Zinc(II) and cadmium(II) complexes of N-terminally free peptides containing two separate cysteinyl binding sites

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Physico-chemical properties of MnII complexes formed with cis- and trans-DO2A: thermodynamic, electrochemical and kinetic studies

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The Portrait of the Artist as an Irish Woman: The Figure of Helen in Jennifer Johnston's The Railway Station Man

Jennifer Johnston is (1930- ) a prominent contemporary Irish writer, the author of short stories, television scripts and plays for the theatre, although her reputation mainly rests on her novels. By using female protagonists in the majority of her novels, she directs the readers’ attention to women’s positions and their opportunities in the country. (Introduction)egyetemiangol nyelv és irodalo

Coordination and redox properties of transition metal complexes of peptides and peptide derivatives

Doktori munkám során olyan réz(II)komplexek vizsgálatával foglalkoztam, amelyek az eukarióták sejtjeiben működő Cu,Zn-szuperoxid-diszmutáz enzim aktív centrumát modellezik. A vizsgált ligandumok egyik csoportját a több hisztidint tartalmazó peptidek adták, a másik csoportba a kelátképző helyzetben két imidazolnitrogént tartalmazó bisz(imidazol-2-il) származékok tartoztak. A több hisztidint tartalmazó ligandumok esetében nikkel(II)- és kobalt(II)ionok jelenlétében vizsgáltuk a komplexképző sajátságokat. Ezt követően a több hisztidint tartalmazó peptidek és a bisz(imidazol-2-il) származékok azon Cu(II)-komplexeinek redoxipotenciál értékeit mértük meg ciklikus voltammetria segítségével, amelyekben a fémion imidazolnitrogéneken keresztül koordinálódik a ligandumhoz. A munka harmadik szakaszában a szerkezeti és redoxi szempontból ígéretesnek bizonyuló Cu(II)-komplexek SOD-aktivitását határoztuk meg indirekt fotometriás technikával. Eredményeink azt mutatják, hogy két komplex: a négy imidazolkoordinációjú, HXH szekvenciát tartalmazó multihisztidin peptid [CuL]2+ komplexe és a Cu(II)-His-BIMA rendszerben képződő, hárommagvú imidazolátohidas [Cu3L2H 4]2+ komplex is jelentős SOD-aktivitással rendelkezik. During my Ph.D. work I studied such Cu(II) complexes that mimic the active site of Cu,Zn superoxide dismutase enzyme. One group of the studied ligands includes multihistidine peptides, the other group consists of those derivatives of bis(imidazol-2-yl)methane that contain two imidazole nitrogen atoms in chelatable position. In the case of the multihistidine peptides, we studied the complex formation processes in the presence of nickel(II) and cobalt(II) ions. Afterwards we measured the redox potential values of those Cu(II) complexes of multihistidine peptides and bis(imidazol-2-yl) derivatives in which the metal ion is bound to the ligand through imidazole nitrogens. In the third phase of the work, we determined the SOD activity of the Cu(II) complexes that seemed to be promising SOD models both from a structural and a redox point of view. Our results reflect that two of the studied Cu(II) complexes exhibit significant SOD activity: the four imidazole nitrogen coordinated [CuL]2+ complex of the multihistidine peptide containing the HXH sequence and the imidazolato bridged [Cu3L2H 4]2+ complex that is formed in the Cu(II)-His-BIMA system

VO²⁺ complexation by bioligands showing keto–enol tautomerism: a potentiometric, spectroscopic, and computational study

The interaction of VO2+ ion with ligands of biological interest that are present in important metabolic pathways—2-oxopropanoic acid (pyruvic acid, pyrH), 3-hydroxy-2-oxopropanoic acid (3-hydroxypyruvic acid, hydpyrH), oxobutanedioic acid (oxalacetic acid, oxalH2), (S)-hydroxybutanedioic acid (l-malic acid, malH2), and 2,3-dihydroxy-(E)-butanedioic acid (dihydroxyfumaric acid, dhfH2)—was described. Their complexing capability was compared with that of similar ligands: 3-hydroxy-2-butanone (hydbut) and 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, squarH2). All of these ligands (except l-malic acid) exhibit keto–enol tautomerism, and the presence of a metal ion can influence such an equilibrium. The different systems were studied with electron paramagnetic resonance (EPR) and UV–vis spectroscopies and with pH potentiometry. Density functional theory (DFT) methods provide valuable information on the relative energy of the enol and keto forms of the ligands both in the gas phase and in aqueous solution, on the geometry of the complexes, and on EPR and electronic absorption parameters. The results show that most of the ligands behave like α-hydroxycarboxylates, forming mono- and bis-chelated species with (COO–, O–) coordination, demonstrating that the metal ion is able to stabilize the enolate form of some ligands. With dihydroxyfumaric acid, the formation of a non-oxidovanadium(IV) complex, because of rearrangement of dihydroxyfumaric to dihydroxymaleic acid (dhmH2), can be observed. With 3-hydroxy-2-butanone and 3,4-dihydroxy-3-cyclobutene-1,2-dione, complexation of VO2+ does not take place and the reason for this behavior is explained by chemical considerations and computational calculations