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The influence of a precursor layer and ionic strength on the formation and properties of chitosan/pectin polyelectrolyte multilayer
No full textPolielektrolitni višeslojevi su tanki filmovi koji nastaju naizmjeničnom adsorpcijom suprotno nabijenih polielektrolita na čvrstu površinu. Filmovi izgrađeni od prirodnih polielektrolita, poput kitozana i pektina, posebno su zanimljivi zbog biokompatibilnosti i netoksičnosti, ali i antimikrobnih svojstava što ih čini pogodnim kandidatima za primjenu kao zaštita površine voća. U prvom dijelu ovog diplomskog rada istraživan je utjecaj ionske jakosti i ishodnog sloja na nastajanje i svojstva polielektrolitnog višesloja kitozan/pektin, dok je u drugom dijelu ispitana adhezija bakterije Staphylococcus aureus na njegovu površinu. Površinska svojstva poput debljine, hrapavosti, morfologije i močivosti pripravljenih višeslojeva određena su korištenjem elipsometrije, tenziometrije i mikroskopije atomskih sila. Nadalje, pretražnom elektronskom mikroskopijom određena je prekrivenost površine višeslojeva bakterijama nakon inkubacije. Rezultati pokazuju na to da ionska jakost te ishodni sloj utječu na svojstva višesloja kitozan/pektin, dok istraživanja adhezije bakterija ukazuju da je višesloj kojem je završni sloj kitozan učinkovitiji protiv adhezije bakterije S. aureus od višesloja koji završava pektinom.Polyelectrolyte multilayers are thin films prepared by alternating adsorption of oppositely charged polyelectrolytes to a solid surface. Such materials, when prepared out of biocompatible and non-toxic polyelectrolytes, for instance chitosan and pectin, have shown to be suitable as protective coatings on fruits due to their antimicrobial properties. The first part of this thesis focuses on the influence of ionic strength and the precursor layer on the formation and properties of the chitosan/pectin multilayer, while the second part covers bacterial adhesion of Staphylococcus aureus to the multilayer. The surface properties and thickness of the multilayer were investigated by ellipsometry, tensiometry and atomic force microscopy. In addition, surface coverage of the film with S. Aureus after adhesion experiments was determined with scanning electron microscopy. The results have shown that both ionic strength and the precursor layer influence the multilayer properties. Finally, adhesion experiments indicate that the chitosan-terminating multilayer is more efficient against adhesion than the pectin-terminating one
Detekcija benignih varijanti broja kopija analizom kromosomskih mikročipova u hrvatskoj populaciji
No full textCopy number variants are characterized by losses or gains of DNA sequences in a range from 50 base pairs (pb) up to several megabase (Mb) for each copy. The clinical significance of CNVs is classified according to the guidelines of the American College for Medical Genetics and Genomics. Benign copy number variants are widespread in the general population and have no clinical significance. As part of this research, a retrospective-prospective analysis was conducted based on results for 400 patients referred for diagnostic treatment for various types of neurodevelopmental disorders, in the period from September 2021 to May 2023. As part of the research, a register of benign CNVs of the Croatian population is established. The significantly higher frequency of benign CNVs on chromosome 14 (34.75% of the total number of variants) indicates a possible uniqueness within the Croatian population, while benign variants on chromosomes 13, 18 and 20 are almost absent. The distribution of duplications (72.55%) among 2288 variants is significantly more prevalent than deletions (27.45%). Benign variants encompassing segments or entire genes whose specific alleles are assocaited with different diseases (so called morbid genes) like FCGR3A, ATF6, TFG, NIPA1, TAP2, KANSL1 underscore the existence of non-clinically significant variations in coding and regulatory regions of the human genome. This