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Organic petrography and geochemistry of the Lower-Carboniferous coals from the Ekibastuz Basin, Kazakhstan
No full textThe Bogatyr Komin open-pit mine in the Ekibastuz Basin, located in north-east Kazakhstan, is one of the largest
coal mines in the world. It is based on three Lower Carboniferous seams (from bottom to top: seams 3, 2, and 1),
which together form a 150 m thick, uniform seam complex. At the study site on the western basin edge, the seams
dip steeply. Organic petrological and geochemical investigations have been performed to determine the maturity
and depositional environment of these exceptionally thick seams.
Vitrinite reflectance (0.8–1.1 %Rr) classifies the coal as high-volatile bituminous A coal, which is also supported by Tmax values and maturity-related biomarker ratios. Vitrinite reflectance patterns prove predeformational coalification and a relatively high paleo-heat flow, likely caused by magmatic activity.
High ash yields and relatively low sulfur contents indicate that the coal accumulated in low-lying mires
without marine influence. The input of detrital minerals decreased during peat accumulation. Relatively high
concentrations of sulfur-bearing aromatic compounds, particularly in the lower part of seam 3, may reflect
volcanic activity, which is also evidenced by the presence of distinct ash layers (“kaolinitic beds”) and kaolinite
in coal samples.
Thick wood-forming plants were rare in the peat-forming vegetation. However, samples from seams 1 and 3
contain higher concentrations of aromatic compounds derived from lignin-bearing arborescent cordiaite-coniferpteridosperm vegetation. Enhanced bacterial activity during deposition of the upper part of seam 2 and seam 1 is
indicated by elevated hopane concentrations.
The exceptional thickness of the coal complex indicates a geodynamic setting with high subsidence rates
NiM/β zeolites (M = Co, Cu, and Zn) as bifunctional oxygen electrocatalysts
No full textA series of Ni/β and NiM/ β zeolites (where M =Co, Cu, and Zn) were synthesized by a low-cost aqueous ion exchange procedure from hydrogen form β zeolite (SiO2/Al2O3 = 38). After calcination and morphological examination, the materials were examined for oxygen evolution (OER) and reduction reaction (ORR) in alkaline media. Namely, all zeolites exhibited good OER and ORR activity. For OER, NiZn/β exhibited the lowest onset potential (Eonset) of 1.63 V, followed by NiCo/β (1.66 V). Overpotentials at onset (ηonset) decreased in the order: Ni/β (630 mV) > NiCu/β (610 mV) > NiCo/β (460 mV) > NiZn/β (430 mV). NiCo/β gave the highest OER current density (34.2 mA cm−2), followed by NiZn/β (19.4 mA cm−2), while NiCu/β (3.0 mA cm−2) and Ni/β zeolites (2.1 mA cm−2) gave significantly lower values. These results confirmed that NiCo/β and NiZn/β showed the highest activity for OER. For ORR, NiZn/β and Ni/β displayed the lowest Tafel slopes, indicating favorable kinetics. The half-wave potentials (E1/2) of 0.69, 0.68, 0.66, and 0.65 V were observed for Ni/β, NiZn/β, NiCu/β, and NiCo/β, respectively. NiZn/β demonstrated excellent stability and gave a number of exchanged electrons from 3.0 to 3.3, which shows mixed direct and indirect pathways of ORR, while the rest of the NiM/β zeolites predominantly showed indirect pathways of ORR. These results confirmed that NiCo/β exhibits the best activity for OER, while NiZn/β demonstrated similar OER activity to NiCo/β but showed the highest ORR activity
Anti-wrinkle potential of Serbian plant flowers
No full textPlants represent an unparalleled natural source of bioactive compounds. While the majority of scientific research focuses on roots, leaves, aerial parts, or seeds, floral organs—particularly petals—remain relatively underexplored. However, petal extracts (PEs) have often demonstrated higher bioactive content compared to other plant parts [1]. Given the long-standing tradition of cultivating ornamental plants in Serbia, locally grown floral petals offer a promising and underutilized resource for the discovery of natural anti-aging agents. One of the key targets in skin aging is the enzyme collagenase, which progressively accumulates and degrades collagen—an essential protein for skin elasticity, hydration, and structural integrity—ultimately contributing to wrinkle formation [2]. Therefore, the identification of potent natural collagenase inhibitors represents a logical and effective strategy in the search for anti-wrinkle (anti-aging) compounds.Apstrakt: [https://cherry.chem.bg.ac.rs/handle/123456789/7512
Izolovanje i karakterizacija imunoglobulina G iz zečijeg seruma
No full textImunoglobulin G je glikoprotein molekulske mase od 150 kDa i predstavlja najzastupljeniju
klasu antitela u krvi sisara i ima važnu funkciju u imunom odgovoru. Dosadašnja istraživanja su
se intenzivno bavila optimizacijom metoda za izolovanje IgG, uključujući hromatografske
tehnike poput hromatografije sa proteinom A i G, jonoizmenjivačke hromatografije i
multimodalne hromatografije. Prema dosadašnjim studijama, razvoj brzih i visoko specifičnih
metoda prečišćavanja omogućava efikasnije dobijanje IgG –a za dijagnostičke i terapijske
primene. Ipak, izazovi i dalje postoje u pogledu očuvanja stabilnosti i funkcionalnosti molekula
tokom procesa izolovanja.
