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Квантнохемијско проучавање C–H···O интеракција између HTcO₄ и ароматичних аминокиселина
No full textThis study investigates C–H···O interactions between HTcO₄ and aromatic amino acids (phenylalanine, tyrosine, and tryptophan) through quantum-chemical calculations. The interaction energies calculations were combined with the analysis of Molecular Electrostatic Potentials (MEP) to understand the nature of these interactions. The strongest interaction was observed for the HTcO₄–tryptophan with an energy minimum of -9.53 kJ/mol at a distance of 2.1 Å. Phenylalanine showed a similarly strong interaction, with a minimum of -9.49 kJ/mol, while tyrosine exhibited the weakest interaction, with a minimum of -8.61 kJ/mol. Electrostatic potential maps confirmed the electrostatic nature of the C–H···O interactions, highlighting the role of the oxygen atoms in acting as hydrogen bond acceptors. These findings suggest that the position of the hydrogen atoms relative to the substituents on the aromatic ring influences the strength of the interactions. The results presented here could be of great importance for the recognition of new, overlooked noncovalent contacts between pertechnetic acid and amino acid fragments and a better understanding of the stability of pertechnetate-peptide complexes.У овом раду су проучаване C–H···O интеракције између HTcO₄ и ароматичних аминокиселина (фенилаланин, тирозин и триптофан) коришћењем квантнохемијских прорачуна. Резултати прорачуна енергије интеракција су комбиновани са анализом молекулских електростатичких потенцијала (MEП) ради бољег разумевања природе ових интеракција. Најјача интеракција је израчуната у систему HTcO₄–триптофан са минимумом од -9,53 kJ/mol на растојању од 2,1 Å. Фенилаланин је показао сличну јачину интеракције (9,49 kJ/mol), док тирозин има најслабију интеракцију (-8,61 kJ/mol). Анализа мапе електростатичког потенцијал је потврдила електростатичку природу C–H···O интеракција, наглашавајући улогу атома кисеоника као акцептора водоника у водоничним везама. Ови резултати пружају значајан увид у улогу C–H···O интеракција у молекулском препознавању и дизајну функционалних материјала са пертехнетатским јединицама. Добијени резултати указују да положај атома водоника у односу на супституенте на ароматичном прстену утичу на енергију ових интеракција. Ови резултати могу бити од великог значаја за препознавање нових нековалентних контаката између пертехницијумове киселине и фрагмената амино киселина, као и за боље разумевање стaбилности комплекса пертехнетата и пептида.Accepted version: [https://cer.ihtm.bg.ac.rs/handle/123456789/8278
Rare earth elements and health risk assessment of road dust from the vicinity of coal fired thermal power plants
No full textAs emerging pollutants, rare earth elements (REEs) have been explored in different environmental samples. This is the first study to use road dust samples to monitor REEs form the vicinity of thermal power plant (TPPs). Road dust samples were collected from 17 locations (main and side roads) in a 15 km radius surrounding two coal-fired TPP (TPP Kostolac A & B, Serbia). Concentrations of nine REEs (Sc, La, Ce, Nd, Sm, Eu, Tb, Dy, Yb) were measured in the road dust samples (f < 63 μm, easily resuspended fraction size) using instrumental neutron activation analysis (INAA). We have found that the concentrations of REEs do not depend on the distance of the sampling location from TPP. There were no statistically significant differences between the main road and side road samples suggest that traffic is not the main source of REE in the studied area. Principal component analysis, hierarchical cluster analysis as well as geo-accumulation index (Igeo) and enrichment factors (EF) point to an enrichment with Dy of road dust samples collected in September. The road dust samples do not pose any harm to human health in the tested area, as shown by a hazard index of less than 0.1. Despite the low REE risk, it is important to consider the possibility of negative health consequences, mainly because these samples may contain numerous other organic and inorganic pollutant
Evaluation of Surface Properties in Biosilica-Reinforced Biobased Polyester Nanocomposites
