Biochemical activities of Brochothrix thermosphacta

Activities of 19 hydrolases were estimated in cell suspensions of 40 Brochothrix thermosphacta strains, isolated from meat and meat products packaged under various conditions, by using API ZYM® test. These strains produced: acidic phosphatase, esterase C4, esterase/lipase C8, α-chymotrypsin, leucine arylamidase, β-glucosidase and α-glucosidase. The predominating biotype produced only the first four of the listed enzymes. The extracellular lipolytic activity for bromo-chloro-indolyl-caprylate was detected only in culture broth supernatants of 4 strains thereby indicating that esterase/lipase C8 is cell-bound. 13 of the strains displayed proteolytic activity for albumin at 4 °C (0.31-2.07 U) while 9 strains showed this activity at 25 °C (0.11-1.21 U). Only 4 strains digested albumin at both temperatures. Thus the meat spoilage potential of B. thermosphacta strains results not only from digestion of carbohydrates but also from their proteolytic activity.     

Synthesis and dielectric investigations of ZnTiO3 obtained by a soft chemistry route

In this paper, we report a strategy for preparing an inorganic zinc titanate precursor by applying a chemical bath deposition method (CBD) to ZnO nanocrystals in an aqueous layered titanate colloid. The zinc titanate precursor, obtained as a precipitate, undergoes profound changes under the influence of elevated temperatures in normal atmospheric conditions and allows us to obtain zinc titanate ZnTiO₃ with a rhombohedral symmetry. Investigations of its dielectric properties enabled us to determine a dielectric permittivity (?) of 25, a low loss factor tan(δ) < 10⁻³, and a temperature coefficient (τ_?) of 18 ppm at the frequency of 1.15 MHz. The density of the zinc titanate ceramic was equal to approximately 80% of the theoretical density of the ZnTiO₃ crystals.     

The synthesis of novel,visible-wavelength,oxidizable polymerization sensitizers based on the 8-halogeno-5,12-dihydroquinoxalino[2,3-b]quinoxaline skeleton

Novel dyes, based on the 8-halogeno-5,12-dihydroquinoxalino[2,3-b]quinoxaline skeleton, were synthesized and characterized using ¹H NMR spectroscopy and chemical ionization mass spectroscopy. Their electrochemical and spectral properties, such as absorption and emission spectra, quantum yield of fluorescence and quantum yield of singlet oxygen generation, were also measured. These dyes were used as oxidizable sensitizers for diphenyliodonium and N-alkoxypyridinium salts. Photoredox pairs, consisting of dyes and pyridinium or iodonium salts, were found to be effective visible-wavelength initiators of free radical or cationic polymerization, respectively. The ability of each dye to act as a photoinitiator strongly depended upon its chemical structure. The heavy atoms present in the chemical structure could lead to excited triplet states within the dye, thereby facilitating electron transfer from these states.     

Chromophore of an Enhanced Green Fluorescent Protein Can Play a Photoprotective Role Due to Photobleaching

Under stress conditions, elevated levels of cellular reactive oxygen species (ROS) may impair crucial cellular structures. To counteract the resulting oxidative damage, living cells are equipped with several defense mechanisms, including photoprotective functions of specific proteins. Here, we discuss the plausible ROS scavenging mechanisms by the enhanced green fluorescent protein, EGFP. To check if this protein could fulfill a photoprotective function, we employed electron spin resonance (ESR) in combination with spin-trapping. Two organic photosensitizers, rose bengal and methylene blue, as well as an inorganic photocatalyst, nano-TiO₂, were used to photogenerate ROS. Spin-traps, TMP-OH and DMPO, and a nitroxide radical, TEMPOL, served as molecular targets for ROS. Our results show that EGFP quenches various forms of ROS, including superoxide radicals and singlet oxygen. Compared to the three proteins PNP, papain, and BSA, EGFP revealed high ROS quenching ability, which suggests its photoprotective role in living systems. Damage to the EGFP chromophore was also observed under strong photo-oxidative conditions. This study contributes to the discussion on the protective function of fluorescent proteins homologous to the green fluorescent protein (GFP). It also draws attention to the possible interactions of GFP-like proteins with ROS in systems where such proteins are used as biological markers.     

