Application of oxidation processes in the purification of wastewaters from phenolic compounds

Natural phenolic compounds are significant component of the human diet, as they are present in fruits and vegetables, and they have very important biological activity in the living organisms. Because of their structure, they are subject of numerous oxidation processes, such as autoxidation, but are easily to oxidize in presence of various oxidizing agents and enzymes. Many authors have been investigating phenolic oxidation processes, and have successfully identified their pathways and a significant number of intermediates and products generated by these processes. Also, particular attention has been made to the effects of these processes on food quality and other biological processes in living organisms. Phenols are persistent pollutants of water systems from various agricultural activities and industrial wastewater discharges. It is known that the presence of phenolic compounds in water supplies and industrial effluents directly affects natural processes in the environment due to their toxicity and natural ability to decompose. This property, to easily oxidize and, as a result of it, to mineralize, is practically useful for the treatment of the wastewaters, so it is of global concern to manage the best technology to remove phenols and other organic pollutants, assisted with the oxidation processes. In the aspect of treatment of wastewaters polluted with phenols, we reviewed oxidative processes such as autoxidation, enzyme-catalyzed oxidation, photo-oxidation, electrochemical oxidation and oxidation by Fenton's reagent and, based on the literature data, we presented advantages and disadvantages of these processes compared to each other. © 2020 Editura Academiei Romane. All rights reserved

Supplementary data for article: Minic, S. L.; Milcic, M.; Stanic-Vucinic, D.; Radibratovic, M.; Sotiroudis, T. G.; Nikolic, M. R.; Velickovic, T. C. Phycocyanobilin, a Bioactive Tetrapyrrolic Compound of Blue-Green Alga Spirulina, Binds with High Affinity and Competes with Bilirubin for Binding on Human Serum Albumin. RSC Advances 2015, 5 (76), 61787–61798. https://doi.org/10.1039/c5ra05534b

Supplementary material for: [https://doi.org/10.1039/c5ra05534b]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1741

Supplementary data for article: Minic, S. L.; Milcic, M.; Stanic-Vucinic, D.; Radibratovic, M.; Sotiroudis, T. G.; Nikolic, M. R.; Velickovic, T. C. Phycocyanobilin, a Bioactive Tetrapyrrolic Compound of Blue-Green Alga Spirulina, Binds with High Affinity and Competes with Bilirubin for Binding on Human Serum Albumin. RSC Advances 2015, 5 (76), 61787–61798. https://doi.org/10.1039/c5ra05534b

Supplementary material for: [https://doi.org/10.1039/c5ra05534b]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/1741

Spatiotemporal variability of air temperatures in Central Serbia from 1949 to 2018

The paper presents trends for three categories of variables: average annual, average maximum and average minimum air temperatures. Data was provided by the meteorological yearbooks of the Republic Hydrometeorological Service of Serbia. The main goal of this paper is to detect possible temperature trends in Central Serbia. The trend equation, trend magnitude, and Mann-Kendall non-parametric test were used in the analysis of climate parameters. The used statistical methods were supplemented by GIS numerical analysis, which aimed to analyze the spatial distribution of isotherms from 1949 to 2018. The obtained results indicate that out of the 72 analyzed time series, an increase in air temperature is dominant in 61 time series, while 11 time series show no changes. The highest increase was recorded in the average maximum time series (4.2 °C), followed by an increase of 3.5°C in average maximum air temperatures. The highest increase in the average annual time-series was 3.0 °C. The lowest increases in air temperature were recorded in the average minimum time series (0.1 and 0.2 °C). In two average minimum time series a decrease in average air temperatures was identified (-0.6 and -0.4 °C. The application of GIS tools indicates the existence of interregional differences in the arrangement of isotherms, leaded by the orography of the terrain. In the spatial distribution of the analyzed variables, "poles of heat" and "poles of cold" stand out, and the influence of the urban heat island is evident (especially in the case of the urban agglomeration of Belgrade). The manifested spatial patterns of air temperature need to be further examined and the correlation with possible causes need to be determined. For these reasons, the paper provides a solid basis for studying the climate of this area in the future, as it provides insight into climate dynamics over the past decades

