Influence of Polymer Solvents on the Properties of Halloysite-Modified Polyethersulfone Membranes Prepared by Wet Phase Inversion

Ultrafiltration polyethersulfone (PES) membranes were prepared by wet phase inversion. Commercial halloysite nanotubes (HNTs) in the quantities of 0.5 wt% vs. PES (15 wt%) were introduced into the casting solution containing the polymer and different solvents: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), or 1-methyl-2-pyrrolidinone (NMP). The type of solvent influenced the membranes’ morphology and topography, as well as permeability, separation characteristics, and antifouling and antibacterial properties. The membranes prepared using DMA exhibited the loosest cross-section structure with the thinnest skin and the roughest surface, while the densest and smoothest were the DMF-based membranes. The advanced contact angles were visibly lower in the case of the membranes prepared using DMF compared to the other solvents. The highest water permeability was observed for the DMA-based membranes, however, the most significant effect of the modification with HNTs was found for the NMP-based series. Regardless of the solvent, the introduction of HNTs resulted in an improvement of the separation properties of membranes. A noticeable enhancement of antifouling performance upon application of HNTs was found only in the case of DMF-based membranes. The study of the antibacterial properties showed that the increase in surface roughness had a positive effect on the inhibition of E. coli growth.     

Effect of Grinding Process Parameters and Storage Time on Extraction of Antioxidants from Ginger and Nutmeg

The aim of this study was to optimize the grinding process parameters (mesh size of grinder sieve (X₁), the peripheral velocity of the grinding wheels (X₂)), and the storage time (X₃) of ground ginger rhizome and nutmeg to obtain ethanol and ethanol-water extracts with improved antioxidant properties. The optimal conditions were estimated using response surface methodology (RSM) based on a three-variable Box–Behnken design (BBD) in order to maximize the antioxidant capacity (AC) determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods, and the total phenolic content (TPC) was determined by the Folin–Ciocalteu (F–C) method in spice extracts. Additionally, the phenolic acid profiles in extracts from optimized conditions were analyzed using ultra-performance liquid chromatography (UPLC). It was found that the optimal preparation conditions for antioxidant extraction were dependent on the spice source and solvent type. The best antioxidant properties in nutmeg extracts were achieved for X₁ = 1.0 mm, X₂ = 40–41 Hz and X₃ = 7 days, whereas the optimized parameters for ginger extracts were more varied (1.0–2.0 mm, 43–50 Hz and 1–9 days, respectively). The ginger extracts contained 1.5–1.8 times more phenolic acids, and vanillic, ferulic, gallic, and p-OH-benzoic acids were dominant. In contrast, the nutmeg extracts were rich in protocatechuic, vanillic, and ferulic acids.     

Molecular Imaging of Biological Samples on Nanophotonic Laser Desorption Ionization Platforms

Mass spectrometry imaging (MSI) is a comprehensive tool for the analysis of a wide range of biomolecules. The mainstream method for molecular MSI is matrix‐assisted laser desorption ionization, however, the presence of a matrix results in spectral interferences and the suppression of some analyte ions. Herein we demonstrate a new matrix‐free MSI technique using nanophotonic ionization based on laser desorption ionization (LDI) from a highly uniform silicon nanopost array (NAPA). In mouse brain and kidney tissue sections, the distributions of over 80 putatively annotated molecular species are determined with 40 μm spatial resolution. Furthermore, NAPA‐LDI‐MS is used to selectively analyze metabolites and lipids from sparsely distributed algal cells and the lamellipodia of human hepatocytes. Our results open the door for matrix‐free MSI of tissue sections and small cell populations by nanophotonic ionization.     

Calorimetric detection of the toxic effect of androgens on fission yeast

Calorimetry is evaluated for study of the toxic effect of environmental androgens on Schizosaccharomyces pombe cells. The results indicate that androstendione, androstandiendione and dehydrotestosterone inhibited S. pombe heat production rate. Although, the turbidimetric method showed that testosterone (TS) had no influence on growth of S. pombe, calorimetry revealed that there was a shift in growth period in samples with TS.     

