Manganese ions activation

Metal-Catalyzed Oxidation. Trace quantities of transition metal ions catalyze the decomposition of hydroperoxides to radical species and greatiy accelerate the rate of oxidation. Most effective are those metal ions that undergo one-electron transfer reactions, eg, copper, iron, cobalt, and manganese ions (9). The metal catalyst is an active hydroperoxide decomposer in both its higher and its lower oxidation states. In the overall reaction, two molecules of hydroperoxide decompose to peroxy and alkoxy radicals (eq. 5). 

Manganese ions enzyme activators, 6,578 probes, 6,563 RNA polymerases activation, 6, 585 transport microbes, 6, 569 plants, 6, 572 Manganese oxide colloidal... 

Fig. 9. Logarithm of the cation activity coefficient versus the square root of the concentration for the system of manganese ions and cation vacancies in sodium chloride at 500°C. Filled-in circles represent the association theory with Rq = 2a, and open circles the association theory with R = 6/2. Crosses represent the present theory with cycle diagrams plus diagrams of two vertices, and triangles represent the same but with triangle diagram contributions added.

Mounter and his co-workers3 designate this enzyme responsible for the hydrolysis of D.F.P. as dialkylfluorophosphatase (D.F.P.-ase). They have shown that D.F.P.-ase from hog kidney is activated by cobalt and manganese ions. In the presence of... 

Nonradiative energy transfer is very often used in practical applications, such as to enhance the efficiency of phosphors and lasers. A nice example is the commercial phosphor Cas(P04)3 (FCl), which is doubly activated by Sb + and Mn + ions. When the phosphor is singly activated by Mn + ions, it turns out to be very inefficient, due to the weak absorption bands of the divalent manganese ion. However, coactivation with Sb + ions produces a very intense emission from the Mn + ions, because the Sb + ions (the donor centers) efficiently absorb the ultraviolet emission (253.6 nm) of... 

The enzyme that catalyzes reaction 7 has been solubilized, 4" 141 and purified141 2000-fold. The enzyme activity is dependent on manganese ions. The enzymes catalyzing reactions 5 and 6 have not yet heen solubilized, purified, or separated, and, therefore, the substrate specificities indicated remain speculative. 

An ATP-dependent DNase has been partially purified from extracts of E. coli by Oishi (86) and Barbour and Clark (37). It shows an absolute requirement for magnesium or manganese ion and has a broad pH optimum ranging from pH 7.5 to 9.5. The partially purified enzyme preferentially degrades native DNA (including glucosylated T4 DNA) and has an almost absolute requirement for ATP or dATP. Current preparations of the enzyme are also active on denatured DNA however, there is only a slight stimulation of hydrolysis by added ATP. This latter activity may therefore represent some contamination with exonuclease I. The mode of attack is stated to be exonucleolytic. 

Not surprisingly, both manganese ions are necessary for the catalase activity of arginase, as confirmed by metal replacement experiments in a mutant arginase. Indeed, whereas the hydrolytic reaction was restored upon binding one Cd2+ ion to form a heteronuclear MnCd enzyme, catalase activity was not [111]. 

The enzyme responsible for the photolysis of water in plants is a multisubunit membrane protein (Fig. 5-22 Klein et al., 1991). Four manganese ions, probably as a tetranuclear cluster, are thought to act as a charge accumulating system and as the active site for water oxidation. Both calcium and chloride ions are also required for activity (Babcock, 1987 Ghantokakis and Yocum, 1990). The water oxidation centre (WOC) contains a total of four Mn atoms and causes the oxidative coupling of two water molecules by a currently unknown mechanism. 

Manganese ions, Mn2+ Present in some enzymes, it activates blood haemoglobin synthesis, urea formation, growth, reproduction processes and release of insulin. Manganese ions also take part in enzyme control in the brain Zinc ions, Zn2+ Small quantities help carbon dioxide metabolism and removal. Zinc is... 

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