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1.

001-es BibID:BIBFORM084872
Első szerző:Bauer-Siebenlist, Bernhard
Cím:Correlation of Structure and Function in Oligonuclear Zinc(II) Model Phosphatases / Bernhard Bauer-Siebenlist, Franc Meyer, Etelka Farkas, Denis Vidovic, Jose Antonio Cuesta-Seijo, Regine Herbst-Irmer, Hans Pritzkow
Dátum:2004
ISSN:0020-1669 1520-510X
Megjegyzések:A series of pyrazolate-based dizinc(II) complexes has been synthesized and investigated as functional models for phosphoesterases, focusing on correlations between hydrolytic activity and molecular parameters of the bimetallic core. The Zn···Zn distance, the (bridging or nonbridging) position of the Zn-bound hydroxide nucleophile, and individual metal ion coordination numbers are controlled by the topology of the compartmental ligand scaffold. Species distributions of the various dizinc complexes in solution have been determined potentiometrically, and structures in the solid state have been elucidated by X-ray crystallography. The hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) promoted by the dinuclear phosphoesterase model complexes has been investigated in DMSO/buffered water (1:1) at 50 °C as a function of complex concentration, substrate concentration, and pH. Coordination of the phosphodiester has been followed by ESI mass spectrometry, and bidentate binding could be verified crystallographically in two cases. Drastic differences in hydrolytic activity are observed and can be attributed to molecular properties. A significant decrease of the pKa of zinc-bound water is observed if the resulting hydroxide is involved in a strongly hydrogen-bonded intramolecular O2H3 bridge, which can be even more pronounced than for a bridging hydroxide. Irrespective of the pKa of the Zn-bound water, a hydroxide in a bridging position evidently is a relatively poor nucleophile, while a nonbridging hydroxide position is more favorable for hydrolytic activity. Additionally, the metal array has to provide a sufficient number of coordination sites for activating both the substrate and the nucleophile, where phosphate diesters such as BNPP preferentially bind in a bidentate fashion, requiring a third site for water binding. Product inhibition of the active site by the liberated (p-nitrophenyl)phosphate is observed, and the product-inhibited complex could be characterized crystallographically. In that complex, the phosphate monoester is found to cap a rectangular array of four zinc ions composed of two bimetallic entities.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry. - 43 : 14 (2004), p. 4189-4202. -
További szerzők:Meyer, Franc Farkas Etelka (1948-) (vegyész) Vidovic, Denis Cuesta-Seijo, Jose Antonio Herbst-Irmer, Regine Pritzkow, Hans
Pályázati támogatás:OTKA TS 040685
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2.

001-es BibID:BIBFORM112584
035-os BibID:(WoS)000180272100003 (Scopus)0037294304
Első szerző:Farkas Etelka (vegyész)
Cím:New insight into the oxidation of Fe(II) by desferrioxamine B (DFB): spectrophotometric and capillary electrophoresis (CE) study / E. Farkas, É.A. Enyedy, I. Fábián
Dátum:2003
ISSN:1387-7003
Megjegyzések:Results on the previously described irreversible redox reaction taking place between iron(II) and desferrioxamine B (DFB) under anaerobic conditions have been complemented by additional capillary electrophoresis (CE) and kinetic studies in the present work. Reduction of the oxidizing agent, DFB to monoamide derivative, was confirmed by CE technique and suggestion for the most probable kinetically active species and mechanism of the initial step is discussed in the paper.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry Communications. - 6 : 2 (2003), p. 131-134. -
További szerzők:Enyedy Éva Anna (1975-) (vegyész) Fábián István (1956-) (vegyész)
Pályázati támogatás:034674
OTKA
040685
OTKA
028244
OTKA
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3.