PGS/HAp Microporous Composite Scaffold Obtained in the TIPS-TCL-SL Method: An Innovation for Bone Tissue Engineering

In this research, we synthesize and characterize poly(glycerol sebacate) pre-polymer (pPGS) (¹H NMR, FTiR, GPC, and TGA). Nano-hydroxyapatite (HAp) is synthesized using the wet precipitation method. Next, the materials are used to prepare a PGS-based composite with a 25 wt.% addition of HAp. Microporous composites are formed by means of thermally induced phase separation (TIPS) followed by thermal cross-linking (TCL) and salt leaching (SL). The manufactured microporous materials (PGS and PGS/HAp) are then subjected to imaging by means of SEM and µCT for the porous structure characterization. DSC, TGA, and water contact angle measurements are used for further evaluation of the materials. To assess the cytocompatibility and biological potential of PGS-based composites, preosteoblasts and differentiated hFOB 1.19 osteoblasts are employed as in vitro models. Apart from the cytocompatibility, the scaffolds supported cell adhesion and were readily populated by the hFOB1.19 preosteoblasts. HAp-facilitated scaffolds displayed osteoconductive properties, supporting the terminal differentiation of osteoblasts as indicated by the production of alkaline phosphatase, osteocalcin and osteopontin. Notably, the PGS/HAp scaffolds induced the production of significant amounts of osteoclastogenic cytokines: IL-1β, IL-6 and TNF-α, which induced scaffold remodeling and promoted the reconstruction of bone tissue. Initial biocompatibility tests showed no signs of adverse effects of PGS-based scaffolds toward adult BALB/c mice.     

The Significance of the DUF283 Domain for the Activity of Human Ribonuclease Dicer

Dicers are multidomain proteins, usually comprising an amino-terminal putative helicase domain, a DUF283 domain (domain of unknown function), a PAZ domain, two RNase III domains (RNase IIIa and RNase IIIb) and a dsRNA-binding domain. Dicer homologs play an important role in the biogenesis of small regulatory RNAs by cleaving single-stranded precursors adopting stem-loop structures (pre-miRNAs) and double-strand RNAs into short RNA duplexes containing functional microRNAs or small interfering RNAs, respectively. Growing evidence shows that apart from the canonical role, Dicer proteins can serve a number of other functions. For example, results of our previous studies showed that human Dicer (hDicer), presumably through its DUF283 domain, can facilitate hybridization between two complementary RNAs, thus, acting as a nucleic acid annealer. Here, to test this assumption, we prepared a hDicer deletion variant lacking the amino acid residues 625-752 corresponding to the DUF283 domain. The respective 128-amino acid fragment of hDicer was earlier demonstrated to accelerate base-pairing between two complementary RNAs in vitro. We show that the ΔDUF(625-752) hDicer variant loses the potential to facilitate RNA-RNA base pairing, which strongly proves our hypothesis about the importance of the DUF283 domain for the RNA-RNA annealing activity of hDicer. Interestingly, the in vitro biochemical characterization of the obtained deletion variant reveals that it displays different RNA cleavage properties depending on the pre-miRNA substrate.     

Liquid-crystalline phases formed by symmetrical azines with different terminal chains: Thermal,optical and electrical study

One series of symmetrical azine-type liquid crystals were synthesized and their chemical structure identified by FTIR, NMR, high resolution mass spectrometry-electro spray ionization (MS-ESI) and elemental analysis. The absorption (UV–vis), photoluminescence (PL) and thermoluminescence (TL) features of the compounds are documented. X-ray diffraction was employed to evaluate their phase transitional behaviour. Their mesomorphic properties were investigated by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). Terminal groups of the liquid crystals had an effect on their mesomorphic properties. Azine with alkoxysemiperfluorinated end-groups (A1) exhibited smectic C (SmC) phase, whereas azine with octadecyloxy end chains (A3) showed SmC and SmA phases. Azine with 5″-octyl-2,2′:5′,2″-terthiophene groups (A2) exhibited only nematic phase. Different types of N and SmC textures were found and investigated by POM technique. Azine with thiophene groups (A2) has an absorption band about 138 nm batochromically shifted compared to the analogous band of other compounds. The lowest optical band gap value (2.34 eV) was detected for A2. Azines emitted violet or green light. The thermoluminescence emission of azines occurred at about 390–440 nm wavelengths. Current–voltage measurements were performed on ITO/compound/Alq₃/Al and ITO/TiO₂/compound/Alq₃/Al devices before and after light irradiation. To prepare TiO₂ layer, sol–gel technique was applied.     