registry represents an important resource not only for diagnostic purposes but also for future research on genomic variability in the Croatian population, providing a systematic insight into benign CNVs.Varijante broja kopija (CNV) označavaju delecije ili duplikacije DNA veličine od 50 parova baza (bp) do nekoliko megabaza (Mb). Klinički značaj CNV-ova klasificira se prema smjernicama Američkog sveučilišta medicinske genetike i genomike. Benigne varijante broja kopija su raširene u općoj populaciji i nemaju kliničkog značaja. U okviru ovog istraživanja provela se retrospektivno-prospektivna analiza kod 400 pacijenata upućenih na dijagnostičku obradu radi različitih tipova neurorazvojnih poremećaja, u razdoblju od rujna 2021. do svibnja 2023. U sklopu istraživanja napravljen je registar benignih CNV-ova hrvatske populacije. Značajno veća učestalost benignih CNV-ova na kromosomu 14 (34.75% od ukupnog broja varijanti) ukazuje na moguću jedinstvenost unutar hrvatske populacije, dok su benigne varijante na kromosomima 13, 18 i 20 gotovo u potpunosti odsutne. Distribucija duplikacija (72,55%) među 2288 varijanti značajno prevladava u odnosu na delecije (27,45%). Benigne varijante koje sadržavaju dio ili cijele gene, čiji su specifični aleli povezani s različitim bolestima (tzv. morbidni geni) poput FCGR3A, ATF6, TFG, NIPA1, TAP2, KANSL1, pokazuju da unutar ljudskog genoma postoje različite varijante u kodirajućim i regulacijskim regijama koje nemaju klinički značaj. Ovaj registar predstavlja važan resurs ne samo za dijagnostičke svrhe već i za buduća istraživanja genomske varijabilnosti u hrvatskoj populaciji, pružajući povezan i sustavan uvid u benigne CNV-ove
Inhibition of human cholinesterases by O-alkyloximes
No full textAcetilkolinesteraza (AChE) i butirilkolinesteraza (BChE) su enzimi koji kataliziraju hidrolizu acetilkolina i njihova inhibicija jedna je od glavnih strategija u liječenju Alzheimerove bolesti (AB). No, budući da je AB multifaktorijalna bolest, noviji pristup liječenju je razvoj lijekova s višestrukim učinkom koji bi istovremeno djelovali na više mogućih uzročnika bolesti. U sklopu ovog diplomskog rada testirano je 20 O-alkiloksima kao inhibitora ljudskih AChE i BChE, a za nekolicinu spojeva procijenjena je sposobnost vezanja u periferno mjesto AChE i sposobnost inhibicije β-amiloidne samoagregacije. Svi ispitani spojevi reverzibilno su inhibirali obje kolinesteraze u mikromolarnom području, s konstantama inhibicije Ki u rasponu 0,30 – 360 μmol dm–3. Najjačim inhibitorom AChE pokazao se spoj 20 (Ki = 6 μmol dm–3), dok je BChE najjače inhibirao spoj 15 (Ki = 0,30 μmol dm–3). Gotovo svi ispitivani O-alkiloksimi pokazali su se selektivnim inhibitorima BChE u odnosu na AChE. Sposobnost vezanja u periferno mjesto AChE i moguće sprječavanje nastajanja neurotoksičnog kompleksa AChE-β-amiloid pokazali su spojevi 2, 18, 19 i 20. Kao inhibitori β-amiloidne samoagregacije istaknuli su se spojevi 18 i 20. Za sve spojeve je in silico procijenjena sposobnost prolaska kroz krvno-moždanu barijeru te je pokazano da bi mogli prijeći krvno-moždanu barijeru pasivnim transportom.Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are enzymes that catalyze the hydrolysis of acetylcholine, and their inhibition is one of the main strategies in the treatment of Alzheimer's disease (AD). But, AD is a multifactorial disease so a new approach to treatment is development of multi-target directed ligands that would simultaneously act on several possible causes of the disease. As part of this thesis, 20 O-alkyloximes were tested as inhibitors of human AChE and BChE, and some of them were also tested for ability to bind to the peripheral site of AChE and to inhibit β-amyloid self-aggregation. All tested compounds reversibly inhibited both cholinesterases with inhibition constants Ki in the range of 0,30 – 360 μmol dm–3. The most potent AChE inhibitor was compound 20 (Ki = 6 μmol dm–3), while that of BChE was compound 15 (Ki = 0,30 μmol dm–3). Tested O-alkyloximes were generally more selective inhibitors of BChE than of AChE. Compounds 2, 18, 19 and 20 showed the ability to bind to the peripheral site of AChE and possible attenaution of formation of the neurotoxic AChE-β-amyloid complex. Compounds 18 and 20 proved to inhibit β-amyloid self-aggregation. All compounds were evaluated in silico for ability to pass the blood-brain barrier and all of them should be able to pass the blood-brain barrier by passive transport
