An In Vitro Study of the Effect of Viburnum opulus Extracts on Key Processes in the Development of Staphylococcal Infections

Staphylococcus aureus is still one of the leading causes of both hospital- and community-acquired infections. Due to the very high percentage of drug-resistant strains, the participation of drug-tolerant biofilms in pathological changes, and thus the limited number of effective antibiotics, there is an urgent need to search for alternative methods of prevention or treatment for S. aureus infections. In the present study, biochemically characterized (HPLC/UPLC–QTOF–MS) acetonic, ethanolic, and water extracts from fruits and bark of Viburnum opulus L. were tested in vitro as diet additives that potentially prevent staphylococcal infections. The impacts of V. opulus extracts on sortase A (SrtA) activity (Fluorimetric Assay), staphylococcal protein A (SpA) expression (FITC-labelled specific antibodies), the lipid composition of bacterial cell membranes (LC-MS/MS, GC/MS), and biofilm formation (LIVE/DEAD BacLight) were assessed. The cytotoxicity of V. opulus extracts to the human fibroblast line HFF-1 was also tested (MTT reduction). V. opulus extracts strongly inhibited SrtA activity and SpA expression, caused modifications of S. aureus cell membrane, limited biofilm formation by staphylococci, and were non-cytotoxic. Therefore, they have pro-health potential. Nevertheless, their usefulness as diet supplements that are beneficial for the prevention of staphylococcal infections should be confirmed in animal models in the future.     

Hydration,carbonation and thermal stability of hydrates in Ca7−xSrxZrAl6O18 cement

Journal of Thermal Analysis and Calorimetry - This paper studies hydration stages and phase transformation mechanism of the Sr2+-doped calcium zirconium aluminate cement at room temperature....     

Synthesis and Applications of Carbohydrate-Based Organocatalysts

Organocatalysis is a very useful tool for the asymmetric synthesis of biologically or pharmacologically active compounds because it avoids the use of noxious metals, which are difficult to eliminate from the target products. Moreover, in many cases, the organocatalysed reactions can be performed in benign solvents and do not require anhydrous conditions. It is well-known that most of the above-mentioned reactions are promoted by a simple aminoacid, l-proline, or, to a lesser extent, by the more complex cinchona alkaloids. However, during the past three decades, other enantiopure natural compounds, the carbohydrates, have been employed as organocatalysts. In the present exhaustive review, the detailed preparation of all the sugar-based organocatalysts as well as their catalytic properties are described.     

The coordination state and valence state of selected transition metal ions in SiO2-B2O3 xerogels

A series of SiO₂-B₂O₃ xerogels with changing SiO₂/B₂O₃ mol% and doped with selected transition metal ions was prepared. These mixed oxide materials contained copper, nickel, cobalt, manganese, chromium and vanadium ions coordinated to oxygen donor atoms in water and OH groups. Extensive studies of the transition metal complexes in the xerogels by such spectral techniques as diffuse reflectance (UV-vis), electron paramagnetic resonance and fluorescence spectroscopies show that there exist Cu(II) in the coordination environment of D_4h symmetry, Ni(II) in octahedral coordination sphere, Co(II) in both tetrahedral and octahedral environments, Mn(II) preferably in the O_h coordination and Mn(III) in pseudo-octahedral sphere; then octahedrally coordinated Cr(III) ions occur in coupled pairs or clusters and V(IV) as VO²⁺ ions exist in distorted (C_4v) octahedral surrounding.     

Narrow and Stable Single Photon Emission from Dibenzoterrylene in para-Terphenyl Nanocrystals

Single organic molecules are promising photon sources for quantum technologies. In this work we show photon emission from dibenzoterrylene, a widely used organic emitter, in a new host matrix, para-terphenyl. We present a reprecipitation growth method that produces para-terphenyl nanocrystals which are ideal for integration into nanophotonic devices due to their small size. We characterise the optical properties of dibenzoterrylene in nanocrystals at room and cryogenic temperatures, showing bright, narrow emission from a single molecule. Spectral data on the vibrational energies is presented and a further 25 additional molecules are characterised. This emitter-host combination has potential for quantum technology purposes with wavelengths suitable for interfacing with quantum memories.     

Synthesis of a Novel Glycopeptide by Polymeranalogous Reaction of Gelatin with Mono‐6‐para‐toluenesulfonyl‐β‐cyclodextrin and its Supramolecular Properties

A synthetic model glycoprotein was successfully synthesized using gelatin and mono‐6‐para‐toluenesulfonyl‐β‐cyclodextrin which were reacted under microwave conditions in basic media. The resulting glycoprotein is observed to form intermolecular inclusion complexes through complexation of the aromatic moieties along the polymer chain by the attached cyclodextrins. This phenomenon was analyzed and proven by 2D NMR spectroscopy (ROESY) and dynamic light scattering (DLS). Above the denaturation temperature, a strong increase of the hydrodynamic diameter was found due to enhanced supramolecular agglomeration. Such a novel glycoprotein with supramolecular self‐recognition would be promising in biomedical applications serving as a drug‐delivery basis polymer.

     

A convenient synthesis of 5-(1,2,4-oxadiazol-5-yl)pyrimidine-2,4(1H,3H)-diones

The synthesis of 5-heteroaryl-substituted uracil derivatives is presented. The 1,3-dipolar cycloaddition reaction was applied for the construction of a heterocyclic ring. The nitrile oxides were obtained from the appropriate 4-substituted benzaldoximes using N-chlorosuccinimide (NCS) under basic conditions. [2+3] Cycloaddition of nitrile oxides with 5-cyanouracil as a dipolarophile gave the corresponding 5-(3-substituited-1,2,4-oxadiazol-5-yl)uracils in satisfactory yields under mild conditions. 5-Substituted uracils having an additional heterocyclic ring were obtained as a result of the [2+3] cycloaddition of 5-cyanouracil to nitrile oxides generated from thiophene-2-carbaldehyde and 5-formyluracil derivatives.     

Enthalpies of mixing of liquid systems for lead-free soldering: Cu–Sb–Sn system

Using two different types of high temperature drop calorimeters, partial and integral enthalpies of mixing of liquid alloys were determined in the ternary Cu–Sb–Sn system. The system was investigated along four sections at 1100 K. Experimental data were used to find ternary interaction parameters by applying the Redlich–Kister–Muggianu model for substitutional solutions, and a full set of parameters describing the concentration dependence of the enthalpy of mixing was derived. From these, the isoenthalpy curves were constructed for 1100 K. The entire system shows exothermic enthalpy of mixing at the given temperature.     

Aldimines of 5-aminouracil as reagents in 1,3-dipolar cycloaddition reaction

Abstract  

The condensation of 5-aminouracil with aromatic aldehydes gave the appropriate C-arylimines, which were used in [2+3] cycloaddition with nitrile oxides derived from 4-substituted benzaldoximes. As a result of the dipolar cycloaddition reaction several hitherto unknown 5-(3,5-diphenyl-1,2,4-oxadiazol-4(5H)-yl)pyrimidine-2,4(1H,3H)-diones have been obtained in satisfactory yields.