Determination of free radicals and flavan-3-ols content in fermented and unfermented teas and properties of their infusions

The objective of this study was to analyse selected brands of fermented (red and black) and unfermented (white and green) teas for free radical content with the use of electron paramagnetic resonance (EPR) spectroscopy and for contents of flavan-3-ols by means of high-performance liquid chromatography. Analyses were also conducted for the polyphenolic profile of infusions of the analysed teas (with the Folin–Ciocalteu’s method) and their antioxidant activity (in reaction with a DPPH radical) at three brewing times (5, 10 and 15 min). The obtained results showed the possibility of using rapid spectroscopic method EPR to evaluate the oxidative changes in tea leaves caused by enzymatic fermentation. The number of free radicals in teas was negatively correlated with contents of flavan-3-ols, (?)-EGCG in particular. The main signals observed in EPR spectra of teas were attributed to semiquinone radicals; however, also signals attributed to carbohydrate radicals were detected. Regarding unfermented teas, it was ascertained that teas with the highest content of flavan-3-ols, (?)-EGCG in particular, were characterised by the lowest content of semiquinone radicals and a high content of carbohydrate radicals. The group of fermented teas demonstrated to contain mainly semiquinone radicals. The total phenolic content and antioxidant activity of the tea infusions were strongly diversified depending on the kind and brand of tea as well as on the extraction time. The predominating flavan-3-ol in the analysed teas was epigallocatechin gallate (?)-EGCG, the content of which was additionally highly correlated with the antioxidant activity of the tea infusions.     

A study of thermal,optical and electrical properties of new branched triphenylamine-based polyazomethines

A series of branched aromatic polyazomethines have been obtained by high temperature solution polycondensation of 4,4′,4″-triformyltriphenylamine with 3,3′-dimethoxybenzidine with different feed molar ratio. For three polymers additional condensation of chain end groups with monofunctional monomers such as 4-formyltriphenylamine or 2-naphthylamine was carried out. Moreover, two model compounds were prepared and investigated for comparison with branched polymers. The structures of polymers and models were characterized by means FTIR, ¹H, ¹³C NMR spectroscopy, elemental analysis and gel permeation chromatography (GPC). UV–vis properties of the thin films of the polymers and compounds were investigated on the glass substrate. Eg of the branched polymers was found about 2.47 eV. UV–vis and FTIR spectroscopy for iodine doped compounds were investigated. Doping decreased the value of Eg of the branched polyazomethines to about 1.71 eV. Refractive index (n) for branched polyazomethines was found about 1.97, while for the doped compounds was a little higher (～2.48). Absorption (UV–vis) properties of the doped with iodine branched imines were investigated additionally after heating in different temperatures from 50 to 200 °C. Intensity of photoluminescence of branched imines in relation to 9,10-diphenylanthracene was found in the range 0.2–1.0% and 2.7–43.7% in dependence on the excitation wavelengths. Current–voltage (I–V) measurements were performed on ITO/TiO₂/polymer/Al, ITO/polymer/Alq₃/Al and ITO/TiO₂/polymer/Alq₃/Al devices in the dark and during irradiation with light (under illumination 1000 W/m²). The sol–gel technique was applied to prepared TiO₂ layer. TiO₂ layers and devices were investigated by Atomic Force Microscopy (AFM). Moreover, properties of these branched polymers were compared with the linear polyazomethine based on 3,3′-dimethoxybenzidine and 4,4′-diformyltriphenylamine.     

Pressureless sintering of single-phase tantalum carbide and niobium carbide

This work presents the results of studies on the preparation of single-phase polycrystalline tantalum carbide and niobium carbide. It has been found that it is possible to obtain polycrystals with high density in the pressureless sintering process at temperatures up to 2000 °C and therefore relatively low temperatures such as for the compounds with one of the highest melting points; TaC – 3985 °C and NbC – 3600 °C. Only carbon as a sintering additive was used. The main role of carbon is to reduce of oxide contamination. It has been shown that the determination of the amount of carbon required to reduce oxide contamination is only possible through the experimental method.