Gamma-radiolytic degradation of loratadine in water
No full textLoratadin je antihistaminik koji se zbog česte upotrebe može pojaviti u otpadnim vodama što predstavlja rastući rizik za okoliš. Primjena ionizirajućeg zračenja pokazala se kao dobra alternativna metoda pročišćavanja otpadnih voda. U ovom radu provedena je razgradnja loratadina primjenom gama-zračenja. Utjecaj brzine i doze zračenja, te prisutnost različitih anorganskih soli i hvatača radikala na učinkovitost razgradnje određena je tekućinskom kromatografijom visoke djelotvornosti. Razgradni produkti analizirani su vezanim sustavom tekućinske kromatografije ultravisoke djelotvornosti i spektrometrije masa visokog razlučivanja. Na temelju MS i MS/MS spektara predložene su njihove strukture i razgradni put loratadina.Loratadine is an antihistamine which, because of the frequent use, can be found in wastewater, presenting a growing environmental risk. Ionizing radiation was found to be an effective alternative wastewater purification method. In this work degradation of loratadine by gamma irradiation was performed. The efficiency of degradation at different radiation rates and doses, in the presence of various inorganic salts and radical scavengers was investigated by high performance liquid chromatography. The degradation products were analysed by ultra high-performance liquid chromatography coupled to high-resolution mass spectrometry. Structures of degradants and degradation pathway of loratadine were proposed based on obtained results
Microclimatic features of the cave Golubnjača in Plitvice Lakes National Park
No full textU diplomskom radu su prikupljeni i analizirani podaci o mikroklimi špilje Golubnjače u NP Plitvička jezera. Do 1991. godine Golubnjača je bila turistička špilja. Podaci su prikupljeni memorijskim termohidrografima, anemometrom te logerom za koncentraciju ugljikovog dioksida. Mikroklimatski parametri su mjereni 2022. i 2023. godine. Analizirani su i podaci o antropogenom utjecaju u špilji tijekom radionice restauriranja. Svrha mjerenja bila je odrediti na koji način se mikroklima u podzemlju mijenja i zašto te što i kako utječe na promjene koje se događaju.The thesis collects and analyses data on the microclimate of the Golubinjača cave, which is located in the Plitvice Lakes National Park. Until 1991, the cave was used for tourism. Data were collected with memory thermohydrographs, anemometer, and carbon dioxide concentration logger. Microclimatic parameters were measured in 2022 and 2023. Moreover, the data on the anthropogenic impact on the cave during the restoration workshop was also analysed. The purpose is to determine how the microclimate of Golubnjača is changing and why as well as what affects the changes that occur and how
Characterisation of silicon dioxide nanoparticles of different sizes and their modification by polyelectrolyte
No full textNanočestice silicijeva dioksida pokazuju veliki potencijal za primjenu u raznim područjima te je za njihovu primjenu važno razumjeti kako veličina utječe na njihova ostala svojstva. Nadalje, modificiranjem nanočestica adsorpcijom polielektrolita moguće je promijeniti njihova svojstva. Polielektroliti su makromolekule čije podjedinice sadrže ionske ili lako ionizirajuće skupine te ih je moguće adsorbirati na površine suprotnog naboja. U ovome radu istražen je utjecaj veličine nanočestica silicijeva dioksida na njihova svojstva te su korištene čestice promjera od 10 nm do 100 nm. Veličina čestica određena je mikroskopijom atomskih sila te pretražnom elektronskom mikroskopijom. Dinamičkim i elektroforetskim raspršenjem svjetlosti