Manganese activation

Some oxide-type minerals have been found to luminesce when irradiated. A simple example is ruby (aluminium oxide with chromium activator), which emits bright-red light. The phosphors are incorporated into colour television screens to emit the colours blue (silver-activated zinc sulphide), green (manganese-activated zinc orthosilicate), and red (europium-activated yttrium vanadate). 

This two-point measurement technique is used in the system reported by Wicker-sheim and Sun,(27) where a lamp phosphor, tetravalent manganese-activated magnesium fluorogermanate, mentioned above, is used as fluorescent sensor. The excitation... 

Another example is the balanced integration method described by Sun.(29) This technique is designed to achieve 0.01°C resolution using tetravalent manganese-activated magnesium fluorogermanate, the same sensor material that has been used... 

The coatings of many TLC plates contain a manganese-activated zinc silicate that glows bright green under fluorescent light (254 nm). Samples that absorb UV light at that wave-... 

Photoluminescent sulfates are obtained by activation with ions that absorb short-wavelength radiation, for example, Ce3 +. Alkali-metal and alkaline-earth sulfates with Ce3 + emit between 300 and 400 nm. On additional manganese activation, the energy absorbed by Ce3 + is transferred to manganese with a shift of the emission into the green-to-red region. 

Other Halide Phosphors. Information on the most important manganese-activated phosphors is summarized in Table 57. 

Manganese acts as a cofactor of mevalonate kinase and farnesyl pyrophosphate synthetase. Mevalonate kinase and possibly one other manganese-activated enzyme are necessary for the formation of mevalonate from acetate (3). Farnesyl pyrophosphate synthetase acts to add one 5-carbon unit to geranyl pyrophosphate to make farnesyl pyrophosphate (4) (Figure 1). 

Manganese-activated enzyme an enzyme that does not bind Mn tightly, but for which the enzymatic activity is nevertheless enhanced by addition of Mn. Manganese may or may not be the cation bound in vivo... 

In contrast to manganese-activated enzymes, manganoen-zymes contain tightly bound Mn and it is often quite difficult to remove the Mn from the protein. The activity of manga-noenzymes is not enhanced by the addition of free Mn to the assay medium. Both classes of proteins are discussed since the distinction involves only the relative strength of the Mn-protein interaction and not any fundamental properties of the Mn active site. 

Many other metal ions have been reported as catalysts for oxidations of paraffins or intermediates. Some of the more frequently mentioned ones include cerium, vanadium, molybdenum, nickel, titanium, and ruthenium [21, 77, 105, 106]. These are employed singly or in various combinations, including combinations with cobalt and/or manganese. Activators such as aldehydes or ketones are frequently used. The oxo forms of vanadium and molybdenum may very well have the heterolytic oxidation capability to catalyze the conversion of alcohols or hydroperoxides to carbonyl compounds (see the discussion of chromium, above). There is reported evidence that Ce can oxidize carbonyl compounds via an enol mechanism [107] (see discussion of manganese, above). Although little is reported about the effectiveness of these other catalysts for oxidation of paraffins to acetic acid, tests conducted by Hoechst Celanese have indicated that cerium salts are usable catalysts in liquid-phase oxidation of butane [108]. 

Experiments done on isolated chloroplasts showed that all the chloroplast reactions tested are inhibited by copper and that manganese reduced this effect96. The lack of influence of light in these experiments implies that the photoact per se is not involved. The authors suggested that a manganese activated enzyme was involved. Another possible mechanism is that copper and manganese both influence membrane permeability, but in opposite directions. 

The TLD consists of inorganic crystals of lithium fluoride (LiF) or manganese-activated calcium fluoride (CaF2 Mn) held in holders and is commonly used for finger exposures. TLDs exposed to radiations emit light when heated at 300-400° C and the amount of light emitted is proportional to... 

Manganese-activated zinc silicate, zinc/cadmium sulfide, lead/manganese-activated calcium silicate. 

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