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REDOX PROPERTIES OF FREE AMINO ACIDS AND INDOLE AS A MODEL COMPOUND IN THE FENTON SYSTEM

dc.contributor.advisorAnđelković, Katarina
dc.contributor.advisorBogdanović Pristov, Jelena
dc.contributor.otherSladić, Dušan
dc.creatorMilić Komić, Sonja
dc.date.accessioned2024-04-16T08:05:58Z
dc.date.available2024-04-16T08:05:58Z
dc.date.issued2018
dc.identifier.urihttp://rimsi.imsi.bg.ac.rs/handle/123456789/3191
dc.description.abstractU ovoj tezi ispitivane su antioksidativne aktivnosti (AA) slobodnih aminokiselina (glicin, alanin, prolin, valin, izoleucin, leucin, fenilalanin, triptofan, tirozin, serin, treonin, asparagin, glutamin, histidin, asparaginska kiselina, glutaminska kiselina, lizin, arginin, cistein i metionin, homocistein, hidroksiprolin, norleucin, 2-aminobutanska kiselina i 3,4-dihidroksifenilalanin) u Fentonovom sistemu. Redosled reaktivnosti aminokiselina u reakciji sa hidroksil-radikalom, antioksidativne aktivnosti (HO• ) bio je sledeći: Trp > norleucin > Phe, Leu > Ile > His >3,4-dihidroksifenilalanin, Arg > Val > Lys, Tyr, Pro > hidroksiprolin > α-aminobutanska kiselina > Gln, Thr, Ser > Glu, Ala, Gly, Asn, Asp. Aminokiseline koje sadrže sumpor su u reakciji sa hidroksil-radikalom davale više različitih radikalskih vrsta koje su ispitivane EPR metodom sa spinskim hvatačima. Korelaciona analiza dobijenih eksperimentalnih podataka sa literaturno poznatim parametrima koji karakterišu različite osobine slobodnih aminokiselina je pokazala pozitivnu korelaciju između AA i hidrofobnosti. Kada se podele aminokiseline (AK), kod nenaelektrisanih aminokiselina je uočena vrlo jaka korelacija sa hidrofobnošću. Kod naelektrisanih AK se ne primećuje korelacija, ili je korelacija negativna, zavisno od primenjene skale parametara. Jaka negativna korelacija je nađena kod AA i polarnosti. Sterni parametri i hidratacioni brojevi su pokazali pozitivnu korelaciju AA sa AK sa nepolarnim bočnim lancem. Smanjenje temperature koje podstiče hidrofobnu hidrataciju je uzrokovalo povećane vrednosti AA, što ukazuje na to da je oksidacija AK sa HO• zavisna od hidrofobne hidratacije. Ova istraživanja se mogu primeniti u procesima prečišćavanja prirodnih i otpadnih voda, s obzirom na to da AK ulaze u sastav prirodnog organskog materijala. Aminokiselina sa najvećom vrednošću za antioksidativnu aktivnost je bila triptofan u reakciji sa HO• u Fentonovom sistemu. U cilju boljeg razumevanja reaktivnosti triptofana i njegovih derivata, odabran je indol kao model-jedinjenje za dalje ispitivanje interakcija aromatičnih aminokiselina. Interakcije gvožđa i organskih supstanci su prisutne u mnogim aspektima iii zaštite životne sredine, uključujući foto-redoks reakcije, recikliranje i dostupnost gvožđa. U ovoj tezi ispitivane su redoks reakcije gvožđa i indola u vodi u prisustvu UV-zračenja. Prisustvo jednog molekula indola dovelo je do prisustva osam jona redukovanog gvožđa, bez doprinosa direktne redukcije Fe3+ pod uticajem svetlosti, koja daje Fe2+ i HO• kao proizvode reakcije. Glavni mehanizmi koji dovode do redukcije Fe(III) u prisustvu indola, tj. akumulacije Fe(II) su: hvatanje slobodnog radikala HO• , što sprečava oksidaciju Fe(II) sa HO• ; oksidacija indola i njegovih derivata sa ekscitovanim gvožđem; redukcija gvožđa sa ekscitovanim indolom (kod UV-A zračenja nije prisutno). Hidratisani elektroni nemaju veliku ulogu u redukciji Fe. Radikali indola su primećeni kao nusproizvodi u interakcijama indola i gvožđa. Kompleks niske simetrije indola i Fe3+ je potvrđen primenom EPR metode. Formiranje kompleksa potpomaže transfer elektrona sa ekscitovanog indola na Fe3+. Ova istraživanja su važna za razumevanje procesa foto-redukcije gvožđa sa heterocikličnim aromatičnim zagađivačima i unapređenje protokola za prečišćavanje indola u otpadnim vodama.sr
