Polyaniline and polypyrrole: A comparative study of the preparation

Aniline and pyrrole have been oxidized with ammonium peroxydisulfate in aqueous solutions, in the presence of equimolar quantities of hydrochloric acid. The oxidation of pyrrole was faster; the induction period typical of aniline oxidation was absent in the case of pyrrole. As the proportion of oxidant-to-monomer molar concentration increased up to 1.5, the yield increased in both cases. Similarities between the two oxidations are illustrated and discussed. The oxidant-to-monomer molar ratio 1.25 is proposed to be the optimum stoichiometry, in the accordance with the data published in the literature. The conductivities of the polymers prepared were only slightly dependent on the oxidant-to-monomer ratio in the range 0.3-1.5, and were of the order of 10⁰ S cm⁻¹ for polyaniline and ∼10⁻²-10⁻¹ S cm⁻¹ for polypyrrole. Outside this interval, the conductivity of both polymers was reduced. Polyaniline having conductivity ∼10 S cm⁻¹ was produced in solutions of phosphoric acid of various concentrations. On the contrary, the conductivity of polypyrrole was reduced as the concentration of phosphoric acid became higher. The type of protonation is discussed with the help of FTIR spectra by analyzing the ammonium salts obtained after deprotonation. Sulfate or hydrogen sulfate anions produced from peroxydisulfate always constitute a part of the counter-ions.     

Chemical Composition,Antitumor Potential,and Impact on Redox Homeostasis of the Essential Oils of Orlaya grandiflora from Two Climate Localities

It is well known that abiotic components can affect biosynthetic pathways in the production of certain volatile compounds. The aim of this study was to compare the chemical composition of essential oils obtained from Orlaya grandiflora (L.) Hoffm. collected from two localities in Serbia (continental climate, OG1) and Montenegro (Mediterranean climate, OG2) and to assess their antitumor potential on the human colon cancer HCT-116 and breast cancer MDA-MB-231 cell lines. EOs obtained by hydrodistillation were analyzed using GC-MS and GC-FID methods. The results indicate considerable differences in the chemical compositions of the two samples. Although in both samples the main class of volatiles observed was sesquiterpenes (47.5% for OG1 and 70.1% for OG2), the OG1 sample was characterized by a high amount of monoterpene hydrocarbons (29.3%), and sesquiterpene germacrene D (29.5%) as the most abundant compound. On the other hand, the OG2 sample contained a high quantity of oxygenated sesquiterpenes (20.6%), and β-elemene (22.7%) was the major constituent. The possible antitumor mechanisms of these EOs in the HCT-116 and MDA-MB-231 cell lines were examined by means of cell viability, apoptosis, redox potential, and migratory capacity. The antiviability potential appeared to be dose dependent, since the results showed that both EOs decreased the viability of the tested cells. Stronger antitumor effects were shown in MDA-MB-231 cells after short-term treatment, especially at the highest applied concentration, where the percentage of viability was reduced by over 40%. All tested concentrations of EOs exhibited proapoptotic activity and elevated activity of caspase-3 in a dose- and time-dependent manner. The results also showed decreased concentrations of superoxide anion radical in the treated cells, which indicates their significant antioxidative role. Long-term treatments showed mild recovery effects on cell viability in both cell lines, probably caused by the balancing of redox homeostasis. Elevated levels of nitrites indicate high levels of nitric oxide (NO) production and suggest its higher bioavailability due to the antioxidative environment. The tested EOs also induced a drop in migratory capacity, especially after short-time treatments. Taken together, these results suggest considerable antitumor activity of both EOs, which could have potential therapeutic applications.     