određeni su hidrodinamički promjer i ζ-potencijal nanočestica pri različitim koncentracijama natrijeva klorida. Površinski naboj određen je titracijom nanočestica otopinom polielektrolita. Zatim je na nanočestice adsorbiran poli(N-etil-4-vinilpiridinijev) bromid te je određeno kako maksimalna koncentracija polielektrolita ovisi o veličini čestica. Također su određeni veličina čestica, hidrodinamički promjer te ζ-potencijal i uspoređeni s nemodificiranim česticama.Silicon dioxide nanoparticles show great potential for application so it’s important to understand how their size affects their other properties. It is possible to modify nanoparticle properties my adsorbing polyelectrolytes on them. Polyelectrolytes are macromolecules which contain ionic or easily ionisable groups, and they can be adsorbed on oppositely charges surfaces. The influence of silicon dioxide nanoparticle size on their properties was studied for nanoparticles with a diameter of 10 nm to 100 nm. Particle size was determined by atomic force microscopy and scanning electron microscopy. Dynamic and electrophoretic light scattering was used to determine the hydrodynamic radius and ζ-potential of the particles at different concentrations of sodium chloride. Surface charge was determined by titrating nanoparticles with polyelectrolyte. Then, poly(N-ethyl-4-vinylpyridinium) bromide was adsorbed and the dependence of maximum polyelectrolyte concentration on particle diameter was shown. Particle size, hydrodynamic radius and ζ-potential were also determined and compared to unmodified particles
Inhibitory effects of antibiotics and the deletion of morfogenetic genes on pseudomurein synthesis in Methanothermobacter thermautotrophicus
No full textMethanogenic archaea have recently gained attention thanks to their environmental significance and role in human microbiota. Some of them build their cell walls with pseudomurein, structural analog of bacterial murein, but the mechanisms behind its biosynthesis and regulation remain understudied. This thesis explores archaeal peptidoglycan through two complementary approaches. I tested the sensitivity of Methanothermobacter thermautotrophicus, an archaea with peptidoglycan, to cell-wall targeting antibiotics (bacitracin, gardymicin, enduracidin and nisin). I also utilized the first genetic manipulation tool developed for this organism, based on interdomain conjugation with bacteria Escherichia coli, to delete the genes (mreB, mbaP, rodA) potentially involved in morphogenesis. M. thermautotrophicus was sensitive to all tested antibiotics, with minimal inhibitory concentration similar to those observed in bacteria. Nisin, gardymicin and enduracidin induced cell deformations at their half maximal inhibitory concentration. Although mutations of morphogenetic genes mreB, mbaP and rodA were not confirmed in this research, significant phenotypic differences in comparison to wild type, such as altered cell dimensions, suggest the involvement of these genes in cell elongation. This research optimizes and establishes methods for peptidoglycan biology studies on M. thermautotrophicus, providing a foundation for further investigation of this unique cell wall structure of methanogens.Metanogene arheje u posljednje vrijeme privlače pažnju zbog svoje ekološke važnosti i uloge u sastavu ljudske mikrobiote. Neke od njih svoje stanične stijenke izgrađuju od pseudomureina, strukturnog analoga bakterijskog mureina, no mehanizmi njegove biosinteze i regulacije kod arheja još uvijek su nedovoljno istraženi. Ovaj rad istražuje arhealni peptidoglikan kroz dva komplementarna pristupa. Testirala sam osjetljivost Methanothermobacter thermautotrophicus, arheje koja sadrži peptidoglikan, na antibiotike koji cilјaju staničnu stijenku (bacitracin, gardimicin, enduracidin i nisin). Također, koristila sam prvi alat za genetsku manipulaciju razvijen za ovu vrstu, temeljen na interdomenskoj konjugaciji s bakterijom Escherichia coli, kako bih uništila gene (mreB, mbaP, rodA) potencijalno uključene u