Wyniki wyszukiwania - BazTech

1

Rola jonów metali w biologicznym usuwaniu fosforu ze ścieków

Mańczak M., Rucka K., Balbierz M., Balbierz P.

Wodociągi - Kanalizacja

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2009

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nr 10

32-35

2

Charakterystyka równowag kompleksowania kwasów iminodi(metylenofosfonowych) z jonami metali(II)

Kamecka A., Kurzak B.

Wiadomości Chemiczne

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2002

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[Z] 56, 3-4

315-339

EN

The aminopolyphosphonic acids are analogues of aminopolycarboxylic acids in which the carboxyl groups (CO2-) are substituted by the phosphonate moieties (PO32-). Aminopolyphosphonic acids and their derivatives have received considerable attention because of their interesting biological activity and a wide range of uses for industrial, chemical, agricultural and pharmacological purposes. This review discusses coordination preferences of N-substituted iminodi(methylenephosphonic) acids to the divalent metal ions (such as magnesium, calcium, manganese, cobalt, nickel, copper and zinc) in an aqueous solution. N-substituted derivatives of iminodi(methylenephosphonic) acids exhibit high complexation efficiency towards divalent metal ions. This results from both dinegatively charged phosphonate groups as well as the imino nitrogen present in their structure. A significant preference for an equimolar stoichiometry has been demonstrated in these systems. The only exeption is the N-2-methyltetrahydrofuryliminodi(methylenephosphonic) acid with a tetrahydrofuryl moiety placed in the sterically favoured position that allows its oxygen atom to be an effective metal binding site. Specific interactions between metal ions and furyl oxygen results in higher binding ability of this ligand and a formation of 1:2 species. The first part of the review deals with the acid-base properties of the considered ligands which are consistent with electronic effect of the substituents attached to the imino nitrogen. The second part of the review describes the binding properties of iminodi(methylenephosphonic) acids in copper(II) complexes. A formation of tridentate bonded species has been demonstrated in these systems. The third part of the review report what is known about magnesium(II), calcium(II) and zinc(II) complexes of the same ligands. While the imino nitrogen is bonded in the predominate complexes in the zinc(II) systems, magnesium(II) and calcium(II) ions prefer a pure phosphonate coordination. Finally, the interactions of manganese(II), cobalt(II) and nickel(II) ions with N-substituted iminodi(methylenephosphonic) acids are described. For these complexes the formation of eight-membered rings is reported. Coordination properties of iminodi(methylenephosphonic) acids are important factors to understand the role of the ligands and metal ions in biological systems.

3

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

Łomozik L., Gąsowska A.

Wiadomości Chemiczne

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2000

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[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.

4

Samoorganizacja w kompleksach metali

Radecka-Paryzek Wanda

Wiadomości Chemiczne

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1999

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[Z] 53, 11-12

871-885

EN

Inorganic self-organisation involves the spontaneous generation of well-defined supramolecular architectures from metal ions and organic ligands. The basic concept of supramolecular chemistry is a molecular recognition. When the substrate are metal ions, recognition is expressed in the stability and selectivity of metal ion complexation by organic ligands and depends on the geometry of the ligand and on their binding sites that it contains. The combination of the geometric features of the ligand units and of the coordination geometries of the metal ions provides very efficient tool for the synthesis of novel, intriguing and highly sophisticated species such as catenanes, box structures, double and triple helicates with a variety of interesting properties. The article will focus on the examples of inorganic self-organisation involving the templating as a first step for the assembly of supramolecular structures of high complexity.