Structural and electronic properties of screen-printed Fe2O3/TiO2 thick films and their photoelectrochemical behavior

Nanostructured Fe2TiO5 thick films were deposited on fluorine-doped tin oxide glass substrate using screen printing technology. Starting hematite and anatase nanopowders were mixed in molar ratios 1:1 and 1:1.5 and calcined in air at 900°C for 2 h to form pseudobrookite, Fe2TiO5. Functional powders and sintered thick films were analyzed by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and transmission electron microscopy. UV–Vis analysis enabled determination of the band gap. Separation and transfer efficiency of photogenerated charge carriers was confirmed by the photoluminescence and electrochemical impedance spectra. Even though a slightly high onset oxygen evolution potential of photoexcited film electrode samples in NaOH was obtained, photocurrent densities were high, especially in the presence of H2O2 (~12 mA cm−2 at 1.7 V RHE). This work shows promise for practical application due to favorable band positions of pseudobrookite and low-cost screen printing technology

СУПЕРКАПАЦИТИВНА СВОЈСТВА УГЉЕНИЧНИХ МАТЕРИЈАЛА ДОБИЈЕНИХ ИЗ СAХАРОЗЕ И АКТИВИРАНИХ ХИДРОКСИДИМА АЛКАЛНИХ МЕТАЛА

The influence of different hydroxides, applied to activate carbon black, on the electrochemical properties of activated carbon was investigated. The carbon material was prepared by hydrothermal treatment of sucrose and afterwards thermally activated using KOH, NaOH and LiOH. The electrochemical properties of the obtained samples were examined by cyclic voltammetry and electrochemical impedance spectroscopy and correlated to their physicochemical properties. All samples showed characteristic capacitor-like behaviour. The highest specific capacitance was obtained for the KOH-treated sample, while the increase in capacitance follows the sequence of the growth of ionic radius of a metal from an alkali which is used for activation. It was found that the dependence on the type of hydroxide is due to differences in the radii of a metal. The alkalies of larger radii of metal generated make pores wider and consequently the structure of a porous layer become more accessible to the charge transfer of capacitive response

Nutraceutical phycocyanobilin binding to catalase protects the pigment from oxidation without affecting catalytic activity

Phycocyanobilin is a dark blue linear tetrapyrrole chromophore covalently attached to protein subunits of phycobiliproteins present in the light-harvesting complexes of the cyanobacteria Arthrospira platensis (Spirulina “superfood”). It shows exceptional health-promoting properties and emerging use in various fields of bioscience and industry. This study aims to examine the mutual impact of phycocyanobilin interactions with catalase, a life-essential antioxidant enzyme. Fluorescence quenching experiments demonstrated moderate binding (Ka of 3.9 × 104 M−1 at 25 °C; n = 0.89) (static type), while van't Hoff plot points to an enthalpically driven ligand binding (ΔG = −28.2 kJ mol−1; ΔH = −41.9 kJ mol−1). No significant changes in protein secondary structures (α-helix content ~22%) and thermal protein stability in terms of enzyme tetramer subunits (Tm ~ 64 °C) were detected upon ligand binding. Alterations in the tertiary catalase structure were found without adverse effects on enzyme activity (~2 × 106 IU/mL). The docking study results indicated that the ligand most likely binds to amino acid residues (Asn141, Arg 362, Tyr369 and Asn384) near the cavity between the enzyme homotetramer subunits not related to the active site. Finally, complex formation protects the pigment from free-radical induced oxidation (bleaching), suggesting possible prolongation of its half-life and bioactivity in vivo if bound to catalase

Synthesis, characterization and SAR studies of bis(imino)pyridines as antioxidants, acetylcholinesterase inhibitors and antimicrobial agents

