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Dasireddy V.D.B.C.,National Institute of Chemistry, Slovenia | Likozar B.,National Institute of Chemistry, Slovenia
Fuel | Year: 2017

Production of hydrogen without any carbon dioxide or monoxide is of utmost importance for the chemical energy storage and conversion in a future low-carbon economy. Alumina-supported copper and Cu/Zn/Al2O3 catalysts were prepared by incipient wetness- and ultrasonic impregnation, while Zn/Al2O3 catalysts were also prepared to compare the effect of Zn. The characterisation of catalysts was carried out by N2 physisorption, XRD, H2-TPR, N2O chemisorption, NH3-TPD, CO2-TPD, H2-TPD, XPS and TEM. Catalysts prepared via ultrasonic impregnation showed a high metal dispersion and a small crystallite size, whereas Lewis acidic and basic sites were predominant on all catalysts, while the acid–base strength was strongly influenced by the presence of zinc in the case of Cu/Zn/Al2O3 catalysts. A high catalytic activity, reflected through the almost total conversion of ammonia at 600 °C with the H2 production rate of 36.2 mmol g−1 min−1, was achieved over Cu/Zn/Al2O3 catalyst, prepared by ultrasonic impregnation. The dispersion of metal and its acidic or basic nature played an important role, even more so than the presence of the two or three potentially synergistic metals on the surface of a catalyst. Under the applied reaction conditions, the catalysts showed an excellent stability for more than 100 h. © 2017 Elsevier Ltd


Cotman A.E.,University of Ljubljana | Cahard D.,INSA Rouen | Mohar B.,National Institute of Chemistry, Slovenia
Angewandte Chemie - International Edition | Year: 2016

CF3-substituted 1,3-diols were stereoselectively prepared in excellent enantiopurity and high yield from CF3-substituted diketones by using an ansa-ruthenium(II)-catalyzed asymmetric transfer hydrogenation in formic acid/triethylamine. The intermediate mono-reduced alcohol was also obtained in very high enantiopurity by applying milder reaction conditions. In particular, CF3C(O)-substituted benzofused cyclic ketones underwent either a single or a double dynamic kinetic resolution during their reduction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Cevec M.,National Institute of Chemistry, Slovenia | Thibaudeau C.,National Institute of Chemistry, Slovenia | Plavec J.,National Institute of Chemistry, Slovenia | Plavec J.,University of Ljubljana
Nucleic Acids Research | Year: 2010

We have determined the 3D structure of a 34-nt RNA construct, herein named LCS1co, which mimics the interaction of let-7 microRNA (miRNA) to one of its complementary binding sites, LCS1, in the 3′-untranslated region of lin-41 mRNA by solution-state NMR spectroscopy. let-7 miRNAs control the timing of development of the nematode Caenorhabditis elegans and are highly conserved in mammals. The sequence and structure of the two conserved let-7 complementary sites, LCS1 and LCS2, in the 3′-untranslated region of lin-41 mRNA are important for a proper downregulation of lin-41. The high-resolution NMR structure reveals details of the binding of let-7 miRNA to lin-41 mRNA which involves formation of a complex with non-canonical structural elements within the seed region. LCS1co exhibits a stem-loop structure with two stems, an asymmetric internal loop and an adenine bulge. Comparison with the NMR solution-state structure of the let-7:lin-41 complex involving the LCS2-binding site shows that conformational freedom of the asymmetric internal loop of LCS1co correlates with a smaller bend between the upper and lower stems in comparison to the well-defined asymmetric loop of LCS2co. © 2010 The Author(s).


Veryasov G.,Jozef Stefan Institute | Grilc M.,National Institute of Chemistry, Slovenia | Likozar B.,National Institute of Chemistry, Slovenia | Jesih A.,Jozef Stefan Institute
Catalysis Communications | Year: 2014

The synthesis of urchin-like crystalline MoS2 with micron unit size and surface area of 25 m2 g- 1 and its application for the catalytic hydrogenation and hydrodeoxygenation (HDO) of liquefied wood sample are reported. We observed significant increase of deoxygenation rate considering intensities of CO and OH band intensities in liquid phase IR spectra. Prepared catalyst exhibited higher activity compared to commercial MoS2 powder. Elemental analysis of organic phase after HDO revealed equal elemental compositions for both samples, with higher yield in case of urchin-like MoS2. Oxygen content decreased from 43.3% to 8.2% (wt.); residual phenolic oxygen is not removable with catalyst described. Observed catalytic performance may provide new solutions in terms of biofuel processing. © 2013 Published by Elsevier B.V.


Klofutar B.,ZORD Slovenija | Golob J.,University of Ljubljana | Likozar B.,University of Ljubljana | Klofutar C.,University of Ljubljana | And 2 more authors.
Bioresource Technology | Year: 2010

We have investigated the transesterification of rapeseed (RO) and waste sunflower (SO) oils with methanol in the presence of potassium hydroxide as a catalyst. The transesterification of tri-acylglycerols was first conducted in a batch reactor. The effect of the temperature on the reaction rates was studied at a constant molar ratio of the alcohol to tri-acylglycerols (6:1) and for a constant concentration of the catalyst (1.0 wt%). Size-exclusion chromatography and 1H NMR spectroscopy were used to quantitatively monitor the transesterification reaction. The mass-transfer coefficients of the tri-acylglycerols during the initial transesterification stage were found to be 0.2-1.2 × 10-5 m min-1, depending on the type of oil and the temperature. Calculated activation energies implied that at higher temperatures the formation of mono-acylglycerols and glycerole was favored for the SO (93 kJ/mol for the forward and 48 kJ/mol for the backward reaction) and the RO (47 kJ/mol for the forward and 36 kJ/mol for the backward reaction), respectively. For the continuous industrial reactor/separator setup, the optimum methanol recycle ratio was established as 0.0550. © 2010 Elsevier Ltd. All rights reserved.


