Crystallization of 2D Hybrid Organic–Inorganic Perovskites Templated by Conductive Substrates

2D hybrid organic–inorganic perovskites are valued in optoelectronic applications for their tunable bandgap and excellent moisture and irradiation stability. These properties stem from both the chemical composition and crystallinity of the layer formed. Defects in the lattice, impurities, and crystal grain boundaries generally introduce trap states and surface energy pinning, limiting the ultimate performance of the perovskite; hence, an in-depth understanding of the crystallization process is indispensable. Here, a kinetic and thermodynamic study of 2D perovskite layer crystallization on transparent conductive substrates are provided—fluorine-doped tin oxide and graphene. Due to markedly different surface structure and chemistry, the two substrates interact differently with the perovskite layer. A time-resolved grazing-incidence wide-angle X-ray scattering (GIWAXS) is used to monitor the crystallization on the two substrates. Molecular dynamics simulations are employed to explain the experimental data and to rationalize the perovskite layer formation. The findings assist substrate selection based on the required film morphology, revealing the structural dynamics during the crystallization process, thus helping to tackle the technological challenges of structure formation of 2D perovskites for optoelectronic devices.     

Biosynthesis of Colabomycin E,a New Manumycin‐Family Metabolite,Involves an Unusual Chain‐Length Factor

Colabomycin E is a new member of the manumycin‐type metabolites produced by the strain Streptomyces aureus SOK1/5‐04 and identified by genetic screening from a library of streptomycete strains. The structures of colabomycin E and accompanying congeners were resolved. The entire biosynthetic gene cluster was cloned and expressed in Streptomyces lividans. Bioinformatic analysis and mutagenic studies identified components of the biosynthetic pathway that are involved in the formation of both polyketide chains. Recombinant polyketide synthases (PKSs) assembled from the components of colabomycin E and asukamycin biosynthetic routes catalyzing the biosynthesis of “lower” carbon chains were constructed and expressed in S. aureus SOK1/5‐04 ΔcolC11–14 deletion mutant. Analysis of the metabolites produced by recombinant strains provided evidence that in both biosynthetic pathways the length of the lower carbon chain is controlled by an unusual chain‐length factor supporting biosynthesis either of a triketide in asukamycin or of a tetraketide in colabomycin E. Biological activity assays indicated that colabomycin E significantly inhibited IL‐1β release from THP‐1 cells and might thus potentially act as an anti‐inflammatory agent.     

The impact of pulsed electric fields on quality parameters of freeze-dried red beets and pineapples

The effect of pulsed electric fields (PEF) on the cell disintegration index (Zp), the freeze-drying process and the final product quality of red beet and pineapple tissue was studied. Red beets and pineapples were PEF-treated at an electric field strength of 1.07 kV/cm and specific energy inputs of 1 kJ/kg and 4 kJ/kg (PEF₁ and PEF₂, respectively). Freeze-drying was performed at a pressure of 1 mbar and heating plate temperature of 50 °C for red beet and 40 °C for pineapple. The quality of freeze-dried tissue was evaluated by the analysis of residual moisture content, macrostructure, texture, colour and rehydration properties. For freeze-dried red beets, the betalain content from extracts was studied. It could be stated that PEF pre-treatment had no significant influence on drying time reduction, however significantly improved the final quality of freeze-dried product. Moreover, the effect of PEF was strongly depending on type of plant material used.     

Minimality of some group-extension-type flows in terms of eigenvalues

We use our criterion for minimality of restrictions of compact minimal abelian flows to characterize minimality of group-extensions, products and restrictions of suspensions in terms of eigenvalues. In particular, we get a new proof of a theorem of Parry about minimality of group-extensions and generalize some theorems about minimality of products and restrictions of suspensions.     

Enzyme flow microcalorimetry—a useful tool for screening of immobilized penicillin G acylase

Screening of a representative series of immobilized penicillin G acylase biocatalysts (enzyme, cells) using enzyme flow microcalorimetry is described. Immobilized penicillin G acylase biocatalysts were either prepared in the laboratory by various techniques or obtained from four commercial manufacturers. An industrial strain of Escherichia coli was entrapped in (poly)acrylamide gel or hardened calcium pectate gel. Semi-purified enzyme was immobilized in various ways—either by covalent binding to oxirane-acrylic beads or chlorotriazine bead cellulose or by entrapment in (poly)acrylamide gel. The validity of the enzyme flow microcalorimetry results was corroborated by a pH-stat method, showing enzyme flow microcalorimetry to be a suitable method for rapid screening of immobilized biocatalysts regardless of the immobilization technique, carrier type or the biocatalyst source. © 1998 Society of Chemical Industry     

Association of toxic and essential metals with atopy markers and ventilatory lung function in women and men

The association of age, smoking, alcohol, superoxide dismutase (SOD), glutathione peroxidase (GPx), blood lead (BPb) and cadmium (BCd) levels, and serum levels of copper (SCu), zinc (SZn) and selenium (SSe) with atopic status and ventilatory function was examined in the groups of 166 women and 50 men with no occupational exposure to metals or other xenobiotics. Markers of atopy included serum total IgE, skin prick test (SPT) to common inhalatory allergens, non-specific nasal reactivity (NNR) and non-specific bronchial reactivity (NBR). Parameters of ventilatory function included forced vital capacity (FVC) and forced expiratory volume in the first second (FEV(1)). Significantly higher BPb, SZn, IgE and prevalence of positive SPT, and lower SCu and NNR was found in men than in women. Fifteen women taking female sex hormones (HT) had significantly higher SCu than women without HT. Regression models showed significant inverse associations between IgE and SCu (P=0.021) and NNR and SCu (P=0.044) in women. When excluding women with HT, the association of SCu and total IgE became of borderline significance (P=0.051), association between SCu and NNR disappeared, and significant positive association between total IgE and BPb emerged (P=0.046). In men, significant inverse association was found between positive SPT and SSe, and between NBR and SSe. A decrease in FVC% and FEV(1)% was associated with an increase in smoking intensity (P<0.001) and a decrease in SZn (P=0.043 and P=0.053, respectively). These results were observed at the levels of the metals comparable to those in general populations worldwide. The observed differences between men and women may partly be explained by different levels of relevant toxic and essential metals, and their combination. The role of female HT in associations of atopy markers and SCu should be further investigated.