Metal ions oligomers

Imidazolides of adenylic acid (ImpA) or uridylic acid (ImpU) are polycondensed to oligonucleotides by means of Zn2+ ions. 1673 The resulting phosphordiester bond was found to be of the 2, 5 type. In the reaction of nucleoside 5 -phosphoric acid methyl ester with ImpA in the presence of MgC, 2, 5 -dinucleotides are formed six to nine times more frequently than the corresponding 3, 5 compounds. 63 Polycondensations of ImpA in aqueous solution in the presence of various divalent metal ions lead to short oligo-adenylic acids (pA) (n = 1—5) mainly with 2, 5 -intemucleotide linkages. With Pb2+, for example, the total yield of oligomers was as high as 57%. 1683 1693... 

In the absence of any added salts, the distribution of adducts formed was found to be variable by ESI—MS. In general, however, the lower molecular weight surfactant oligomers showed a preference for the Na+ adduct, whilst the higher oligomers showed an increase in preference for the K+ adduct. This is consistent with the metal-ion complexing abilities described for polyether derivatives [39,40], Simplification of the spectra was achieved with the addition of salt solutions to the mobile phase, as shown for NH4C1 in Fig. 2.8.4 [29], With the addition of salt... 

MALDI is the method of choice for the analysis of synthetic polymers because it usually provides solely intact and singly charged [62] quasimolecular ions over an essentially unlimited mass range. [22,23] While polar polymers such as poly(methylmethacrylate) (PMMA), [83,120] polyethylene glycol (PEG), [120,121] and others [79,122,123] readily form [M+H] or [M+alkali] ions, nonpolar polymers like polystyrene (PS) [99,100,105,106] or non-functionalized polymers like polyethylene (PE) [102,103] can only be cationized by transition metal ions in their l-t oxidation state. [99,100] The formation of evenly spaced oligomer ion series can also be employed to establish an internal mass calibration of a spectrum. [122]... 

A number of rate constants for reactions of transients derived from the reduction of metal ions and metal complexes were determined by pulse radiolysis [58]. Because of the shortlived character of atoms and oligomers, the determination of their redox potential is possible only by kinetic methods using pulse radiolysis. In the couple Mj/M , the reducing properties of M as electron donor as well as oxidizing properties of as electron acceptor are deduced from the occurrence of an electron transfer reaction with a reference reactant of known potential. These reactions obviously occur in competition with the cascade of coalescence processes. The unknown potential °(M /M ) is derived by comparing the action of several reference systems of different potentials. 

Copolymers of methacrylic add and ethylene termed as ethylene ionomers have been used as the base polymer for binding alkali, alkaline earth and transition metal ions. Organic amines such as n-hexylamine, hexamethylene tetraamine, 2,2,6,6-tetramethyM-hydroxy piperazine, ethylene diamine and polymeric diamines such as silicone diamine, polyether diamine and polymeric diamines such as silicone diamine, polyether diamine and polyamide oligomers considerably enhance the complex formation characteristics of Zn(II) ethylene ionomers thereby enhancing the physico-chemical properties [13]. 

A variety of chromium(III) and cobalt(III) oligomers can be prepared by oxidation of an aqueous solution of the appropriate divalent metal-ion complex with oxidants such as 02 and Tl3 +. The... 

Structural, thermodynamic, and kinetic studies have shown that hydroxo-bridged polynuclear complexes of (diromium(III), cobalt(III), rhodium(III), and iridium(III) have many general features in common. Structurally, the four metal ions exhibit an almost identical pattern, and in particular the occurrence of many well-characterized oligomers... 

This property of organic ligands (peptides, in particular) and their oligomers, coordinated with metal ions, opens up good possibilities for the development of highly active catalytic systems. Hence, such systems can be well soluble in water and operate at biologically suitable pH. 

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