Kinetic-photometric monitoring of the formation of MnO<Subscript>2</Subscript> nanoparticles and their application to the determination of iodide

We describe a method for kinetic-spectrophotometric monitoring of the formation of MnO₂ nanoparticles (NPs) by reduction of permanganate ion. Iodide was selected as a model analyte. The NPs were characterized by atomic force microscopy, transmission electron microscopy, powder x-ray diffraction, energy-dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy and nitrogen physisorption surface area analysis. The change in absorbance at 415 nm over time serves as the analytical signal, and experimental variables that affect the slope have been studied. The slope is linearly related to iodide concentrations in the range from 0.2 to 3 μg?mL￣¹, and the limits of detection and quantification are 0.05 and 0.17 μg?mL￣¹, respectively. The intraday and interday precision (given as relative standard deviations for n = 5) are 1.4 and 3 %, respectively. The method has been successfully applied to the determination of iodide in a pharmaceutical product. In our perception, this is the first model where the monitoring of the early stages of the formation of NPs has been exploited as analytical signal.

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Graphical abstract Kinetic-spectrophotometric monitoring of the formation of MnO₂ nanoparticles (NPs) by reduction of permanganate ion, enabling the determination of iodide.

     

Adsorption of cadmium and lead from palm oil mill effluent using bone-composite: optimisation and isotherm studies

The adsorption of Cd and Pb ions from palm oil mill effluent on a mesoporous-activated cow bone composite powder has been investigated. Adsorbent was developed from cow bones, coconut shells and zeolite. The composite examined in the present work has a BET surface area of 248.398 m²/g. The optimisation of the removal efficiency of the heavy metals was investigated using central composite design and analysed using response surface methodology. The analysis of variance of the quadratic model signified that the model suitably predicted the uptake of the heavy metal ions at a 95% confidence level. The optimal operating condition was recorded at pH 4, 50 rpm, within 24 h and 1 mm of particle size and 12.5 gL^?1 of adsorbent dosage. The characteristics of the composite were investigated using the Fourier transform irradiation. The morphology and chemical composition of composite was examined using the scanning electron microscopy equipped with energy dispersive x-ray. Characterisation study was conducted before and after the adsorption process. The results obtained illustrated that the removal of cadmium and lead from POME was influenced by the functional groups available on the surface of the composite. The carboxyl and hydroxyl groups are mainly responsible for the removal of cadmium and lead through chelating process. The point of zero charge (pH_pzc) revealed that the adsorbent contained acidic sites with negatively charge surface which influenced the adsorption process. The experimental data of the heavy metals of Cd and Pb investigated were fitted to the Langmuir and Freundlich models. The result revealed that the adsorption equilibrium data fitted better to the Langmuir model for the adsorption Cd and to the Freundlich model for the adsorption of Pb.     

Bis-Thiourea Bearing Aryl and Amino Acids Side Chains and Their Antibacterial Activities

Abstract

A series of symmetrical 1,3-bis thiourea 1a–e and 1,4-bis thiourea derivatives 2a–e have been successfully synthesized from the reactions of amines with 3-acetylbenzoyl isothiocyanate and 4-acetylbenzoyl isothiocyanate, respectively. All the synthesized compounds were characterized by FT-IR spectroscopy and ¹H and ¹³C NMR spectroscopy. The compounds were screened for their antibacterial activity by turbidimetric method using gram-negative bacteria (E. coli ATCC 8739) using turbidimetric method. The newly synthesized bis-thiourea derivatives bearing aryl side chains showed good antibacterial activity against E. coli. The effect of the molecular structure of the synthesized compounds on the antibacterial activity is discussed.     

Novel Copolymers of Styrene. 2. Oxy Ring-Substituted Butyl 2-Cyano-3-Phenyl-2-Propenoates

Novel trisubstituted ethylenes, oxy ring-substituted butyl 2-cyano-3-phenyl-2-propenoates, RPhCH=C(CN)CO₂C₄H₉ (where R is 2-methoxy, 3-methoxy, 4-methoxy, 2-ethoxy, 3-ethoxy, 4-ethoxy, 4-propoxy, 4-butoxy, 4-hexyloxy, 3-phenoxy) were prepared and copolymerized with styrene. The monomers were synthesized by the piperidine catalyzed Knoevenagel condensation of oxy ring-substituted benzaldehydes and butyl cyanoacetate and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. All the ethylenes were copolymerized with styrene (M₁) in solution with radical initiation (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H and ¹³C-NMR, GPC, DSC, and TGA. The order of relative reactivity (1/r₁) for the monomers is 4-methoxy (6.56) > 3-methoxy (2.97) > 2-methoxy (2.72) > 4-butoxy (2.20) > 3-ethoxy (2.18) > 4-propoxy (2.15) > 4-hexyloxy (1.78) > 4-ethoxy (1.66) > 2-ethoxy (1.48) > 3-phenoxy (1.29). Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200-500°C range with residue (0.8–3.6% wt.), which then decomposed in the 500–800°C range.     

