Manganese, ion

Left side of Fig. 4 shows a ribbon model of the catalytic (C-) subunit of the mammalian cAMP-dependent protein kinase. This was the first protein kinase whose structure was determined [35]. Figure 4 includes also a ribbon model of the peptide substrate, and ATP (stick representation) with two manganese ions (CPK representation). All kinetic evidence is consistent with a preferred ordered mechanism of catalysis with ATP binding proceeding substrate binding. 

Under acidic conditions, pH < 3.5, and in the presence of certain reducing agents, the permanganate ion can undergo a five-electron exchange resulting in the divalent manganese ion. 

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). 

Oxides of manganese and iron are often found deposited together. Similar conditions cause oxidation of both iron and manganese ions. Exposure to oxygenated water, chlorination, and some microbiological processes causes such oxidation. Often, a few percent chlorine is found in deposits, possibly because of associated chlorination. 

Discussion. In mixtures of magnesium and manganese the sum of both ion concentrations may be determined by direct EDTA titration. Fluoride ion will demask magnesium selectively from its EDTA complex, and if excess of a standard solution of manganese ion is also added, the following reaction occurs at room temperature ... 

The excess of manganese ion is evaluated by back-titration with EDTA. The amount of standard manganese ion solution consumed is equivalent to the EDTA liberated by the fluoride ion, which is in turn equivalent to the magnesium in the sample. 

Mixtures of manganese, magnesium, and zinc can be similarly analysed. The first EDTA end point gives the sum of the three ions. Fluoride ion is added and the EDTA liberated from the magnesium-EDTA complex is titrated with manganese ion as detailed above. Following the second end point cyanide ion is added to displace zinc from its EDTA chelate and to form the stable cyanozincate complex [Zn(CN)4]2- the liberated EDTA (equivalent to the zinc) is titrated with standard manganese-ion solution. 

After the end point, add 2.5 g of sodium fluoride, stir (or agitate) for 1 minute. Now introduce the standard manganese (II) sulphate solution from a burette in 1 mL portions until a permanent red colour is obtained note the exact volume added. Stir for 1 minute. Titrate the excess of manganese ion with EDTA until the colour changes to pure blue. 

After the second end point, add 4-5 mL of 15 per cent aqueous potassium cyanide solution (CARE), and run in the standard manganese ion solution from a burette until the colour changes sharply from blue to red. Record the exact volume of manganese(II) sulphate solution added. 

Lithium extraction from thin-film LiMn204 electrodes takes place in several stages. It has been proposed that lithium is first extracted from the tetrahedral sites at approximately 4 V. Second, because the manganese ions in these thin-film LiMn204 electrodes appear to be... 

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

The set of all intermediate steps is called the reaction pathway. A given reaction (involving the same reactants and products) may occur by a single pathway or by several parallel pathways. In the case of invertible reactions, the pathway followed in the reverse direction (e.g., the cathodic) may or may not coincide with that of the forward direction (in this example, the anodic). For instance, the relatively simple anodic oxidation of divalent manganese ions which in acidic solutions yields tetrava-lent manganese ions Mn +— Mn -l-2e , can follow these two pathways ... 

The second pathway includes a step in which the trivalent manganese ions formed as intermediates disproportionate. 

Metal-free cotton material samples were impregnated with standard solutions of iron, copper, and manganese ions containing 10 to 100 )a,g of metal per gram of cotton material. It was completely dried and 1 g of cotton sample was combusted... 

Primary clay, for example kaolin, is colorless, and when such clay is heated to a high temperature it produces white ceramic materials. Most pottery, however, is colored its color is due to the fact that most of it was, and still is, made not from primary but from secondary clay. Secondary clay contains minerals other than clay, and colored metal ions in them endow the pottery with their color. Iron ions (in iron oxides), for example, tend to make pottery yellow, brown, or red, and manganese ions (in pyrolusite, a mineral composed of manganese oxide) make it either dark or black. 

The vanadium(IV) complex of salen in zeolite was found to be an effective catalyst for the room temperature epoxidation of cyclohexene using t-butyl hydroperoxide as oxidant.88 Well-characterized vanadyl bis-bipyridine complexes encapsulated in Y zeolite were used as oxidation catalysts.101 Ligation of manganese ions in zeolites with 1,4,7-triazacyclononanes gives rise to a binu-clear complex stabilized by the zeolites but allows oxidation with excellent selectivity (Scheme 7.4). 

Now the possible explanation for the greater degradation of phenol by the cerium doped copper crystals than those of either cobalt or manganese ions could... 

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