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Wyszukujesz frazę "Metal complexes" wg kryterium: Temat


Wyświetlanie 1-4 z 4
Tytuł:
Peptydy jako potencjalne ligandy wiążące jony metali przejściowych
Peptides as potential ligands binding transition metal ions
Autorzy:
Krupa, K.
Lesiów, M. K.
Kowalik-Jankowska, T.
Powiązania:
https://bibliotekanauki.pl/articles/171519.pdf
Data publikacji:
2018
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
peptydy
reszta histydylowa
kompleksy metali
model koordynacyjny
peptides
histidine residue
metal complexes
coordination mode
Opis:
Peptides are crucial ligands for transition metal ions and form complexes with them, that can have important biological activity. Many factors impact on the creation of complexes such as: protection of amine group from N-terminal or carboxylate group from C-terminals of the protein, the presence of noncoordinating and coordinating side chains in the peptide sequence, the number of histidyl residues and their location in the peptide chain. In complexes the metal ion can be bound bound by various donor atoms from amino acids residues (e.g. nitrogen, oxygen or sulphur). In general, the protection of N- or C-terminal groups influences the less stable formation of complexes. Stable complexes are created, if the free amine group from the N-terminal is involved in the coordination process. Peptides with noncoordinating side chains include alanine or glycine. Glycine complexes are more stable than these with alanine. Histidyl residue is the most effective amino acid residue in binding metal ions. The amine group of the lysyl residue, thiol from cysteine or carboxylate from aspartyl or glutamyl residues are also functional groups that coordinate metal ions. The coordination process is initiated by a group that anchors metal ion. A free amine group from N-terminus or imidazole nitrogen are the best examples of anchor groups. The metal ions can also be bound through amide nitrogens, after their forced deprotonation by the anchor group and formation of chelate rings. Peptides containing two or more histidyl residues exhibit high structural diversity in the complexes formation. In addition, these peptides can also form macrochelates and polynuclear complexes. The location of amino acid residues in the peptide chain (especially histydyl residue) also results in the thermodynamically stable formation of complexes.
Źródło:
Wiadomości Chemiczne; 2018, 72, 7-8; 597-608
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Antybiotyki peptydowe i ich kompleksy z jonami metali
Peptide antibiotics and their complexes with metal ions
Autorzy:
Stokowa-Sołtys, K.
Powiązania:
https://bibliotekanauki.pl/articles/171960.pdf
Data publikacji:
2018
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
antybiotyki peptydowe
metaloantybiotyki
kompleksy jonów metali
peptide antibiotics
metalloantibiotic
metal ion complexes
Opis:
Metal ions are essential for numerous antibiotics. They play a crucial role in the mechanism of action and may be involved in specific interactions with cell membrane or target molecules, such as: proteins and nucleic acids. Due to the fact that complexes usually poses a higher positive charge than free ligands, they might interact more tightly with DNA and RNA molecules. However, complexes may also form during antimicrobial agents application, because a lot of them possess functional groups which can bind metal ions present in physiological fluids. Many recent studies support a hypothesis that drugs may alter the serum metal ions concentration. Moreover, it has been shown that numerous complexes with antibiotics can cause DNA degradation, e.g. bleomycin which form stable complexes with redox metal ions and split the nucleic acids chain via the free radicals mechanism. Therefore, it is widely used in cancer therapy.
Źródło:
Wiadomości Chemiczne; 2018, 72, 7-8; 497-522
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ditlenek węgla w syntezie organicznej
Carbon dioxide in organic synthesis
Autorzy:
Burczyk, B.