Controlled‐Potential Electromechanical Reshaping of Cartilage

An alternative to conventional “cut‐and‐sew” cartilage surgery, electromechanical reshaping (EMR) is a molecular‐based modality in which an array of needle electrodes is inserted into cartilage held under mechanical deformation by a jig. Brief (ca. 2 min) application of an electrochemical potential at the water‐oxidation limit results in permanent reshaping of the specimen. Highly sulfated glycosaminoglycans within the cartilage matrix provide structural rigidity to the tissue through extensive ionic‐bonding networks; this matrix is highly permselective for cations. Our studies indicate that EMR results from electrochemical generation of localized, low‐pH gradients within the tissue: fixed negative charges in the proteoglycan matrix are protonated, resulting in chemically induced stress relaxation of the tissue. Re‐equilibration to physiological pH restores the fixed negative charges, and yields remodeled cartilage that retains a new shape approximated by the geometry of the reshaping jig.     

New strategy to identify radicals in a time evolving EPR data set by multivariate curve resolution-alternating least squares

Electron paramagnetic resonance (EPR) spectroscopy is a powerful technique that is able to characterize radicals formed in kinetic reactions. However, spectral characterization of individual chemical species is often limited or even unmanageable due to the severe kinetic and spectral overlap among species in kinetic processes. Therefore, we applied, for the first time, multivariate curve resolution-alternating least squares (MCR-ALS) method to EPR time evolving data sets to model and characterize the different constituents in a kinetic reaction. Here we demonstrate the advantage of multivariate analysis in the investigation of radicals formed along the kinetic process of hydroxycoumarin in alkaline medium. Multiset analysis of several EPR-monitored kinetic experiments performed in different conditions revealed the individual paramagnetic centres as well as their kinetic profiles. The results obtained by MCR-ALS method demonstrate its prominent potential in analysis of EPR time evolved spectra.     

New Potential Pharmacological Targets of Plant-Derived Hydroxyanthraquinones from Rubia spp.

The increased use of polyphenols nowadays poses the need for identification of their new pharmacological targets. Recently, structure similarity-based virtual screening of DrugBank outlined pseudopurpurin, a hydroxyanthraquinone from Rubia cordifolia spp., as similar to gatifloxacin, a synthetic antibacterial agent. This suggested the bacterial DNA gyrase and DNA topoisomerase IV as potential pharmacological targets of pseudopurpurin. In this study, estimation of structural similarity to referent antibacterial agents and molecular docking in the DNA gyrase and DNA topoisomerase IV complexes were performed for a homologous series of four hydroxyanthraquinones. Estimation of shape- and chemical feature-based similarity with (S)-gatifloxacin, a DNA gyrase inhibitor, and (S)-levofloxacin, a DNA topoisomerase IV inhibitor, outlined pseudopurpurin and munjistin as the most similar structures. The docking simulations supported the hypothesis for a plausible antibacterial activity of hydroxyanthraquinones. The predicted docking poses were grouped into 13 binding modes based on spatial similarities in the active site. The simultaneous presence of 1-OH and 3-COOH substituents in the anthraquinone scaffold were emphasized as relevant features for the binding modes’ variability and ability of the compounds to strongly bind in the DNA-enzyme complexes. The results reveal new potential pharmacological targets of the studied polyphenols and help in their prioritization as drug candidates and dietary supplements.     

Polyurethane-Based Extended Release Form of Piroxicam

Summary: The anti-inflammatory effect of piroxicam (Px) immobilized on a polyurethane (PU) matrix was studied in vivo by measuring levels of t-methylimidazole acetic acid (t-MeImAA) in urine of experimental animals. Released into body from the polymeric matrix, Px affected inflammation process, significantly reducing the t-MeImAA levels. The retention of Px within the PU/drug system – largely due to physical modification of the polymer – resulted in durable therapeutic action of the system.     

Regularity inheritance in pseudorandom graphs

Advancing the sparse regularity method, we prove one‐sided and two‐sided regularity inheritance lemmas for subgraphs of bijumbled graphs, improving on results of Conlon, Fox, and Zhao. These inheritance lemmas also imply improved H‐counting lemmas for subgraphs of bijumbled graphs, for some H.     

Modulation Effect on Tubulin Polymerization,Cytotoxicity and Antioxidant Activity of 1H-Benzimidazole-2-Yl Hydrazones

1H-benzimidazol-2-yl hydrazones with varying hydroxy and methoxy phenyl moieties were designed. Their effect on tubulin polymerization was evaluated in vitro on porcine tubulin. The compounds elongated the nucleation phase and slowed down the tubulin polymerization comparably to nocodazole. The possible binding modes of the hydrazones with tubulin were explored by molecular docking at the colchicine binding site. The anticancer activity was evaluated against human malignant cell lines MCF-7 and AR-230, as well as against normal fibroblast cells 3T3 and CCL-1. The compounds demonstrated a marked antineoplastic activity in low micromolar concentrations in both screened in vitro tumor models. The most active were the trimethoxy substituted derivative 1i and the positional isomers 1j and 1k, containing hydroxy and methoxy substituents: they showed IC₅₀ similar to the reference podophyllotoxin in both tumor cell lines, accompanied with high selectivity towards the malignantly transformed cells. The compounds exerted moderate to high ability to scavenge peroxyl radicals and certain derivatives—1l containing metha-hydroxy and para-methoxy group, and 1b-e with di/trihydroxy phenyl moiety, revealed HORAC values high or comparable to those of well-known phenolic antioxidants. Thus the 1H-benisimidazol-2-yl hydrazones with hydroxy/methoxy phenyl fragments were recognized as new agents exhibiting promising combined antioxidant and antineoplastic action.