Cilj ovog rada bio je prečišćavanje antigen-specifičnog imunoglobulina G (IgG) iz seruma
zečeva imunizovanih proteinom kikirikija, Ara h 2, jednim od glavnih alergena kikirikija. IgG je
prečišćena primenom afinitetne hromatografije zasnovane na interakciji sa proteinom G, koji
specifično vezuje Fc fragment imunoglobulina G. Prečišćeni IgG je analiziran elektroforetski
(SDS-PAGE) radi provere čistoće i prisustva teških i lakih lanaca IgG-a, nakon čega je
proverena i njihova specifičnost u imunološkim testovima poput Western blot-a i ELISA testa.
Na osnovu dobijenih rezultata utvrđeno je da afinitetna hromatografija sa proteinom G pokazuje
visoku efikasnost prilikom izolovanja antitela iz seruma zečeva. Provera specifičnosti, ELISAom
i Western blot-om, ukazuje da izolovani IgG specifično prepoznaje alergen kikirikija Ara h
2
Fitohemijski profil i biološka aktivnost ekstrakata mikrobilja i klica
No full textZbog sve češće primene mikrobilja i klica u prehrambenoj industriji, hemičari širom sveta su počeli da analiziraju ove biljne vrste, kako bi proširili i unapredili njihovu primenu i u drugim granama industrije. Najvažnija jedinjenja koja ulaze u sastav mikrobilja i klica su antioksidansi, u koje se ubrajaju fenolna jedinjenja, terpeni i saponini. U okviru ovog rada ispitani su fitohemijski profil i biološka aktivnost devet uzoraka klica i jedanaest uzoraka mikrobilja. Određivanje fitohemijskog profila podrazumevalo je optimizaciju mobilne faze za razvijanje fenolnog profila, derivatizaciju u odgovarajućim jedinjenjima i spektrofotometrijsko određivanje ukupnog sadržaja fenola. Biološka aktivnost podrazumevala je spektrofotometrijsko određivanje antioksidativne aktivnosti i bioautografiju, koja uključuje određivanje antibakterijske aktivnosti na Gram-pozitivne i Gram-negativne bakterije i određivanje antidijabetske aktivnosti spektrofotometrijskim amilaza testom. Kao rastvarač za ekstrakciju odabran je metanol zbog svoje polarne prirode i dobre rastvorljivosti bioaktivnih komponenti. U radu je potvrđeno da su ekstrakti mikrobilja i klica bogati biološki aktivnim jedinjenjima, kao i da svaka vrsta pokazuje karakterističan hemijski profil. Dodatno, mikrobilje i klice se međusobno razlikuju po sadržaju metabolita različitih od fenolih jedinjenja. Ovi podaci se mogu primeniti u prehrambenoj industriji, radi izrade suplemenata i dodataka ishrani, farmaceutskoj i kozmetičkoj industriji, radi proizvodnje krema, seruma i preparata protiv starenja kože, i poljoprivrednoj industriji, radi optimizacije uslova uzgoja mikrobilja i klica
Cation recognition by benzene sandwich compounds – a DFT perspective
No full textCation–π interactions between alkali, alkaline earth and ammonium cations and sandwich compounds of benzene and the cyclopentadienyl (Cp) anion were studied using quantum chemical CCSD(T)/CBS and DFT (B3LYP/def2-TZVP) calculations. The results show significantly stronger interactions of sandwich compounds with respect to (uncoordinated) benzene. Moreover, very strong cation–π interactions of Cp sandwich compounds are furthermore surpassed by cation–π interactions of benzene sandwich compounds, which are capable of reaching a remarkable interaction energy value of −196.8 kcal mol−1 (Mg2+/W(benzene)2). While there are only small variations of interaction energy values for sandwich compounds of different transition metals (3d metals < 4d < 5d), cation–π interactions progressively become stronger in the following order: (uncoordinated) benzene < Cp sandwich < benzene sandwich. Aside from interaction energies, the cation–π interactions can be assessed by means of their influence on the geometries of sandwich compounds, which are found to strongly correlate with the strength of cation–π interactions. These results emphasize sandwich compounds, particularly those containing C6 aromatic rings, as promising candidates for new receptors for common metal cations
Sinteza i karakterizacija La-MOF nanočestica i njihova primena u modifikaciji štampane ugljenične elektrode za elektohemijsko određivanje Bisfenola A
No full textU savremenim naučnim istraživanjima veliki značaj se pridaje razvoju naprednih funkcionalnih materijala koji omogućavaju efikasno otkrivanje i kvantifikaciju štetnih supstanci u životnoj sredini i svakodnevnoj upotrebi. BPA je industrijska hemikalija široke primene, poznata po potencijalno štetnim efektima na ljudsko zdravlje, naročito kao endokrini disruptor. Zbog toga je razvoj senzora za njegovo selektivno i osetljivo detektovanje od izuzetne važnosti.
