in the revegetation of ash deposits after the closure of thermal plants (the long-term aim).     

Electrodeposition of Co-Ni-MoxOy Powders: Part I. The Influence of Deposition Conditions on Powder Composition and Morphology

The Co-Ni-Mo_xO_y powders were obtained electrochemically at a constant current density from ammonia electrolyte. Ni and Co were anomalously deposited, inducing Mo deposition, which cannot be deposited separately from aqueous solutions. The obtained Co-Ni-Mo_xO_y powders were investigated by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and scanning electon microscope (SEM) methods. Based on the obtained experimental results, it was concluded that the particle size of deposited powders is influenced by the chemical composition of the electrolyte and current density imposed. XRD results suggested that obtained powders were of amorphous structure, although a Co₃Mo compound can be formed if certain experimental conditions are applied.