Wyniki wyszukiwania - Biblioteka Nauki

1

Evaluation of reliability of computer analysis of potentiometric data in studies of complex-formation equlibria

100%

Łomozik L.

Chemia Analityczna

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1999

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tom Vol. 44, No. 1

89-95

EN

The process ot computer retinement ot potentiometric titration data in the complex equilibria studies was analysed in order to assess the reliability ot results. It has been shown that with a correct procedure ot model selection and proper veritication ot hypotheses, the probability ot getting a statistically good model is high. The potential drawbacks resulting trom the use ot computer techniques have been identitied and the way ot overcoming them to avoid talse results has been shown.

PL

Analizowano proces komputerowego udokładniania danych miareczkowania poten-cjometrycznego w badaniach równowag kompleksowania dla oceny wiarygodności uzyskanych rezultatów. Wykazano, że przy prawidłowej procedurze wyboru modeli i właściwej werytikacji hipotez, prawdopodobieństwo uzyskania statystycznie dobrego modelu jest wysokie. Wskazano potencjalne niebezpieczeństwa związane z zastosowa-niem technik komputerowych i sposób ich pokonania celem uniknięcia otrzymania wyników tałszywych

2

Complexes of cadmium(II) and mercury(II) with polyamines, nucleosides and nucleotides

63%

Łomozik L. , Brieger-Jarzębowska R.

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1999

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tom vol. 73 nr 6

927-940

EN

Computer analysis of potentiometric titration data was applied for determination of stability constants of Cd(II) and Hg(II) complexes in binary systems with polyamines (PA), nucleosides (Nuc) and nucleotides (NMP). For the systems of Hg(II) and PA an untypical increase in the complex stability with increasing ring size was observed and interpreted as the mercury preference to formation of linear complexes. Results of the potentiometric and 13CNMR studies for the complexes of both metal indicate the involvement of all donor nitrogen atoms of di- and triamines in the coordination, leading to formation of N2 and N3 type chromophores, respectively. Monodentate complexes of Hg(II) with Cyd are formed already at very low pH (complexes with Cd from pH of about 4). In the systems with AMP apart from nitrogen donor atoms, also the phosphate groups are involved in coordination. In the solid complexes of Cd(II) and Hg(II) with PA all donor atoms from the polyamines were found to be involved in the coordination and the presence of nitrate ions was established both in the inner and in the outer coordination spheres.

3

Complexes of Cadmium (II) and Mercury(II) with Cytidine 5'-Monophosphate and Diamines in Ternary Systems

63%

Łomozik L. , Bregier-Jarzębowska R.

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2004

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tom Vol. 78 / nr 4

529-538

EN

Formation of Cd(II) and Hg(II) complexes in ternary systems with cytidine 5_-monophosphate (CMP) and diamines (en, tn, Put) has been studied. In Hg(II)/CMP/diamine systems the formation of heteroligand compounds is accompanied by the occurrence of non-covalent interactions and the formation of molecular complexes. The presence of polyamine in ternary systems does not change the metal-nucleotide mode of coordination. Similarly as in the binary Hg(II)/CMP system, the metallation involves the donor endocyclic nitrogen N(3) atom and CMP phosphate group. On the other hand, in the Cd(II)/CMP system, the introduction of a polyamine changes the coordination mode of the nucleotide. Phosphate group, inactive in binary systems, takes part in the complexation in ternary systems. In systems of cadmium(II) ions, CMP and diamines, only molecular complexes are formed, in which the polyamine is in the outer coordination sphere. In contrast to Cd(CMP)(H2tn) and Cd(CMP)(H2Put) compounds, in Cd(CMP)(H2en) species the phosphate group of nucleotide does not take part in the metallation, i.e. the metal ion coordinates with CMP, through the atom N(3) of the nucleotide, and the phosphate group is involved in non-covalent interactions with en.

4

Jony metali jako czynnik ingerujący w oddziaływaniach poliamin z fragmentami kwasów nukleinowych

63%

Łomozik L. , Gąsowska A.