Powiązania:
https://bibliotekanauki.pl/articles/172758.pdf
Data publikacji:
2013
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
wiązanie ditlenku węgla
surowce odnawialne
synteza organiczna
kataliza
kompleksy metali przejściowych
carbon dioxide fixation
renewable resources
organic synthesis
catalysis
transition metal complexes
Opis:
Carbon dioxide is an abundant, cheap, almost nontoxic, thermodynamically stable, inert electrophile. Exploitation of CO 2 as a chemical feedstock, although will almost certainly not reduce its atmospheric concentration significantly, aims to generate high-value products and more-efficient processes. In recent years efficient transition-metal complexes have been used to perform homogeneously catalyzed transformations of CO 2 . This paper presents an overview of available catalytic routes for the synthesis of carboxylic acids, lactones, urea and carbamates, linear and cyclic carbonates as well as polycarbonates. Reduction processes of CO 2 are shortly men - tioned as well. C arboxylic acids have been synthesized via : (i) carboxylation of organolithium, organomagnesium (Scheme 2 [35]), organoboron (Scheme 3 [40 -42]), organozinc (Scheme 4 [43, 44]) and organotin (Scheme 5 [45, 46]) compounds; (ii) oxidative cycloaddition of CO 2 to olefins and alkynes (Scheme 6 -10 [47 -50, 57]) catalyzed by Ni(0)-complexes; (iii) transition-metal catalyzed reductive hydrocarboxylation of unsaturated compounds (Scheme 11, 12 [64 -67]); (iv) carboxylation of C-H bond (Scheme 13 [69 -71]). Telomerization of dienes, for instance 1,3-butadiene, and CO 2 in the presence of Ni(II) and Pd(II) complexes leads to lactones and esters of carboxylic acids (Scheme 14, 15 [73 -79]). Nucleophilic ammonia, primary and secondary amines react with CO 2 to give, respectively, urea and carbamic acid esters - carbamates and isocyanates (Scheme 16 -18 [94, 95]), thus eliminating the use of phosgene in their synthesis. CO 2 reacts with alcohols, diols and epoxides in the presence of transition-metal complexes (Fig. 2) and the reaction products are: linear carbonates (Scheme 20, 21 [110 -118]), cyclic carbonates (Scheme 22 -24 [153 -170]) and polycarbonates (Scheme 25, 26, Fig. 3, Tab. 1 [179 -186]). Finally, hydrogenation of CO 2 , leading to the formation of CO, HCOOH, CH 3 OH, CH 4 , C 2 H 6 and C 2 H 4 (Scheme 27), as well as electrochemical and photochemical reductions in the pre - sence of homogeneous and heterogeneous catalysts have been shortly reviewed.
Źródło:
Wiadomości Chemiczne; 2013, 67, 1-2; 1-53
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kompleksy jonów metali d- i f-elektronowych z N-tlenkiem pirydyny i związkami pochodnymi : badania spektroskopowe
Complexes of d- and f-metal ions with pyridine N-oxide and its derivatives: spectroscopic studies
Autorzy:
Hnatejko, Z.
Powiązania:
https://bibliotekanauki.pl/articles/171812.pdf
Data publikacji:
2011
Wydawca:
Polskie Towarzystwo Chemiczne
Tematy:
kompleksy jonów metali
jony metali
N-tlenki pirydyny
spektroskopia
complexes
metal ions
pyridine N-oxides
spectroscopy
Opis:
This article reviews results of studies, collected in the literature, related to complexation abilities of pyridine N-oxides, including forms and properties of dand f-metal ion complexes with this group of ligands. In this paper the synthetic pathways of the ligands, based on an oxidation of the corresponding heterocyclic compounds are presented (Scheme 3) [2, 4, 5]. Substituted pyridine N-oxides form an interesting group of compounds, which have found numerous applications [296-299, 314-318]. They have been used in catalysis, crystal engineering, synthesis of coordination polymers, as well as drugs and components in pharmaceutical chemistry [300-309]. Some of them are useful in destroying of microorganisms and the HIV virus [277, 278, 303-307]. Moreover, they are important compounds in the thermal and photochemical oxidation processes [296-299]. The complexes of metal ions with the N-oxide ligands can be formed by binding an oxygen atom of the N›O group, and/or by binding the substituents present in the aromatic ring, e.g. oxygen atoms of carboxylic groups. The complexes can be obtained in monomeric [64, 159], dimeric [58] or polymeric forms [60, 153, 175]. The formation of polymeric forms is more effective when the distance between the positions of COOH and N›O groups in the aromatic ring increases [168]. Complexes of Ln3+ ions and particularly of Eu3+ with pyridine N-oxides are good luminescent materials, better than their heterocyclic counterparts [180, 211]. The emission intensity of europium ions in these systems depends on the efficiency of the LMCT (ligand-metal charge transfer) and LMET (ligand-metal energy transfer) transitions, as well as on electron-donor properties of the substituents present in the pyridine N-oxide ring [37, 132, 155]. A special role in the complexation of Ln3+ ions plays cryptands, which can encapsulate the metal ion. This process protects the metal ion from a penetration of its first coordination sphere by solvent molecules or counterions [245, 246]. The complexes of europium(III) with macromonocyclic, macrobicyclic and acyclic ligands, equipped with photoactive units such as pyridine N-oxide, 2,2'-bipyridine-N,N'-dioxide or 3,3'-biisoquinoline-2,2'-dioxide in solutions, solid states, and incorporated in a silicate matrices by sol-gel method, gained a lot of attention [247-274].
Źródło:
Wiadomości Chemiczne; 2011, 65, 5-6; 461-501
0043-5104
2300-0295
Pojawia się w:
Wiadomości Chemiczne
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-4 z 4

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