No full textThis study investigates the surface properties of bio-based unsaturated polyester resin (b-UPR) nanocomposites reinforced with biosilica nanoparticles derived from rice husk. The b-UPR matrix was synthesized from recycled polyethylene terephthalate (PET) and renewable monomers, providing a sustainable alternative to conventional polyester resins. Unmodified and modified biosilica particles with silanes: (3-trimethoxysilylpropyl methacrylate—MEMO, trimethoxyvinylsilane—VYNIL, and 3-aminopropyltrimethoxysilane with biodiesel—AMBD) were incorporated in different amounts to evaluate their influence on the wettability, topography, and viscoelastic behavior of the composites. Contact angle measurements revealed that the addition of modified biosilica significantly improved the hydrophobicity of the b-UPR surface. The greatest increase in the wetting angle, amounting to 79.9% compared to composites with unmodified silica, was observed in the composites containing 5 wt.% SiO2-AMBD. Atomic force microscopy (AFM) analysis indicated enhanced surface roughness and uniform dispersion of the nanoparticles. For the composite containing 1 wt.% of silica particles, the surface roughness increased by 25.5% with the AMBD modification and by 84.2% with the MEMO modification, compared to the unmodified system. Creep testing demonstrated that the reinforced nanocomposites exhibited improved dimensional stability under sustained load compared to the neat resin. These findings confirm that the integration of surface-modified biosilica not only enhances the mechanical properties but also optimizes the surface characteristics of bio-based polyester composites, broadening their potential for high-performance and sustainable applications
Detection and Quantification of Adulterants in Beeswax using 1H NMR Spectroscopy
No full textHericium erinaceus is considered one of the most promising medicinal fungi for the treatment
of neurodegenerative diseases, containing a wide variety of bioactive compounds, including
hericenones, erinacines, and many other related molecules, which exhibit significant
neurotrophic and neuroprotective properties. Previous studies demonstrated that erinacine-
enriched mycelium of H. erinaceus can delay neuronal cell death in animal models of
neurodegenerative conditions such as Alzheimer’s disease and ischemic stroke. [1] Our
research focus on the isolation of a diverse range of bioactive compounds from employing
conventional chromatographic techniques, followed by their structural characterization
predominantly through nuclear magnetic resonance (NMR) spectroscopy. Hericene A was
isolated from the ethyl acetate extract of the H. erinaceus fruiting bodies by performing
gravitational chromatography, followed by additional purification on semi-dry flash
chromatography. Furthermore, erinacines A and C were isolated from the ethyl acetate extract
of the mycelium. The extract was initially processed through semi-dry flash chromatography
followed by subsequent purification utilizing preparative high-performance liquid
chromatography (HPLC). The structures of isolated compounds were determined using 1D (¹H
NMR and 13C) and 2D (COSY, J RES, HMBC, HSQC, and NOESY) NMR experiments. These
purification methodologies demonstrated high efficiency and cost-effectiveness, resulting in
the isolation of pure natural compounds appropriate for subsequent pharmacological
investigations. Future investigations will prioritize the optimization of isolation protocols for
various metabolites derived from both the mycelium and fruiting bodies of H. erinaceus,
alongside comprehensive characterization and systematic evaluation of their biological
activities, with the aim of elucidating potential therapeutic applications in the treatment of
neurodegenerative disorders, particularly Alzheimers disease
In silico evaluation of drug-likeness properties of steroidal semicarbazones and steroidal oxazolo[4.5-b]quinoxalines
No full textAntibiotic resistance is accelerating at an alarming rate, emerging as a major global
threat with the potential to undermine nearly a century of therapeutic progress. Consequently,
the scientific community is investing considerable effort into the discovery of novel antimicrobial
agents. In this study, the in silico drug-likeness of steroidal semicarbazones (SCs) with varying C-
17 substituents and their corresponding oxazolo[4.5-b]quinoxalines (Qxs) was assessed using
publicly available online platforms ‒ Molinspiration, preADMET, and pkCSM. According to
Lipinski’s Rule of Five (Ro5), all compounds, except the cholestane-based Qx, meet the drug-
likeness criteria. Functionalization of SCs into Qxs resulted in a marked increase in lipophilicity
(by more than two units) and further reduced already low water solubility, thereby causing Qxs
to violate Ro5. Nevertheless, the Qxs demonstrated excellent predicted pharmacokinetic
properties, including maximal predicted intestinal absorption (IA=100%), favorable steady-state
volume of distribution (VDss > 0.44, log L/kg), and limited blood–brain barrier (BBB)
permeability. Notably, the androstene- and progesterone-based Qxs exhibited reduced BBB
permeability compared to their parent SCs, suggesting a potentially lower risk of neurotoxicity.