morfogenezu. Methanothermobacter thermautotrophicus je bio osjetljiv na sve testirane antibiotike, s minimalnom inhibitornom koncentracijom sličnom onoj kod bakterija. Nisin, gardimicin i enduracidin inducirali su deformacije oblika stanica pri polovini maksimalne inhibitorne koncentracije. Iako mutacije morfogenetskih gena mreB, mbaP, rodA treba još potvrditi, značajne fenotipske razlike u odnosu na divlji tip, poput promjena staničnih dimenzija, upućuju na sudjelovanje tih gena u dinamici stanične elongacije. Provedeno istraživanje optimizira i uspostavlja metode za istraživanje biologije peptidoglikana na arheji M. thermautotrophicus, pružajući temelj za daljnje istraživanje ove jedinstvene stanične stijenke metanogena
Effect of copper oxide nanoparticles on oxidative stress in the freshwater alga Chlorella vulgaris
No full textBakar je važan metal sve zastupljeniji u obliku nanomaterijala u svakodnevnom životu. Intenzivna proizvodnja i korištenje materijala koji sadrže nanočestice bakra dovodi do otpuštanja tih čestica u okoliš što predstavlja potencijalnu opasnost za žive organizme zbog njihove visoke reaktivnosti i toksičnosti. Zelena alga Chlorella vulgaris je uvriježeni modelni organizam u ekotoksikološkim istraživanjima. U svom diplomskom radu analizirao sam utjecaj nanočestica CuO i Cu2O te iona bakra (CuSO4) u koncentracijama koje omogućuju preživljenje stanica alge C. vulgaris od 75% nakon 72 sata. Rezultati pokazuju da su nanočestice i ioni bakra značajno povećali razine reaktivnih oblika kisika, što je narušilo integritet biomembrana, dok su nanočestice CuO dodatno izazvale oštećenje proteina u stanicama. Nanočestice bakra nisu značajno utjecale na promjenu aktivnosti antioksidacijskih enzima, dok je ionski bakar značajno inhibirao njihovu aktivnost. Sadržaj reduciranog glutationa se povećao, a razina prolina smanjila nakon svih tretmana što ukazuje na pojačanu pripremu, ali i na kontinuiranu obranu stanica od oksidacijskog stresa. Nakon svih tretmana, ekspresija proteina Hsp70 se nije promijenila, dok se ekspresija proteina Hsp90 značajno smanjila. Izražena plazmoliza i destabilizacija stanične stijenke i membrane prati sve tretmane. Nanočestice CuO i Cu2O nakupljaju se na stanicama alge, u vakuoli te na tilakoidnim membranama. Tretmani s nanočesticama bakra imaju fitotoksičniji učinak na stanice alge u odnosu na tretman ionima bakra. Nanočestice Cu2O bile su fitotoksičnije na stanice alge u odnosu na nanočestice CuO.Copper is an important metal that is increasingly present in everyday life in the form of nanomaterials. The intensive production and use of materials containing copper nanoparticles leads to the release of these particles into the environment, posing a potential risk to living organisms due to their high reactivity and toxicity. The green alga Chlorella vulgaris is an established model organism in ecotoxicological research. In my master thesis, I investigated the influence of CuO and Cu2O nanoparticles and copper ions (CuSO4) in concentrations that enable 75% of the algal cells of C. vulgaris to survive after 72 hours. The results show that copper nanoparticles and ions significantly increase the level of reactive oxygen species, that damage the integrity of biomembranes, while CuO nanoparticles additionally cause protein damage in the cells. Copper nanoparticles had no significant effect changing the activity of antioxidant enzymes, while ionic copper significantly inhibited their activity. Reduced glutathione levels increased, and proline levels decreased after all treatments, indicating improved priming but also continuous defense of cells against oxidative stress. After all treatments, the expression of the Hsp70 protein did not change, while the expression of the Hsp90 protein decreased significantly. Pronounced plasmolysis and destabilization of the cell wall and membrane were observed after all treatments. CuO and Cu2O nanoparticles accumulate on algal cells, in the vacuole and on thylakoid membranes. Copper nanoparticle treatments have a more toxic effect on algal cells compared to copper ions. Cu2O nanoparticles were more phytotoxic to algal cells compared to CuO nanoparticles