Wiadomości Chemiczne

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2000

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tom [Z] 54, 1-2

87--103

EN

Structurally simple aliphatic polyamines: putrescine (Put), spermidine (Spd) and spermine (Spm) occur in the cells of living organisms (human, animals, plants and bacteria) in relatively high concentrations. These compounds participate in many living processes [1-4 and references therein]. High basicity of polyamines implies that in the physiological conditions they appear in the protonated form and thus can interact with the negative fragments of other biomolecules. According to the polyelectrolytic theory of Manning, structural changes of particular molecules in interactions with the other components of the system depend mainly on the charge of the reagents, however, this approach does not explain a high specificity of certain reactions. It has been recently suggested that apart from the charge, also the polycation structure seems to play an important role. Computer analysis of the potentiometric titration data allowed a determination of the stability constants of molecular complexes formed by polyamines and fragments of the nucleic acids. Analysis of the titration and the spectral data indicates that at least two active centers are needed to obtain a relatively stable adduct. The thesis saying that the main sites of interactions are the protonated amine groups from PA and the negative or high electron density fragments of nucleosides or nucleotides (ion-dipole or ion-ion interactions) has been confirmed by the pH ranges of the molecular complexes occurrence. In nucleosides and nucleotides the main sites of metallation are the donor endocyclic N(3) atoms from the pyrimidine ring and N(1) or N(7) atoms from the purine ring. Phosphate groups of nucleotides are also effective centers of reaction. Polyamines change the character of the coordination dichotomy (mixture of isomers with the N(1) or N(7) coordination) observed in the metal-nucleoside (or nucleotide) systems. In general, with increasing length of the polyamine, the tendency to formation of heteroligand mixed complexes decreases and, interestingly, this tendency is exactly the opposite to that of formation of molecular complexes Nuc/PA. Already small changes in the polyamine length significantly affect their complex formation properties and reactions with metal ions or molecules in living cells. This explains the differences in the properties of biogenic amines and their biologically inactive homologues. In the ternary systems Cu/Nuc/Spm and Cu/NMP/Spm some interesting differences were observed in the coordination mode of the complexes. In the complex Cu(Nuc)(Spm) the metal ion was found to coordinate four nitrogen atoms from the polyamine in the equatorial plane and the N(3) or N(7) atom at the axial position (coordination structure of the square pyramid). In the system with the nucleotide, Cu(II) binds the phosphate group, while the polyamine is involved in non-covalent interaction with the donor nitrogen atoms from the purine or pyrimidine base and forms an adduct with intermolecular non-covalent complex-ligand interactions. In the systems with nucleosides, copper ions inhibit the interactions of adenosine or cytidine with polyamines. On the other hand, spermine involved in the non-covalent interaction with a nucleotide base blocks the potential metallation sites of AMP or CMP, changing essentially the character of coordination. Considering the role of the complexation processes in the above model systems, it should be added that formation of PA complexes with metal ions and fragments of nucleic acids is a factor ensuring homeostasis of polyamines in living cells. Reduction of the effect of diamine oxidase on the amines involved in the complexation processes increases their lifetime in living organisms.

5

Solution structure of Cu(II) complexes with spermine and nucleosides or nucleotides in ternary systems

51%

Gąsowska A. , Łomozik L. , Brieger-Jarzębowska R.

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1999

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tom vol. 73 nr 6

909-913

EN

The mode of coordination of the complexes formed in the systems Cu/spermine/nucleoside (or nucleotide) was proposed on the basis of the equilibrium and spectral studies. Significant differences were found in the coordination character of nucleosides and nucleotides. In the systems with adenosine or cytidine, mixed-ligand complexes are formed with the N5 type coordination. On the other hand, in the systems with their monophosphates, molecular complexes are formed with metal ions coordinated through monophosphates, molecular complexes are formed with metal ions coordinated through oxygen atoms from the phosphate groups. Spermine, left outside the inner coordination sphere, is involved in non-covalent interactions with nitrogen atoms from the nucleotide bases.

6

Interaction Centers of Purine and Pyrimidine Nucleotides in Their Reactions with Cu(II), Ni(II), Co(II), Cd(II) and Hg(II) Ions

51%

Gąsowska A. , Bregier-Jarzębowska R. , Łomozik L.

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2002

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tom Vol. 76 / nr 6

773-783

EN

It has been established that in ATP complexes with Cu(II), Co(II) and Cd(II) ions, the metallation centres are the oxygen atoms of the phosphate group and the nitrogen atom N(7) from the purine ring. The spectral data suggest some involvement of N(1) atom in these interactions. In the ATP complexes with Ni(II) the main centres of coordination were found to be N(7) and N(1), while the contribution of the oxygen atoms from the phosphate group is of secondary importance. In the ATP complexes with Hg(II) ions, above pH 7, the metallation involves only the oxygen atoms from the phosphate group, while the N(1) and N(7) atoms are outside the inner sphere of coordination. In the complexes of CTP with the metal ions studied the interaction centres are the oxygen atoms from the phosphate group and N(3) from the pyrimidine ring. However, in the case of complexes with Ni(II), the main centre of interaction is N(3), while the involvement of the oxygen atoms from the phosphate group is of minor importance.

7

Complexes of Copper(II) with 1,2-Diaminopropane and 2-Methyl-1,2-diaminopropane

51%

Łomozik L. , Krzyśko G. , Gąsowska A. , Bregier-Jarzębowska R.

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2008

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tom Vol. 82, nr 11

2221-2225