The obtained results indicate that drug-like steroidal Qxs may serve as promising candidates for
synthesis and further evaluation of antimicrobial activity
The Comprehensive Study of TiO2 Blocking Layer with Complementary Electrochemical and SPM Methods for the Application in Photovoltaics
No full textThe blocking layer is crucial for inhibiting recombination processes in photovoltaics that utilize oxide semiconductors, such as dye-sensitized solar cells (DSSCs), quantum-dot-sensitized solar cells (QDSSCs), and perovskite solar cells. However, its effectiveness strongly depends on the chosen deposition method. This study systematically evaluates the most suitable approach for obtaining a uniform, pinhole-free titanium dioxide (TiO2) blocking layer by using three deposition methods: radio-frequency sputtering, spin-coating, and chemical bath deposition. The electrochemical, optical, and morphological properties of blocking layers were characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), UV-VIS spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and Kelvin probe force microscopy (KPFM). KPFM analysis, together with CV and EIS, revealed that the lower Rct values and higher CV currents observed in spin-coated (SC_11-33) and vertically deposited CBD films (CB_5, CB_6) resulted from incomplete FTO coverage. In contrast, sputtered (SP_21-24) and horizontally deposited CBD films (CB_1, CB_2) demonstrated significantly higher Rct values and improved surface coverage. Full DSSCs fabricated with SP_23, SC_33, and CB_2 confirmed the correlation between interfacial properties and photovoltaic performance. This combined approach offers a fast, material-efficient, and environmentally conscious screening method for optimizing blocking layers in solar cell technologies
Biomarker fingerprint as a forensic tool for oil spill source identification in alluvial sediments
No full textOil pollutants are among the widespread contaminants in the world. Their content and composition is influenced by both, the content of the original crude oil or its derivative, and by the environmental
conditions at the location of their spillage. Although the environmental conditions can change significantly the content of oil pollutants, their biomarker fingerprint can remain intact and therefore can be used for the source identification.
The aim of this study was application of saturated biomarkers for oil spill source identification in alluvial sediments. The investigated location is located in the alluvial plain of the Sava River, in the vicinity of the heating plant in New Belgrade, Serbia, and it is covering the surface area of 300 000 m2.
Surface soil and sediment samples were collected at several microlocations from this locality. From
these samples extractable organic matter was isolated with dichloromethane using a Soxhlet apparatus. Saturated hydrocarbons were isolated from the extracts using a column chromatography and analyzed by GC-MS. The instrumental analysis included typical petroleum biomarkers: n-alkanes in the (m/z = 71), steranes (m/z = 217) and terpanes (m/z = 191). The analytical procedure employed was described in our previous papers.[1,2]
The distribution of the n-alkanes revealed that most of the samples contained a mixture of an oil
pollutant and a native organic matter. Their ratio varied depending on the distance from the heating plant, which was the only suspected source of oil pollution in this area. The analyses of steranes and terpanes showed that, at some locations, different oil pollutants were present. These results suggested that multiple discharges of the oil pollutants to the surrounding soil occurred over the years.