Gamma-radiolytic degradation of nabumetone in water
No full textNabumeton je jedan od nesteroidnih lipofilnih protuupalnih lijekova. Farmakološko djelovanje ostvaruje putem metabolita 6-metoksi-2-naftiloctene kiseline, koji je inhibitor enzima ciklooksigenaze. Međudjelovanjem ionizirajućeg zračenja i tvari nastaju reaktivne kratkoživuće čestice, oksidirajuće i reducirajuće vrste, koje neselektivnim reakcijama reagiraju s farmaceuticima te ih mogu prevesti u za okoliš neškodljive produkte. U sklopu ovog diplomskog rada, za kvantitativno određivanje nabumetona korištena je tekućinska kromatografija visoke djelotvornosti i UV/Vis spektrofotometrija. Djelotvornost razgradnje praćena je u vodenim otopinama pri različitim koncentracijama nabumetona, različitim dozama zračenja te različitim vrijednostima pH. Također, praćen je i utjecaj različitih "hvatača" radikala, anorganskih iona te otapala. Spregnuti sustav tekućinske kromatografije ultravisoke djelotvornosti i spektrometrije masa visokog razlučivanja korišten je za analizu razgradnih produkata nabumetona. Na temelju rezultata analize tandemnom spektrometrijom masa, pretpostavljene su strukture i sheme fragmentacije razgradnih produkata nabumetona.Nabumetone is one of the non-steroidal anti-inflammatory drugs, characterized by its non-acidic and lipophilic properties. Its pharmacological effects are achieved through the metabolite 6-methoxy-2-naphthylacetic acid, which is an inhibitor of the cyclooxygenase enzyme. Interaction of ionizing radiation and the substance results in the formation of reactive short- lived particles, oxidizing and reducing species, which, through non-selective reactions, react with pharmaceuticals and can transform them into environmentally benign products. In this work, high performance liquid chromatography and UV/Vis spectrophotometry were used for the quantification of nabumetone. The degradation efficiency was monitored in aqueous solutions at different initial concentrations of nabumetone, different radiation doses, and different pH values. Additionally, the impact of various radical scavengers, inorganic ions, and solvents was observed. A coupled system of ultra-high-performance liquid chromatography and high-resolution mass spectrometry was used for the analysis of nabumetone degradation products. Based on the results of tandem mass spectrometry analysis, structures and fragmentation schemes of nabumetone degradants were proposed
Assessment of data quality for drought index insurance in Eastern Croatia
No full textSve češći i nepredvidljiviji vremenski ekstremi otežavaju razvoj poljoprivrede. Nove tehnologije detekcije, promatranja usjeva i osiguranja pomažu poljoprivrednicima suzbiti financijske štete načinjene vremenskim nepogodama. Razvitkom novih poljoprivrednih tehnologija, ukazuje se potreba za uvođenjem nove vrste osiguranja. Indeksno osiguranje koje koristi metode daljinskih istraživanja u cilju bržeg, efikasnijeg i preciznijeg mjerenja štete na usjevima. Istraživanje se bavi procjenom kvalitete dostupnih podataka za njegovu izradu na području Istočne Slavonije. Rezultati su pokazali kako, na temelju dostupnih podataka, od promatranih usjeva samo pšenica ima uvijete za izradu indeksnog osiguranja.Increasingly frequent and unpredictable weather extremes are affecting the development of agriculture. New technologies for monitoring, observing and insuring crops are helping farmers to minimise the financial losses caused by weather disasters. A new type of insurance is emerging – index-based insurance that uses remote sensing methods to measure crop damage more quickly, efficiently and accurately. The research focuses on assessing the quality of available data for its development in the Eastern Slavonia region. The results have shown that, based on the available data, only wheat among the observed crops fulfils the conditions for the development of index-based insurance