In this study we synthesized a series of sixteen bis(imino)pyridines (BIPs) starting from 2,6-diaminopyridine and various aromatic aldehydes, and evaluated their antioxidant, antibacterial, antifungal and acetylcholinesterase (AChE) inhibitory activity. The chemical structures were elucidated by FTIR, elemental analysis, ESR and HRMS. H-1 and C-13 NMR spectra couldn't be acquired due to the formation of stable, carbon-centered radical cations in a solution, as confirmed by ESR spectroscopy and DFT calculations. The in vitro antioxidant potency was evaluated using four assays: free radical scavenging activity (DPPH and ABTS), reducing power and total antioxidant capacity assay. BIPs demonstrated excellent antioxidant properties, and two derivatives proved to be more potent than reference antioxidants (ascorbic acid and Trolox) in all assays. DFT calculations on.B97XD/6-311++g(d,p) level of theory provided valuable insights into the radical scavenging mechanism of BIPs. For hydroxyl-substituted BIPs, hydrogen atom transfer (HAT) is a predominant mechanism, while the single electron transfer coupled with proton transfer (SET-PT) governs the antioxidant activity of other derivatives. Intramolecular hydrogen bonding (IHB) plays an important role in the mechanism of antioxidant activity as revealed by noncovalent interaction analysis and rotational barrier calculations. The spin density of radical cations is localized on carbon atoms of a pyridine ring, which corroborates with g-factors and multiplicity obtained from ESR analysis. The most potent BIP exhibited moderate inhibitory activity toward AChE (IC50 = 20 +/- 4 mu M), while molecular docking suggested binding at the peripheral anionic site of AChE with the MMFF94 binding enthalpy of -43.4 kcal/mol. Moderate in vitro antimicrobial activity of BIPs have been determined against several pathogenic bacterial strains: Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecalis, Staphylococcus aureus and clinical isolate of methicillin resistant S. aureus (MRSA). The antifungal activity of BIPs toward Candida albicans was also confirmed. The similarity ensemble approach combined with molecular docking suggested leucyl aminopeptidase as the probable antimicrobial target for the three most potent BIP derivatives

Phycocyanobilin, a bioactive tetrapyrrolic compound of blue-green alga Spirulina, binds with high affinity and competes with bilirubin for binding on human serum albumin

Human serum albumin (HSA) is an important regulator of the pharmacokinetic properties of bioactive compounds. Phycocyanobilin is a blue tetrapyrrole chromophore of C-phycocyanin with proven health-promoting activities. Despite its structural similarity to bilirubin, the conformation it adopts in aqueous solution is different and the pigment is more soluble than bilirubin. The aim of our study was to examine binding of phycocyanobilin for HSA and to investigate its competition with bilirubin. Based on a computational approach, we demonstrated two putative high-affinity binding pockets on HSA of virtually identical energies for the neutral and anion forms of bilirubin, but with slightly favorable predictions for anion forms of phycocyanobilin. Computational prediction of phycocyanobilin pK(a) values suggested a monoanion form to be the most stable form at physiological conditions. The computationally predicted binding sites for phycocyanobilin were identical to the two previously identified binding sites for bilirubin (subdomains IB and IIA). Results obtained by protein and pigment fluorescence measurements, circular dichroism, and competition experiments confirmed high affinity (binding constant of 2.2 x 10(6) M-1 at 25 degrees C), stereo-selective binding of phycocyanobilin M-conformer to HSA and its competition with bilirubin, warfarin and hemin. Our experimental data confirm that phycocyanobilin binds to IB and IIA binding site of HSA with an affinity similar to bilirubin. In conditions characterized by an increased bilirubin plasma concentration, or intake of drugs binding to IB or IIA binding site, pharmacokinetics of phycocyanobilin may also be changed.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3403

Advanced thermal camera based system for object detection on rail tracks

In this paper, an advanced thermal camera-based system for detection of objects on rail tracks is presented. Developed system is powered by advanced image processing algorithm, in order to achieve greater reliability and robustness, and tested on set of infrared images captured at night conditions. The goal of this system is to detect objects on rail tracks and next to them and estimate distances between camera stand and detected objects. For that purpose, different edge detection methods are tested, and finally Canny edge detector is selected for rail track detection and for determination of region of interest, further used for analysis in object detection process. In determined region of interest, region-based segmentation is used for object detection. For estimation of distances between camera stand and detected objects, homography based method is used. Validation of estimated distances is done, in respect to real measured distances from camera stand to objects (humans) involved in experiment. Distances are estimated with a maximum error of 2%. System can provide reliable object detection, as well as distance estimation, and for improved robustness and adaptability, artificial intelligence tools can be used