DNA based multi-copper ions assembly using combined pyrazole and salen ligandosides

The DNA structure is an ideal building block for the construction of functional nano-objects. In this direction, metal coordinating base pairs (ligandosides) are an appealing tool for the future specific functionalization of such nano-objects. We present here a study, in which we combine the metal ion coordinating pyrazole ligandoside with the interstrand crosslinking salen ligandoside system. We show that both ligandosides, when combined, are able to create stable multi-copper ion complexing DNA double helix structures in a cooperative fashion.     

Two aspects of water in self-heating risk of aluminium powders: calorimetric study

Journal of Thermal Analysis and Calorimetry - Two samples (“O” and “C”) of aluminium-based powders were calorimetrically investigated with respect to the self-heating risk...     

Preparation and characterization of microcapsules loaded with polyphenols-enriched Uncaria tomentosa extract using spray-dryer technique

Journal of Thermal Analysis and Calorimetry - This work prepared and characterized microcapsule of Uncaria tomentosa (UT) in order to standardize a spray-dryer Uncaria tomentosa extract. The UT...     

Shape-Adaptability and Redox-Switching Properties of a Di-Gold Metallotweezer

The use of a carbazolyl-connected di-gold(I) metallotweezer for the encapsulation of several electron-poor organic substrates, and a planar Au(III) complex containing a CNC pincer ligand, is described. The binding affinity of the receptor depends on the electron-deficient character of the planar guest, with larger association constants found for the more electron-poor guests. The X-ray diffraction molecular structures of two host:guest adducts show that the host approaches its arms in order to facilitate the optimum interaction with the surface of the planar guests, in a clear example of an guest-induced fit conformational arrangement. The electrochemical studies of the encapsulation of N,N’-dimethyl-naphthalenetetracarboxy diimide (NTCDI) show that the redox active guest is released from the receptor upon one electron reduction, thus constituting an example of redox-switchable binding.     

Improving stability and thermal properties of TiO2-based nanofluids for concentrating solar energy using two methods of preparation

Journal of Thermal Analysis and Calorimetry - Nanofluids are considered a promising alternative to the classic fluids used in heat transfer processes. One interesting application of nanofluids is...     

On the geometric–arithmetic index by decompositions-CMMSE

The concept of geometric–arithmetic index was introduced in the chemical graph theory recently, but it has shown to be useful. There are many papers studying different kinds of indices (as Wiener, hyper–Wiener, detour, hyper–detour, Szeged, edge–Szeged, PI, vertex–PI and eccentric connectivity indices) under particular cases of decompositions. The main aim of this paper is to show that the computation of the geometric-arithmetic index of a graph G is essentially reduced to the computation of the geometric-arithmetic indices of the so-called primary subgraphs obtained by a general decomposition of G. Furthermore, using these results, we obtain formulas for the geometric-arithmetic indices of bridge graphs and other classes of graphs, like bouquet of graphs and circle graphs. These results are applied to the computation of the geometric-arithmetic index of Spiro chain of hexagons, polyphenylenes and polyethene.     

Immobilization and Stabilization of Beta-Xylosidases from Penicillium janczewskii

β-Xylosidases are critical for complete degradation of xylan, the second main constituent of plant cell walls. A minor β-xylosidase (BXYL II) from Penicillium janczewskii was purified by ammonium sulfate precipitation (30% saturation) followed by DEAE-Sephadex chromatography in pH 6.5 and elution with KCl. The enzyme presented molecular weight (MW) of 301 kDa estimated by size exclusion chromatography. Optimal activity was observed in pH 3.0 and 70–75 °C, with higher stability in pH 3.0–4.5 and half-lives of 11, 5, and 2 min at 65, 70, and 75 °C, respectively. Inhibition was moderate with Pb⁺² and citrate and total with Cu⁺², Hg⁺², and Co⁺². Partially purified BXYL II and BXYL I (the main β-xylosidase from this fungus) were individually immobilized and stabilized in glyoxyl agarose gels. At 65 °C, immobilized BXYL I and BXYL II presented half-lives of 4.9 and 23.1 h, respectively, therefore being 12.3-fold and 33-fold more stable than their unipuntual CNBr derivatives (reference mimicking soluble enzyme behaviors). During long-term incubation in pH 5.0 at 50 °C, BXYL I and BXYL II glyoxyl derivatives preserved 85 and 35% activity after 25 and 7 days, respectively. Immobilized BXYL I retained 70% activity after 10 reuse cycles of p-nitrophenyl-β-D-xylopyranoside hydrolysis.

     

Antimicrobial activity of newly synthesized thienoquinolizidines derivatives: inspired by natural plant alkaloids

The antimicrobial activity of 16 newly prepared quinolizidines derivatives using bacteria (Staphylococcus aureus, Staphylococcus epidermidis, Proteus sp., Escherichia coli) acid fast bacterium Mycobacterium smegmatis, yeasts (Candida albicans, Candida parapsilosis), and filamentous fungi (Fusarium culmorum, Microsporum gypseum, Aspergillus flavus, Botrytis cinerea, Alternaria alternata) was studied in this paper. The best antibacterial properties were demonstrated by derivatives 11Ba, trans10Bb and 11Bb, and the most sensitive microorganism was found to be the gram-positive bacterium S. epidermidis. The derivative 11Bb showed the best antifungal activity, while C. albicans was resistant to all tested derivatives, and C. parapsilosis was fully inhibited in the presence of the derivative 11Ba and 11Bb. Among the filamentous fungi, only the dermatophyte M. gypseum was partially inhibited. Biofilms represent the most prevalent type of microbial growth in nature and are crucial to the development of clinical infections. Newly synthesized derivatives were also added into the medium throughout the biofilm formation. We have observed a significant decrease of biofilm formation in the presence of quinolizidine derivatives, testifying to their significant antimicrobial activity. It seems that the relationship between antimicrobial activity and the structure is based on the alkaline character due to nitrogen, the saturated basic quinolizidine skeleton, and the position of sulfur in the molecule.     

Utilization of GDOES for the study of friction layers formed on the surface of brake discs during the friction process

The paper deals with the chemical characterization of friction layer, generated on the surface of friction materials during the friction test using the glow discharge optical emission spectrometry (GDOES). Friction layer is formed during the friction process and its character depends on several factors. One of the most important factors is the material composition of brake pads and brake disc. When the brake pressure is released at the end of the braking event, the specific friction layer remains on the surface of both pairs (brake pads and brake disc). Using the GDOES profile analysis, the thicknesses of friction layers were estimated and these results were compared with results obtained by scanning electron microscopy together with X-ray microanalysis.