001-es BibID:BIBFORM084891
Első szerző:Farkas Etelka (vegyész)
Cím:Carbamoylphosphonate-based matrix metalloproteinase inhibitor metal complexes: solution studies and stability constants. Towards a zinc-selective binding group / Etelka Farkas, Yiffat Katz, Sudhakar Bhusare, Reuven Reich, Gerd-Volker Röschenthaler, Martin Königsmann, Eli Breuer
Dátum:2004
ISSN:0949-8257
Megjegyzések:Overactive matrix metalloproteinases (MMPs) are associated with a variety of disease states. Therefore, their inhibition is a highly desirable goal. Yet, more than a decade of worldwide activity has not produced even one clinically useful inhibitor. Because of the crucial role of zinc in the activity of the enzyme, the design of inhibitors is usually based upon a so-called zinc binding group (ZBG). Yet, many of the hitherto synthesized potent inhibitors failed clinically, presumably because they bind stronger to metals other than zinc. We have developed in vivo potent inhibitors based on the carbamoylphosphonic group as a putative ZBG. In this paper we report stability constants for Ca(II), Mg(II), Zn(II) and Cu(II) complexes of two potent, in vivo active, MMP inhibitors, cyclopentylcarbamoylphosphonic acid (1) and 2-(N,N-dimethylamino)ethylcarbamoylphosphonic acid (2). Precipitation prevented the determination of stability constants for iron(III) complexes of 1 and 2. For comparison with carbamoylphosphonates 1 and 2, we synthesized 2-cyclohexyl-1,1-difluoroethylphosphonic acid (3), which does not inhibit MMP, and determined the stability constants of its complexes with Mg(II), Ca(II) and Zn(II). Comparison with the values obtained from the complexes of 1 and 2 with those from 3 indicates participation of the C=O group in the metal binding of the former compounds. The complex stability orders for both 1 and 2 are Ca(II)<Mg(II)<Zn(II)<- Cu(II). In addition, the results indicate that at pH>8 the dimethylamino group of compound 2 can also participate in the binding of the transition metals Cu and Zn. On the other hand, the amino group in carbamoylphosphonic acid 2 lowers the stability of the complexes with metals favoring oxygen ligands (Ca, Mg and Fe) and increases the selectivity towards Zn. These results are helpful for rationalizing the results observed on our MMP inhibitors hitherto examined, and are expected to be useful for the design of new selective inhibitors.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Carbamoylphosphonic acids
Matrix metalloproteinase inhibitors
Metal complexes
Zinc binding groups
Megjelenés:Journal Of Biological Inorganic Chemistry. - 9 : 3 (2004), p. 307-315. -
További szerzők:Katz, Yiffat Bhusare, Sudhakar Reich, Reuven Röschenthaler, Gerd-Volker Königsmann, Martin Breuer, Eli
Pályázati támogatás:TS 040685
OTKA
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4.

001-es BibID:BIBFORM084854
035-os BibID:(cikkazonosító)P 242
Első szerző:Farkas Etelka (vegyész)
Cím:Ligand architectures as factors affecting the thermodynamic and redox stability of metal ion-siderophore complexes / Etelka Farkas, Orsolya Szabó, István Pócsi
Dátum:2014
ISSN:0949-8257
Tárgyszavak:Természettudományok Kémiai tudományok idézhető absztrakt
folyóiratcikk
Megjelenés:Journal of Biological Inorganic Chemistry. - 19 : Suppl 2 (2014), p. S861. -
További szerzők:Szabó Orsolya (vegyész) Pócsi István (1961-) (vegyész)
Pályázati támogatás:TÁMOP 4.2.2.A-11/1/KONV-2012-0043
TÁMOP
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5.

001-es BibID:BIBFORM006211
Első szerző:Müller, Holger
Cím:New pyrazole-based ligands with two tripodal binding pockets : potential scaffolds for metallobiosite modeling / Muller, H., Bauer-Siebenlist, B., Csapo, E., Dechert, S., Farkas, E., Meyer, F.
Dátum:2008
ISSN:0020-1669
Megjegyzések:The synthesis of a new set of bioinspired dinucleating ligand scaffolds HL1-HL3 based on a bridging pyrazolate with appended chelate arms is reported. The ligands provide two binding compartments akin to the tris(imidazolyl)methane motif, predisposed to act as facially tridentate coordination caps. Potentiometric titrations of HL1 in the presence of Ni2+ and Zn2+ reveal formation of species with a metal:ligand ratio 1:1 in aqueous solution, and UV-vis data for the Ni-II system suggest that the complex [(L2Ni2)-Ni-1](2+) with {NiN6} chromophore is formed under appropriate pH conditions. In contrast, trinickel(II) complexes [(L2Ni3)-Ni-2(NO3)(4)(MeOH)(2)] (4) and [(L2Ni3Cl2)-Ni-2(MeOH)(4)]Cl-2 (5) could be obtained from MeOH solutions and characterized crystallographically. The anticipated tripodal {N-3} binding mode of the ligand is indeed realized for the central Ni-II ion, but the counteranions or MeOH solvent molecules lead to dissociation of one of the N donor legs for the outer Ni-II ions with formation of intramolecular H-bonds between a Ni-bound MeOH and the pyrazolate-N. X-ray crystals structures were also obtained for three Cu-I complexes [(L2Cu4X2)-Cu-3](PF6)(2) with X = PMe3 (6), CNnBu (7), CNC6H3Me2-2,6 (8), where all Cu-I ions are three-coordinate in a distorted trigonal-planar arrangement. The two inner metals are bound to two imidazole-N from one ligand sidearm and a pyrazolate-N from the other ligand while the outer Cu-I ions are hosted by the pyrazolate-N and one imidazole-N from the nearby sidearm with the third coordination site filled by the coligand X. Spectroscopic and ESI-MS data suggest that the trinickel complexes stay intact even in coordinating solvents while the Cu-I complexes in solution are partly dissociated into their bimetallic constituents. The solid state structures observed for the oligonuclear complexes 4-8 are reminiscent of the coordination motifs previously found for related mononuclear complexes based on tripodal tris (imidazolyl)methane, which corroborates the description of HL1-HL3 as novel binucleating versions of such tris (imidazolyl) methane ligands.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Inorganic Chemistry. - 47 : 12 (2008), p. 5278-5292. -
További szerzők:Bauer-Siebenlist, Bernhard Csapó Edit (1983-) (vegyész) Dechert, Sebastian Farkas Etelka (1948-) (vegyész) Meyer, Franc
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6.