Acrylamide-Derived Ionome,Metabolic, and Cell Cycle Alterations Are Alleviated by Ascorbic Acid in the Fission Yeast

Acrylamide (AA), is a chemical with multiple industrial applications, however, it can be found in foods that are rich in carbohydrates. Due to its genotoxic and cytotoxic effects, AA has been classified as a potential carcinogen. With the use of spectrophotometry, ICP-OES, fluorescence spectroscopy, and microscopy cell growth, metabolic activity, apoptosis, ROS production, MDA formation, CAT and SOD activity, ionome balance, and chromosome segregation were determined in Schizosaccharomyces pombe. AA caused growth and metabolic activity retardation, enhanced ROS and MDA production, and modulated antioxidant enzyme activity. This led to damage to the cell homeostasis due to ionome balance disruption. Moreover, AA-induced oxidative stress caused alterations in the cell cycle regulation resulting in chromosome segregation errors, as 4.07% of cells displayed sister chromatid non-disjunction during mitosis. Ascorbic acid (AsA, Vitamin C), a strong natural antioxidant, was used to alleviate the negative impact of AA. Cell pre-treatment with AsA significantly improved AA impaired growth, and antioxidant capacity, and supported ionome balance maintenance mainly due to the promotion of calcium uptake. Chromosome missegregation was reduced to 1.79% (44% improvement) by AsA pre-incubation. Results of our multiapproach analyses suggest that AA-induced oxidative stress is the major cause of alteration to cell homeostasis and cell cycle regulation.     

Biosynthesis of Quantum Dots (CdTe) and its Effect on Eisenia fetida and Escherichia coli

Biosynthesis belongs to one of the new possibilities of nanoparticles preparation, whereas its main advantage is biocompatibility. In addition, the ability of obtaining the raw material for such synthesis from the soil environment is beneficial and could be useful for remediation. However, the knowledge of mechanisms that are necessary for the biosynthesis or effect on the bio-synthesizing organisms is still insufficient. In this study, we attempted to evaluate the effect of quantum dots (QDs) not only on a model organism of collembolans, but also on another soil organism—earthworm Eisenia fetida—and in also one widespread microorganism such as Escherichia coli. Primarily, we determined 28EC₅₀ as 72.4 μmol L^?1 for CdTe QDs in collembolans. Further, we studied the effect of QDs biosynthesis in E. fetida and E. coli. Using determination of QDs, low-molecular thiols and antioxidant activities, we found differences between both organisms and also between ways how they behave in the presence of Cd and/or Cd and Te. The biosynthesis in earthworms can be considered as its own protective mechanism; however, in E. coli, it is probably a by-product of protective mechanisms.     

Microwave Assisted Digestion Method for the Determination of Cadmium,Copper, Lead,and Zinc in Biological Materials

Anodic stripping voltammetry is useful instrumental method for trace element determination in biological materials. It is however extremely demanding to the quality of the sample preparation process. The high‐pressure microwave assisted digestion seems to meet its requirements. The differential pulse anodic stripping voltammetry technique was used for determination of cadmium, copper, lead and zinc in certified reference materials both of plant and of animal origin to prove the analytical properties of such sample preparation method. The found concentrations have been in satisfactory agreement with the certified values. The elaborated digestion procedure is greatly universal and has required accuracy and precision.     

Dynamics of gel isoelectric focusing with ampholytic dyes monitored by camera in real-time

The dynamics of gel isoelectric focusing were studied by using amphoteric low-molecular-mass colored substances (isoelectric point markers). The polyacrylamide gel in slab format was in direct contact with the electrodes. In addition to isoelectric focusing with a pH gradient composed of synthetic carrier ampholytes, pH gradients created by simple buffers of acetic acid, 2-(N-morpholino)ethanesulfonic acid, histidine and N,N,N',N'-tetramethylethylenediamine were applied. The progress of the electrofocusing process was monitored by a charge-coupled device camera and video recording. The gradient profile and dynamics were approximated from the positions of isoelectric point markers, which were focused both on boundaries between individual zones of simple buffers and within the zones themselves. The obtained animated records enabled the observation of the entire real focusing run within fractions of a minute, which is useful both for the understanding and optimization of the focusing.     

