Supramolecular Polymers: Rigid Dimers Formed through Strong Interdigitated H‐Bonds Yield Compact 1D Supramolecular Helical Polymers (Small 3/2011)

Hierarchical self‐assembly of small abiotic molecular modules interacting through noncovalent forces is increasingly being used to generate functional structures and materials for electronic, catalytic, and biomedical applications. The greatest control over the geometry in H‐bond supramolecular architectures, especially in H‐bonded supramolecular polymers, can be achieved by using conformationally rigid molecular modules undergoing self‐assembly through strong H‐bonds. Their binding strength depends on the multiplicity of the H‐bonds, the nature of donor/acceptor pairs and their secondary attractive/repulsive interactions. Here a functionalized molecular module is described, which is capable of self‐associating through self‐complementary H‐bonding patterns comprising four strong and two medium‐strength H‐bonds to form dimers. The self‐association of these phenylpyrimidine‐based dimers through directional H‐bonding between two lateral pyridin‐2(1H)‐one units of neighboring molecules allows the formation of highly compact 1D supramolecular polymers by self‐assembly on graphite. A concentration‐dependent study by scanning tunneling microscopy at the solid–liquid interface, corroborated by dispersion‐corrected density functional studies, reveals the controlled generation of either linear supramolecular 2D arrays, or long helical supramolecular polymers with a high shape persistence.     

Behavior of Yersinia enterocolitica strains inoculated in model cheese treated with high hydrostatic pressure

The effects of high hydrostatic pressure treatment and the ability for survival, repair, and growth of three human pathogenic serotypes (O:1, O:3, O:8) of Yersinia enterocolitica were investigated in washed-curd model cheese made with pasteurized bovine milk. Samples were treated at 300, 400, and 500 MPa for 10 min at 20 degrees C and analyzed at 0, 1, 7, and 15 days to assess the viability of the Yersinia population. A long-term study (up to 60 days of ripening after high hydrostatic pressure treatment) was also undertaken. Treatments at 400 and 500 MPa caused maximum lethality, and only the treatment at 300 MPa showed significant differences (P < 0.05) between serotypes; the most baroresistant was O:3. Ability to repair and grow was not observed after 15 days of storage at 8 degrees C. Yersinia counts in untreated cheese samples also decreased below the detection limit at day 45 in the long-term study. These results suggest that the cheese environment did not allow recovery of injured cells or growth. A primary contributing factor to this effect seemed to be the low pH resulting from the production of lactic acid during cheese ripening.     

Improved performance of the ultrafiltration membranes by simple modification with air plasma treatment and polymeric deposition

This study seeks to increase the antifouling properties of fluorinated polyvinylidene (PVDF) membranes through the synergistic application of plasma treatment and polymer deposition, employing polymerizations of polyvinylpyrrolidone (PVP) and polyethyleneimine (PEI). The results show remarkable success in modifications, presenting exceptional performance. Two distinct surface modification methods, plasma treatment and polymer deposition, were used to improve the antifouling properties and filtration performance of PVDF membranes. The plasma used was a discharge dielectric barrier using ambient air as gas, and hydrophilic polymers, PVP, and PEI. The results outlined changes in membrane roughness with a significant roughness reduction of up to 43% evident based on topographic and morphological analyses. Hydraulic permeability analysis revealed a substantial 35-fold increase, indicating a notable improvement in performance. All treated membranes exhibited higher water affinity and superior performance during 12-h ultrafiltration compared to their untreated counterparts. After chemical cleaning, water flux recovery exceeded 85% for all treated membranes, indicating the inherent antifouling properties of the surface.     