001-es BibID:BIBFORM003032
Első szerző:Prokofieva, Angelina
Cím:Oligonuclear copper complexes of a bioinspired pyrazolate-bridging ligand : synthesis, structures, and equilibria in solution / Angelina Prokofieva, Alexander I. Prikhod'ko, Eva Anna Enyedy, Etelka Farkas, Walter Maringgele, Serhiy Demeshko, Sebastian Dechert, Franc Meyer
Dátum:2007
ISSN:0020-1669
Megjegyzések:The synthesis of a new bioinspired dinucleating ligand scaffold based on a bridging pyrazolate with appended bis[2-(1-methylimidazolyl)methyl]aminomethyl chelate arms is reported. This ligand forms very stable copper complexes, and a series of different species is present in solution depending on the pH. Interconversions between these solution species are tracked and characterized spectroscopically, and X-ray crystallographic structures of three distinct complexes that correspond to the species present in solution from acidic to basic pH have been determined. Overall, this provides a comprehensive picture of the copper coordination chemistry of the new ligand system. Alterations in the protonation state are accompanied by changes in nuclearity and pyrazolate binding, which cause pronounced changes in color and magnetic properties. Antiferromagnetic coupling between the copper(II) ions is switched on or off depending on the pyrazole binding mode.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Inorganic Chemistry. - 46 : 10 (2007), p. 4298-4307. -
További szerzők:Prikhod'ko, Alexander I. Enyedy Éva Anna (1975-) (vegyész) Farkas Etelka (1948-) (vegyész) Maringgele, Walter Demeshko, Serhij Dechert, Sebastian Meyer, Franc
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7.

001-es BibID:BIBFORM003033
Első szerző:Santos, Amélia M.
Cím:Complexation of molybdenum(VI) with bis(3-hydroxy-4-pyridinone)amino acid derivatives / M. Amélia Santos, Sofia Gama, João Costa Pessoa, M. Conceição Oliveira, Imre Tóth, Etelka Farkas
Dátum:2007
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:European Journal Of Inorganic Chemistry. - 12 (2007), p. 1728-1737. -
További szerzők:Gama, Sofia Pessoa, Joăo Costa Oliveira, M. Conceição Tóth Imre (1950-) (vegyész) Farkas Etelka (1948-) (vegyész)
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8.

001-es BibID:BIBFORM095729
Első szerző:Selmeczi Katalin
Cím:Mono-versus binuclear copper(II) complexes in phosphodiester hydrolysis / Katalin Selmeczi, Michel Giorgi, Gábor Speier, Etelka Farkas, Marius Réglier
Dátum:2006
ISSN:1434-1948
Megjegyzések:Mono- and dinuclear copper(II) complexes [Cu(L1OH)]-(CF3SO3)2(1) and [Cu2(L2O)](CF3SO3)3(2) have been synthe-sized and characterized by X-ray crystallography. Complexes1 and 2 were then tested as catalysts for the hydrolysis of bis(p-nitrophenyl)phosphate (BNPP). At pH 6, the dinuclear complex 2 was found to be 20-fold more active than complex1 and the reaction up to 600-fold faster than the un-promoted reaction. On the basis of potentiometric studies, we were able to demonstrate that the bis(aqua)copper complex was the active species by the formation of a ternary complex in which one copper atom binds to a hydroxide and the second,to the substrate. We also propose that BNPP reacts with the bis(aqua)copper complex to give a stable, hydrolytically in-active BNPP-2 complex (3).
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Catalysis
Dinuclear copper(II) complex
Enzyme mimics
Phosphate ester hydrolysis
Tripodal ligands
Megjelenés:European Journal of Inorganic Chemistry. - 2006 : 5 (2006), p. 1022-1031. -
További szerzők:Giorgi, Michel Speier Gábor Farkas Etelka (1948-) (vegyész) Réglier, Marius
Pályázati támogatás:43414
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