[Cu(X-salicylato)2(N,N-diethylnicotinamide)2(H2O)2] complexes: conformational polymorphism and its consequence in supramolecular hydrogen-bonding networks formation

Novel copper(II) X-salicylate complexes with N,N-diethylnicotinamide (dena) of the formula [Cu(RCOO)₂(dena)₂(H₂O)₂] (RCOO = 3-methylsalicylate anion (3-Mesal, 1), 4-methylsalicylate anion (4-Mesal, 2), 5-methylsalicylate anion (5-Mesal, 3), 5-methoxysalicylate anion (5-MeOsal, 4) or 4-methoxysalicylate anion (4-MeOsal, 5)), and complex [Cu(3-MeOsal)₂(dena)₂(H₂O)₂]∙2H₂O (3-MeOsal = 3-methoxysalicylate anion (6)) have been prepared in the crystalline forms and characterized by spectroscopic methods (IR, Vis–UV, EPR). All the compounds according to their composition (1–5) seem to possess octahedral copper(II) stereochemistry. The complex 1 has been prepared in two different forms. X-ray analyses of the complexes 1, 4, and 5 were carried out and they featured a tetragonal-bipyramidal geometry around the copper atoms. The tetragonal planes are created by X-salicylate anions bonded to the copper(II) atoms via unidentate carboxylate oxygen atoms and the pyridine ring nitrogen atoms of the neutral ligand N,N-diethylnicotinamide, while in axial positions are water molecules. The two forms of complex 1 present conformation polymorphs and supramolecular isomers.     

A diastereoselective C–C bond formation at C-5 of d-gulose. A convenient approach to (5S)-5-C-alkyl-β-l-lyxo-hexofuranoses

A flexible approach to the stereoselective synthesis of (5S)-5-C-methyl- and (5S)-5-C-ethyl-β-l-lyxo-hexofuranoses 15a, 22 starting from 1,2:5,6-di-O-isopropylidene-α-d-gulofuranose 3 as the source of chirality is described. The corresponding C-5 alkyl groups were introduced via a Wittig olefination followed by Pd/C-mediated hydrogenation of the conformationally restricted alkenes in a highly diastereoselective manner.     

Biosynthesis of Quantum Dots (CdTe) and its Effect on Eisenia fetida and Escherichia coli

Biosynthesis belongs to one of the new possibilities of nanoparticles preparation, whereas its main advantage is biocompatibility. In addition, the ability of obtaining the raw material for such synthesis from the soil environment is beneficial and could be useful for remediation. However, the knowledge of mechanisms that are necessary for the biosynthesis or effect on the bio-synthesizing organisms is still insufficient. In this study, we attempted to evaluate the effect of quantum dots (QDs) not only on a model organism of collembolans, but also on another soil organism—earthworm Eisenia fetida—and in also one widespread microorganism such as Escherichia coli. Primarily, we determined 28EC₅₀ as 72.4 μmol L⁻¹ for CdTe QDs in collembolans. Further, we studied the effect of QDs biosynthesis in E. fetida and E. coli. Using determination of QDs, low-molecular thiols and antioxidant activities, we found differences between both organisms and also between ways how they behave in the presence of Cd and/or Cd and Te. The biosynthesis in earthworms can be considered as its own protective mechanism; however, in E. coli, it is probably a by-product of protective mechanisms.

     

Unsymmetrical Benzotristhiazole: A New Electron‐Withdrawing Core for Octupolar Chromophores

A six‐step synthesis of the unsymmetrical trimethylbenzotristhiazole has been developed. Starting from 2‐methylbenzothiazole following nitration, reduction, acetylation, thionation, and twofold cyclization, the desired trimethylbenzotristhiazole was obtained in good yield. Its condensation with donor‐substituted benzaldehydes presents the way to new octupolar chromophores. The attempt to synthesize such benzotristhiazole from dinitroaniline failed; this procedure afforded a new benzimidazole derivative.