U ovom radu istražuje se sinteza i karakterizacija nanočestica MOF baziranog na lantanu (La-MOF), kao i njihova primena u modifikaciji ekonomski pristupačne SPCE. Primarni cilj rada je razvoj elektrohemijskog senzora zasnovanog na La-MOF/SPCE modifikaciji, sa poboljšanim analitičkim performansama za detekciju BPA.
Sinteza La-MOF nanočestica je izvršena hidrotermalnom metodom, dok je karakterizacija obavljena XRD i SEM, koje su potvrdile strukturu i morfologiju dobijenog materijala. Elektrohemijska svojstva modifikovane elektrode ispitana su tehnikama CV i DPV, kako bi se procenila njena efikasnost u prisustvu BPA.
Rezultati pokazuju da modifikacija SPCE elektrode pomoću La-MOF nanočestica značajno poboljšava elektrohemijsku osetljivost i selektivnost senzora, što ovu platformu čini pogodnom za primenu u detekciji tragova BPA u realnim uzorcima
Binding of the commonly used antioxidants (quercetin, resveratrol, and dihydrolipoic acid) to major circulating proteins – spectroscopic and in silico docking and molecular dynamic simulation studies
No full textPoor bioavailability and reduced stability are the main drawbacks to efficiently utilizing many naturally occurring antioxidants, so their binding to circulatory proteins is essential. This work investigated whether major human circulatory proteins, besides albumin, including transferrin, alpha-2-macroglobulin, and fibrinogen, bind widely consumed antioxidants and food supplements, including quercetin, trans-resveratrol, and dihydrolipoic acid, thus filling the gap of detailed pharmacokinetic properties of these food supplements. Detailed examination of the protein structural and functional changes that occur upon ligand binding was analyzed by spectroscopic methods and in silico docking and molecular dynamic simulation studies on the model that consists of the protein/antioxidant pair with the highest affinity constant. It was found that alpha-2-macroglobulin binds trans-resveratrol with the highest affinity (Ka of 4.5 x 104 M−1). In silico results revealed four potential binding sites between trans-resveratrol and alpha-2-macroglobulin, with hydrogen bonds being crucial for binding, while other observed interactions (primarily aromatic interactions) are of secondary importance. The binding of trans-resveratrol to alpha-2-macroglobulin leads to mutual protection of both molecules from oxidative stress and significantly increased hidrosolubility of resveratrol, both of which could serve to increase the bioavailability and bioactivity of resveratrol in circulation
Proučavanje kinetike Lipaze A iz bakterije Bacillus subtilis i njenog mutanta u različitim rastvaračima primenom molekulsko-dinamičkih simulacija
No full textPredstavljena studija ispituje strukturne i kinetičke osobine lipaze A divljeg tipa (WT) i mutanta (MT20) iz bakterije Bacillus subtilis, sa fokusom na stabilnost u vodenim rastvorima i u prisustvu 60% metanola. Eksperimentalni podaci pokazuju da mutant MT20 ima značajno poboljšanu stabilnost i zadržava enzimska svojstva pri visokim koncentracijama metanola, dok WT enzim gubi aktivnost. Simulacije molekulske dinamike potvrdile su date pronalaske, otkrivajući smanjenu fleksibilnost i promene u konformaciji kod MT20 u poređenju sa WT, posebno u blizini aktivnog mesta. RMSD, RMSF, i analiza radijusa žiracije, sa reljefima slobodne energije, potvrdila je superiornu stabilnost mutanta u okruženju organskih rastvarača. Rezultati ističu potencijal primene takvih lipaza u industriji proizvodnje biodizela
Određivanje toksičnih i esencijalnih elemenata u uzorcima kortikalnog dela butne kosti
No full textCiljevi ovog završnog rada su:
1. Utvrditi sadržaj esencijalnih i toksičnih metala u korikalnom delu butne kosti kod stanovništva koje živi na teritoriji grada Kragujevca;
2. Analizirati rezultate istraživanja u Republici Srbiji i uporediti dobijene rezultate sa rezultatima istraživanja koje se odnose na stanovništvo iz drugih delova sveta