According to these results it can be concluded that biomarker fingerprint can be a useful tool for oil spill identification and source discrimination in alluvial sediments
Interdisciplinary projects for developing environmental literacy and environmental identity of primary school students
No full textEnvironmental literacy and environmental identity are the key concepts of Education for Sustainable Development. Environmental literacy refers to the understanding of basic principles of how the environment functions, critical thinking related to environmental issues and responsible decision-making based on the acquired knowledge and pro-environmental behavior. Environmental identity, on the other hand, refers to the relationship of an individual with the nature and the sense of responsibility for preserving it.One of the quality standards of educational institutions in the Republic of Serbia is their active involvement in promotion of sustainable development. This is achieved through the education of students on ecological topics and development of their responsible attitude towards the natural environment. Within this context, the school and the teacher play a crucial role in designing and implementing activities that stimulate environmental literacy and develop students’ environmental identity. This can be achieved by project-based learning and activities that interrelate theoretical knowledge and its application in real life. Project-based activities involve the examination of real problems, planning and applying solutions to the identified problems, student collaboration and the application of interdisciplinary approach that enables integration of the acquired knowledge into practical results.The aim of this paper is to present the scenario of a project-based activity entitled Practical measures for sustainable development in school in which students combine the contents of biology, chemistry and geography. The outputs of such a project activity enable not only the development of knowledge and skills in various disciplines but also strengthen the students’ sense of belonging to the community and their responsibility towards the natural environment. This paper emphasizes the significance of project-based learning as an efficient educational model that encourages young generations to contribute to sustainable development and build their environmental identity
From waste to fertile soil: bioremediation and humic acid synthesis as an indicator of revitalization
No full textSoil is a key component of terrestrial ecosystems, and its fertility
strongly depends on the quantity and quality of organic matter. Humic acids
represent one of the most stable fractions of soil organic matter and serve
as an important indicator of soil fertility and long-term ecological
sustainability. In recent years, the valorization of waste materials through
bioremediation has attracted growing attention as a strategy to address
both environmental pollution and soil degradation. Bioremediation
processes not only enable the detoxification and mineralization of organic
pollutants, but also contribute to the transformation of waste-derived
substrates into humic substances.
This study discusses the potential of bioremediation in converting
industrial and organic waste streams from the petrochemical industry into
value-added products, focusing on the generation of humic acids. The
formation and accumulation of humic acids during biodegradation reflect
the stabilization of organic matter, improved soil quality, and serve as
measurable markers of soil revitalization. Moreover, the ratio of humic to
fulvic acids provides insights into soil organic matter composition, with a
lower ratio indicating reduced aromaticity and greater similarity to fulvic
acids. These parameters also serve as indicators of soil fertility, as higher
levels of humification are associated with enhanced nutrient retention,
increased cation exchange capacity, improved water-holding properties,
and overall biological functionality of soils. To determine the optical density
of a sample containing humic and fulvic acids, the E4/E6 ratio (absorbance
ratio at 465 and 665 nm) is used (Table 1). This ratio increases as the
average molecular weight of the sample decreases, which means that a
higher E4/E6 value indicates a greater presence of fulvic acids relative to
humic acids
A green approach for obtaining functional food ingredients from medlar (Mespilus germanica) by fungal cellulase enzymes
No full textFungal cellulase enzymes were applied to medlar fruit to obtain and characterize insoluble dietary fibers (IDF) for the first time. Medlar, an underutilized fruit, was treated with cellulase enzymes produced by non-toxigenic Aspergillus welwitschiae and Aspergillus tubingensis. The enzymatic treatment enhanced the water retention capacity (WRC) by 15%, oil retention capacity (ORC) by 5%, and swelling capacity in water and oil by 48% and 12%, respectively, compared to untreated samples. Microscopic analysis confirmed partial hydrolysis of lignocellulosic components, leading to improved porosity and functional properties. These results demonstrate the potential of medlar-derived IDF as a valuable ingredient for fiber-enriched and functional foods. The study also highlights the sustainable use of fungal cellulase enzymes as a safe and eco-friendly approach with promising applications in the food, feed, and biotechnology industries