Novel Aspects of a Convenient Synthesis and of Electroproperties of Derivatives Based on Diphenylamine

The substituted monomers 4a , c , d, 5a , b, 6a, 7a , b , and 8a of novel poly(diphenylamines), possessing the respective photochromic groups, were synthesized by the Stille cross‐coupling methodology (Scheme). The hyperbranched structures were characterized by ¹H‐ and ¹³C‐NMR spectroscopy. The obtained monomers show good stability in common organic solvents such as CHCl₃, toluene, and CH₂Cl₂, and exhibit excellent thermal stability. Electrochemical results and theoretical calculations suggest that oxidation and reduction of the monomers start from the side of the amine function and the five‐membered heterocyclic ring moieties, respectively.     

Planarity of benzoyldithiocarbazate tuberculostatics. II. Diesters of benzoyldithiocarbazic acid

The emergence of drug‐resistant strains of Mycobacterium tuberculosis has intensified efforts to identify new lead tuberculostatics. Our earlier studies concluded that the planarity of a molecule correlates well with its tuberculostatic activity. According to our hypothesis, only derivatives whose molecules are capable of adopting a planar conformation may show tuberculostatic activity. The structures of three new potentially tuberculostatic compounds, namely N′‐[bis(methylsulfanyl)methylidene]‐N‐methyl‐4‐nitrobenzohydrazide (denoted G1), C₁₁H₁₃N₃O₃S₂, N′‐[bis(benzylsulfanyl)methylidene]‐N‐methyl‐4‐nitrobenzohydrazide (denoted G2), C₂₃H₂₁N₃O₃S₂, and N′‐[(benzylsulfanyl)(methylsulfanyl)methylidene]‐4‐nitrobenzohydrazide (denoted G3), C₁₆H₁₅N₃O₃S₂, were determined by X‐ray diffraction. The significant distortion from planarity caused by the methyl substituent at the N atom of the hydrazide group or the NO₂ substituent in the aromatic ring leads to the loss of tuberculostatic activity for G1, G2 and G4 {systematic name: N′‐[bis(methylsulfanyl)methylidene]‐2‐nitrobenzohydrazide}. A similar effect is observed when there are large substituents at the S atoms (G2 and G3).     

Voltammetric Determination of an Anti-rheumatoid Drug Acemetacin on Graphite Flake Paste Electrode and Glassy Carbon Electrode

In this study, a simple and sensitive square wave voltammetric procedure has been developed for the determination of acemetacin (ACM) at graphite flake paste electrode (GFPE) and glassy carbon electrode (GCE). Under optimized conditions, the dependence of ACM peak current on its concentration showed wide linear range: 0.03–1.0 μmol L⁻¹ and 0.7–15.0 μmol L⁻¹ at GFPE and GCE, respectively. The developed method was successfully applied for the determination of ACM in pharmaceuticals and spiked urine with satisfying recoveries. The electrochemical oxidation of ACM is an irreversible process controlled by mixed nature of the mass transfer process.     

A Comparison of Edge-plane and Basal-plane Pyrolytic Graphite Electrodes towards Sensitive Determination of the Fungicide Mandipropamid

A sensitive square-wave voltammetry (SWV) method based on basal-plane pyrolytic graphite electrode (BPPGE) and edge-plane pyrolytic graphite electrode (EPPGE) was developed to determine the concentration of the pesticide mandipropamid (MAN) in spiked river water and grape juice samples. Under optimal experimental conditions, the SWV response of EPPGE and BPPGE was linear over the concentration ranges of 0.7 to 9.0 μmol L⁻¹ and 0.5 to 10.0 μmol L⁻¹, respectively. The method was successfully used to determine MAN in spiked samples with good recovery. Cyclic voltammetry (CV) was conducted to understand the mechanism underlying the electrode process of MAN.     

Spectral Gap of Segments of Periodic Waveguides

The lowest spectral gap of segments of a periodic waveguide in is proportional to the square of the inverse length. Dedicated to Pavel Exner on the occasion of his 60th birthday.