dc.description.abstractIn this thesis antioxidative activities (AA) of free L-amino acids (glycine, alanine, proline, valine, isoleucine, leucine, phenylalanine, tryptophane, tyrosine, serine, threonine, asparagine, glutamine, histidine, aspartic acid, glutamic acid, lysine, arginine, cystein and methionine, homocysteine, hydroxyproline, norleucine, α-aminobutyric acid and 3,4-dihydroxyphenylalanine) against Fenton system-mediated hydroxyl radical (HO• ) production in aqueous solution were studied. The rank order according to AA was: Trp > norleucine > Phe, Leu > Ile > His >3,4-dihydroxyphenylalanine, Arg > Val > Lys, Tyr, Pro > hydroxyproline> α-aminobutyric acid > Gln, Thr, Ser > Glu, Ala, Gly, Asn, Asp. Sulfurcontaining FAA generated different secondary reactive products, which were discriminated by the means of electron paramagnetic resonance spin-trapping spectroscopy. Correlation analysis between experimental data and a set of physicochemical parameters known from available literature showed positive correlation with hydrophobicity. When taken separately, uncharged FAA exhibited strong positive correlation of AA with hydrophobicity whereas charged FAA showed negative or no significant correlation depending on the scale applied. A general strong negative correlation was found between AA and polarity. Steric parameters and hydration numbers correlated positively with AA of nonpolar side-chain FAA. Decrease of temperature which promotes hydrophobic hydration resulted in increased AA, which implies that HO• -provoked oxidation of FAA is strongly affected by hydrophobic hydration. Our findings are important for the understanding of oxidation processes in natural and waste waters, considering the amount of amino acids in natural organic material. Amino acid with the highest value for AA in the reaction with HO• in Fenton system was tryptophan. With the goal of better understanding of the reactivity of tryptophan and it’s derivatives indole was chosen as a model compound for further examination of interactions of aromatic amino acids. Iron–organic substances interactions are involved in a variety of environmental phenomena, including photo-redox reactions, iron cycling and bioavailability, v as well as contaminant fate. In this thesis UV-induced redox reactions of iron and indole in water were examined. The presence of one indole molecule in the irradiated system resulted in the presence of eight reduced ferric ions, not counting direct reduction of Fe3+ in the presence of light, which gives Fe2+ and hydroxyl radical (HO• ) as products. The main mechanisms that contribute to indole-related Fe3+ reduction i.e. Fe2+ accumulation are: (i) HO• scavenging, which prevents oxidation of Fe2+ by HO• ; (ii) oxidation of indole and its derivatives by excited ferric iron; (iii) reduction of ferric iron by excited indole (not present under UV-A). Hydrated electrons released by UV-B-excited indole play only a minor role in the reduction of iron. Indole-derived radicals emerged as byproducts of indole/iron photochemistry. Low-T EPR spectroscopy showed that indole forms a weak low-symmetry complex with Fe3+. The formation of complex promotes electron transfer from excited indole to Fe3+. Our findings are important for understanding the catalysis of photo-reduction of iron by heterocyclic aromatic pollutants, and for the development of protocols for indole processing in wastewaters.sr
dc.language.isosrsr
dc.relationinfo:eu-repo/grantAgreement/MESTD/Integrated and Interdisciplinary Research (IIR or III)/43010/RS//sr
dc.rightsopenAccesssr
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.sourceУниверзитет у Београду, Хемијски факултетsr
dc.subjectslobodne aminokiseline / triptofan / indol / redoks osobine / antioksidativnost / Fentonov sistem / hidroksil-radikal / gvožđe / otpadne vode / UV zračenje / free amino acids / tryptophan / indole / redox properties / antioxidant / Fenton system / hydroxyl radical / iron / waste waters / UV irradiationsr
dc.titleREDOKS SVOJSTVA SLOBODNIH AMINOKISELINA I INDOLA KAO MODELJEDINJENJA U FENTONOVOM SISTEMUsr
dc.titleREDOX PROPERTIES OF FREE AMINO ACIDS AND INDOLE AS A MODEL COMPOUND IN THE FENTON SYSTEMsr
dc.typedoctoralThesissr
dc.rights.licenseBYsr
dc.identifier.fulltexthttp://rimsi.imsi.bg.ac.rs/bitstream/id/8599/bitstream_8599.pdf
dc.identifier.rcubhttps://hdl.handle.net/21.15107/rcub_rimsi_3191
dc.type.versionpublishedVersionsr


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