Mechanism polyamine complex

It was proposed that mono-protonation of [CuL]2+ to yield [Cu(HL)]2+ occurs initially at the axial nitrogen atom since this Cu-N bond is expected to be weaker as a result of Jahn-Teller distortion. With respect to this, it should be noted that species such as [Cu(HL)]3+ are commonly observed during potentiometric studies of the formation of Cu(n) polyamine complexes. From the proposed mechanism, the following rate law can be deduced ... 

The vast majority of the macrocyclic complexes of the lanthanide(III), yttrium(III) and uranyl ions obtained so far by metal-templated synthesis are of the Schiff-base type even the few known examples of simple polyamine complexes actually result from the cyclic condensation of a diamine with a (modified) carbonyl precursor. In general, the metal-templated synthesis is facilitated by the presence of oxygen-donor anions, such as nitrate, acetate, or trifluoromethylsulfonate lanthanide(III) thiocyanates have also been successfully used. With a few exceptions, the outcome of the synthesis appears to be independent of the order of addition of the reactants. No deliberate attempts have been made to investigate the detailed mechanism of these metal-templated cyclic condensation reactions. 

A more detailed understanding of the conjugate-base mechanism for the hydrolysis of kinetically inert amine complexes of cobalt(III) and rhodium(III) is possible if liquid ammonia is used as a solvent. Such techniques allow the separation of parameters for the pre-equilibrium step ( Tcb) and the rate-determining step. A polyamine complex generally contains more than one potentially acidic proton and each proton is characterized by its own acidity constant (Kcb)- exchange rates for... 

FernAndez, C. O. Hoyer, W. Zweckstetier, M. Jares-Eruman, E. a. Subramaniam, V. Griesinger, C. JovM, T. M. NMR of a-synuclein-polyamine complexes elucidates the mechanism and kinetics of induced aggregation. EMBO J. 2004, 23, 2039 2046. 

In some cases, the unidentate ligand is liberated at the end of the reaction. Usually, however, the ligand is found in both the reactant and the product. The effect has been most systematically examined for Ni(II). Coordinated NHj and polyamines have the largest accelerating influence. The rate acceleration induced by macrocycles resides primarily in reduced AFTI values (by 15-26 kJ mol ). The 6- and 5-coordination of solvated tetramethylcyclam complexes is controlled by the conformation at the 4 N-centers, 2 and 3. These complexes exchange by and 4 mechanisms, respectively, as indicated by positive and negative values (Table 4.9). Also Sec. 4.9. 

Fig. 1 Proposed mechanism of gene transfection [117]. (1) Formation of the DNA/polymer complex (polyplex), (2) endocytosis of the polyplex, (3) fusion of endosome and lysosome, (4) release of the polyplex into the cytosol, (5a) incorporation of the polyplex into the nucleus, (5b) release of the siRNA into the cytosol, (6) transcription of the DNA into mRNA followed by release of the polyamine back into the cytosol, (7a) translation of mRNA, and (7b) mRNA degradation. The metabolism of the polyamine is still unclear. Reproduced with permission from [117]. Copyright 2002 Elsevier...

A 1,10-phenanthroline-containing polyamine macrocycle (78) was designed to complex with Zn2+ ion and, because of the rigidity of the phenanthroline moiety, leave some free binding sites at the metal for ligands such as water, which easily depro-tonate to give stable hydroxo species. The hydrolysis of methyl acetate in the gas phase by such a monohydroxy-Zn(II) complex [Zn(78)(OH)]+ has been investigated by quantum mechanical procedures and some pathways delineated.78... 

Fig. 2. The possible mechanism of NEM-induced nociceptive behavior. NEM inhibits the degradation of endogenous dynorphins, presumably big ( Kuorphin. and accumulated dynorphins activate the NMDA receptor ion-channel complex by acting on the polyamine recognition site and then induce nociceptive behavior. Dyn dynorphin.

The Co(m)-complex of cyden, Co(m)Cyc, is one of the most effedive synthetic catalysts discovered so far for the hydrolysis of supercoiled DNAs [59]. The hydrolytic nature of DNA cleavage by the Co(m) complexes of polyamines including cyden has been well documented [57, 58]. The mechanism illustrated in 25 has been proposed [57] for the catalytic action of the Co(m) complexes. Given the remarkable enhancement of proteolytic activity of Cu(n)Cyc upon attachment to PCD [49], we tested the activity of Co(m)Cyc in phosphodiester hydrolysis to see if it is also enhanced greatly upon attachment to PCD derivatives [61, 62]. 

As for deaminase, the kinetic analysis suggests a partial mixed-type inhibition mechanism. Both the Ki value of the inhibitor and the breakdown rate of the enzyme-substrate-inhibitor complex are dependent on the chain length of the PolyP, thus suggesting that the breakdown rate of the enzyme-substrate-inhibitor complex is regulated by the binding of Polyphosphate to a specific inhibitory site (Yoshino and Murakami, 1988). More complicated interactions were observed between PolyP and two oxidases, i.e. spermidine oxidase of soybeen seedling and bovine serum amine oxidase. PolyP competitively inhibits the activities of both enzymes, but may serve as an regulator because the amino oxydases are also active with the polyamine-PolyP complexes (Di Paolo et al., 1995). 

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