Ultrafiltration-modified chicken egg white lysozyme and its antibacterial action

The aim of the study was to produce a lysozyme preparation with an increased content of enzyme polymeric forms using the ultrafiltration (UF) technique. The effect of selected parameters of the membrane process on the extent of enzyme modification was examined. The study showed that the membrane technique, developed for the production of lysozyme monomer, could also be used in the direct production of a preparation containing enzyme polymers. Under optimal conditions of the modification procedure, the obtained preparation contained 53.3% of lysozyme polymeric forms. The effectiveness of the antibacterial action of UF-modified lysozyme against selected strains of bacteria was determined. Its bacteriostatic activity depended on the applied modification conditions. Among lysozyme preparations modified by UF, the highest bacteriostatic activity against selected strains of bacteria was recorded in the preparation containing 53.3% polymeric forms. The modification procedure facilitates the extension of the antibacterial spectrum of lysozyme against Gram-negative bacteria ( Pseudomonas fluorescens ) .     

Novel nanomaterials based on 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-21H,23H-porphyrin entrapped in silica matrices

The present study is dealing with the obtaining of transparent hybrid silica materials encapsulating 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-21H,23H-porphyrin designated for advanced optoelectronic devices. The porphyrin was synthesized by three methods: an Adler-type reaction between pyrrole and 3,4-dimethoxybenzaldehyde in propionic acid medium; by Lindsey condensation of pyrrole with 3,4-dimethoxybenzaldehyde in the presence of BF₃·OEt₂ and by a multicomponent reaction by simultaneously using of pyrrole and two different aldehydes: 3,4-dimethoxybenzaldehyde and 3-hydroxybenzaldehyde. The 3,4-dimethoxyphenyl substituted porphyrin was characterized by HPLC, TLC, UV-vis, FT-IR, ¹H NMR and ¹³C NMR analysis. Excitation and emission spectra were also discussed in terms of pH conditions. The hybrid materials, consisting in the porphyrin encapsulated in silica matrices, have been prepared successfully via the two steps acid-base catalyzed hydrolysis and condensation of tetraethylorthosilicate using different approaches of the sol-gel process: in situ, by impregnation and by sonication. The synthetic conditions and the compositions were monitored and characterized by using spectroscopic methods such as FT-IR, fluorescence and UV-vis. Atomic force microscopy (AFM) has been applied to observe the columnar or pyramidal nanostructures which are formed by the immobilization of porphyrin on the silica matrices.     

Combined EBSD and Computer-Assisted Quantitative Analysis of the Impact of Spark Plasma Sintering Parameters on the Structure of Porous Materials

Metallurgical and Materials Transactions A - The paper presents the experimental, numerical, and theoretical investigation of the microstructure of nickel aluminide samples manufactured by spark...     

Early Postnatal Exposure to a Low Dose of Nanoparticulate Silver Induces Alterations in Glutamate Transporters in Brain of Immature Rats

Due to strong antimicrobial properties, silver nanoparticles (AgNPs) are used in a wide range of medical and consumer products, including those dedicated for infants and children. While AgNPs are known to exert neurotoxic effects, current knowledge concerning their impact on the developing brain is scarce. During investigations of mechanisms of neurotoxicity in immature rats, we studied the influence of AgNPs on glutamate transporter systems which are involved in regulation of extracellular concentration of glutamate, an excitotoxic amino acid, and compared it with positive control—Ag citrate. We identified significant deposition of AgNPs in brain tissue of exposed rats over the post-exposure time. Ultrastructural alterations in endoplasmic reticulum (ER) and Golgi complexes were observed in neurons of AgNP-exposed rats, which are characteristics of ER stress. These changes presumably underlie substantial long-lasting downregulation of neuronal glutamate transporter EAAC1, which was noted in AgNP-exposed rats. Conversely, the expression of astroglial glutamate transporters GLT-1 and GLAST was not affected by exposure to AgNPs, but the activity of the transporters was diminished. These results indicate that even low doses of AgNPs administered during an early stage of life create a substantial risk for health of immature organisms. Hence, the safety of AgNP-containing products for infants and children should be carefully considered.     

Dynamical changes during composite milling: recurrence and multiscale entropy analysis

Fluctuations describing chatter in the milling process of a composite material were analyzed using statistical, recurrence, and multiscaled entropy analyses. Through changing the rotational speed, we observed the appearance of chatter vibrations and signatures of intermittency. The corresponding characteristic change of recurrences could be used to invent a new efficient control procedure of milling. The workpiece was prepared from nonuniform material based on epoxy-polymer matrix composite reinforced by carbon fibers.     

The reuse of brine to enhance the ripening of marine and freshwater fish resistant to marinating

Cold marinades are produced mainly from the Clupeidae fish, because meat of other fish species does not reach a desired level of ripeness in the acid-salt environment of fresh brine. Hence, this work presents an innovative idea of reusing brine including cathepsins and peptides for marinating cod, salmon, trout, and carp. The extent of marinades ripening improvement depended on fish resistance to the marinating process. The reused brine proved best in improving the ripening of fatty fish (salmon and trout), which were qualified to the first class of resistance to marinating. In the case of cod, the reuse of brine did not elicit a satisfactory improvement in meat ripening. Therefore cod was qualified to the second class of resistance. The reuse of brine resulted in decreased values of lipid oxidation indices (except for cod) and meat hardness, and in increased scores for overall sensory evaluation and total volatile bases nitrogen value.     

Parameters of the epoxidation of 1-octene by t-butyl hydroperoxide

The epoxidation of 1-octene with t-butyl hydroperoxide in the presence of Mo(CO)₆ has been studied. The influence of the crucial parameters on the yield of 1,2-epoxyoctane in relation to hydroperoxide, on the hydroperoxide conversion, on the selectivity of the transformation of 1-octene to epoxy compound and on the yield of 1,2-epoxyoctane in relation to 1-octene has been described by the use of regression functions in the form of a second order polynomial. The optimal values of parameters: reaction time, temperature, olefin to hydroperoxide mol ratio, Mo(CO)₆ to hydroperoxide mol ratio, ensuring the maximum values of these functions have been determined.