Biodegradability evaluation of wastewaters from malt and beer production

This study reports results of respirometric measurements of activated sludge biodegrading the substrate in wastewater originating from the following brewery plant production departments: malt house, brewhouse, fermentation house and racking house. The process was conducted at two temperatures: 10 and 20°C with activated sludge adapted to brewery wastewaters. The loading of activated sludge reached 0.25 g chemical oxygen demand per gram dry matter per day, which assured complete degradation of organic matter. The physicochemical characteristics of the wastewaters are provided. The study demonstrates a correlation between the site of wastewater generation, the specific character of a unitary technological process and the quality of the wastewater discharged to the sewage system, including biodegradability. Despite significant differences in the quality of the wastewaters, they were characterized by high biodegradability at a temperature of 10 and 20°C and by the C:N:P ratio being beneficial for biological treatment, irrespective of their source of origin. Copyright © 2013 The Institute of Brewing & Distilling     

Impact of Porcine Pancreas Decellularization Conditions on the Quality of Obtained dECM

Due to the limited number of organ donors, 3D printing of organs is a promising technique. Tissue engineering is increasingly using xenogeneic material for this purpose. This study was aimed at assessing the safety of decellularized porcine pancreas, together with the analysis of the risk of an undesirable immune response. We tested eight variants of the decellularization process. We determined the following impacts: rinsing agents (PBS/NH₃·H₂O), temperature conditions (4 °C/24 °C), and the grinding method of native material (ground/cut). To assess the quality of the extracellular matrix after the completed decellularization process, analyses of the following were performed: DNA concentration, fat content, microscopic evaluation, proteolysis, material cytotoxicity, and most importantly, the Triton X-100 content. Our analyses showed that we obtained a product with an extremely low detergent content with negligible residual DNA content. The obtained results confirmed the performed histological and immuno-fluorescence staining. Moreover, the TEM microscopic analysis proved that the correct collagen structure was preserved after the decellularization process. Based on the obtained results, we chose the most favorable variant in terms of quality and biology. The method we chose is an effective and safe method that gives a chance for the development of transplant and regenerative medicine.     

3‐Chlorooxindoles: Versatile Starting Materials for Asymmetric Organocatalytic Synthesis of Spirooxindoles

3‐Chlorooxoindoles have emerged as versatile precursors in the synthesis of spirocyclopropyl oxindoles. High enantio‐ and diastereoselectivity was attained under conditions of both iminium/enamine and H‐bonding catalysis.     

Atomically Precise Prediction of 2D Self‐Assembly of Weakly Bonded Nanostructures: STM Insight into Concentration‐Dependent Architectures

A joint experimental and computational study is reported on the concentration‐dependant self‐assembly of a flat C₃‐symmetric molecule on a graphite surface. As a model system a tripodal molecule, 1,3,5‐tris(pyridin‐3‐ylethynyl)benzene, has been chosen, which can adopt either C_3h or C_s symmetry when planar, as a result of pyridyl rotation along the alkynyl spacers. Density functional theory (DFT) simulations of 2D nanopatterns with different surface coverage reveal that the molecule can generate different types of self‐assembled motifs. The stability of fourteen 2D patterns and the influence of concentration are analyzed. It is found that ordered, densely packed monolayers and 2D porous networks are obtained at high and low concentrations, respectively. A concentration‐dependent scanning tunneling microscopy (STM) investigation of this molecular self‐assembly system at a solution/graphite interface reveals four supramolecular motifs, which are in perfect agreement with those predicted by simulations. Therefore, this DFT method represents a key step forward toward the atomically precise prediction of molecular self‐assembly on surfaces and at interfaces.     

Influence of repeller potential on ion-molecule reactions in methane and carbon tetrafluoride mixtures

Investigations of ion-molecule reactions were performed for methane-carbon tetrafluoride mixtures of different compositions. Concentration of methane in these mixtures ranged from 10% to 90% (at 10% increment) and total mixture pressure was fixed at 13.3 Pa. Measurements were made using a quadrupole mass spectrometer with a high-pressure ion source. Primary ions CH₄⁺, F⁺, CF⁺ and CF₃⁺ were produced by electrons with energy of 300 eV. Secondary ions CH₅⁺, C₂H₃⁺, C₂H₄⁺, C₂H₅⁺, C₂H₇⁺ and CF₃⁺ were observed as the result of ion-molecule reactions.The influence of repeller potential on ion-molecule reactions efficiency was examined.