Pfaffenhuber C.,Max Planck Institute for Solid State Research | Sorgel S.,Max Planck Institute for Solid State Research | Weichert K.,Max Planck Institute for Solid State Research | Bele M.,National Institute of Chemistry, Slovenia | And 3 more authors.
Journal of the American Chemical Society | Year: 2011

The formation of fractal silica networks from a colloidal initial state was followed in situ by ion conductivity measurements. The underlying effect is a high interfacial lithium ion conductivity arising when silica particles are brought into contact with Li salt-containing liquid electrolytes. The experimental results were modeled using Monte Carlo simulations and tested using confocal fluorescence laser microscopy and γ-potential measurements. © 2011 American Chemical Society.


Koprivnjak T.,National Institute of Chemistry, Slovenia | Peschel A.,University of Tübingen
Cellular and Molecular Life Sciences | Year: 2011

Host defense peptides and proteins are important components of the innate host defense against pathogenic microorganisms. They target negatively charged bacterial surfaces and disrupt microbial cytoplasmic membranes, which ultimately leads to bacterial destruction. Throughout evolution, pathogens devised several mechanisms to protect themselves from deleterious damage of host defense peptides. These strategies include (a) inactivation and cleavage of host defense peptides by production of host defense binding proteins and proteases, (b) repulsion of the peptides by alteration of pathogen's surface charge employing modifications by amino acids or amino sugars of anionic molecules (e.g., teichoic acids, lipid A and phospholipids), (c) alteration of bacterial membrane fluidity, and (d) expulsion of the peptides using multi drug pumps. Together with bacterial regulatory network(s) that regulate expression and activity of these mechanisms, they represent attractive targets for development of novel antibacterials. © Springer Basel AG 2011.


Poblete S.,Max Planck Institute for Polymer Research | Praprotnik M.,Max Planck Institute for Polymer Research | Praprotnik M.,National Institute of Chemistry, Slovenia | Kremer K.,Max Planck Institute for Polymer Research | Delle Site L.,Max Planck Institute for Polymer Research
Journal of Chemical Physics | Year: 2010

Simulation schemes for liquids or strongly fluctuating systems that allow to change the molecular representation in a subvolume of the simulation box while preserving the equilibrium with the surroundings introduce conceptual problems of thermodynamic consistency. In this work we present a general scheme based on thermodynamic arguments which ensures a thermodynamic equilibrium among molecules of different representations. The robustness of the algorithm is tested for two examples, namely, an adaptive resolution simulation, atomistic/coarse grained, for a liquid of tetrahedral molecules, and an adaptive resolution simulation of a binary mixture of tetrahedral molecules and spherical solutes. © 2010 American Institute of Physics.


Ristic A.,National Institute of Chemistry, Slovenia | Maucec D.,National Institute of Chemistry, Slovenia | Henninger S.K.,Fraunhofer Institute for Solar Energy Systems | Kaucic V.,National Institute of Chemistry, Slovenia
Microporous and Mesoporous Materials | Year: 2012

A new two-component (composite) water sorbent CaCl 2-FeKIL2 has been developed for sorption-based solar thermal energy storage. The matrix of the composite is FeKIL2 material with disordered mesopores, high surface area of 712 m 2/g and mesopore dimensions between 4 and 29 nm. The composite, prepared by wet impregnation of FeKIL2 with CaCl 2, has lower surface area (418 m 2/g) and similar mesopore dimensions as the matrix. The maximum water sorption capacity of FeKIL2 is 0.21 g/g, while the composite possesses 3 times higher maximum water sorption capacity due to the presence of the salt in the matrix. Heat of adsorption of the composite is 50.4 kJ/mol. A short-term cycling test between temperatures of 150 and 40°C at a water vapour pressure of 5.6 kPa confirms a comparatively good hydrothermal stability of the composite. © 2012 Elsevier Inc. All rights reserved.


Koprivnjak T.,National Institute of Chemistry, Slovenia | Zhang D.,University of Iowa | Ernst C.M.,University of Tübingen | Pesche A.,University of Tübingen | And 2 more authors.
Journal of Bacteriology | Year: 2011

In many bacteria, including Staphylococcus aureus, progression from the logarithmic to the stationary phase is accompanied by conversion of most of bacterial membrane phosphatidylglycerol (PG) to cardiolipin (CL). Phagocytosis of S. aureus by human neutrophils also induces the conversion of most bacterial PG to CL. The genome of all sequenced strains of S. aureus contains two open reading frames (ORFs) predicting proteins encoded with ~30% identity to the principal CL synthase (cls) of Escherichia coli. To test whether these ORFs (cls1 and cls2) encode cardiolipin synthases and contribute to CL accumulation in S. aureus, we expressed these proteins in a cls strain of E. coli and created isogenic single and double mutants in S. aureus. The expression of either Cls1 or Cls2 in CL-deficient E. coli resulted in CL accumulation in the stationary phase. S. aureus with deletion of both cls1 and cls2 showed no detectable CL accumulation in the stationary phase or after phagocytosis by neutrophils. CL accumulation in the stationary phase was due almost solely to Cls2, whereas both Cls1 and Cls2 contributed to CL accumulation following phagocytosis by neutrophils. Differences in the relative contributions of Cls1 and Cls2 to CL accumulation under different triggering conditions suggest differences in the role and regulation of these two enzymes. © 2011, American Society for Microbiology.

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