metalloporphirins; cu(tpp), mn(tpp)cl, co(tpp), fe(tpp)cl, zn(tpp) and mn(obp)cl catalyze region and chemoselective silylation of hydroxyl groups with hmds. fe(tpp)cl is the most effective catalyst and silylation occurs immediately in its presence at room temperature.

When a number of metal ions were tested as activators over a lOO-fold range of metal ion concentration (0.01 to 1.0 mM), aconitase was specifically activated by Fe(II). Manganese(I1) does not activate aconitase but binds to the enzyme, as shown indirectly by inhibition of the enzyme activation by Fe(I1) and directly by electron paramagnetic resonance. A titration of the enzyme with Mn(I1) may b...

Ahstract--Mn-substituted iron oxides were synthesized by coprecipitating Fe(NO3)3 and Mn(SO4) solutions with NH4OH, adjusting the suspensions to pH 4 or 6, and then keeping the suspensions at 55~ for 62 days. The Mn mole fraction of the final products ranged from 0 to 0.3. X-ray powder diffraction patterns showed that goethite and hematite formed in each Fe-containing system. Groutite formed in...

We explore Fe/Mn and Nb/Ta ratios of basalts as potential tracers for differentiating melts of recycled mafic crustal lithologies from peridotitic melts. Trace elements and Fe/Mn ratios of the Mesozoic and Cenozoic basalts from East China were analyzed by ICP-MS. Low Nb/Ta ratios (15.4 ± 0.3 (2r, n = 45)), high Nb and Ta contents (60.1 and 4.01 ppm) and high Fe/ Mn ratios (64.7 ± 1.5 (2r, n = 4...

The uptake of Mn(2+), a cofactor for several enzymes in Escherichia coli, is mediated by MntH, a proton-dependent metal transporter, which also recognizes Fe(2+) with lower affinity. MntH belongs to the NRAMP family of eukaryotic Fe(2+) and Mn(2+) transporters. In E. coli strains with chromosomal mntH-lacZ fusions, mntH was partially repressed by both Mn(2+) and Fe(2+). Inactivation of fur resu...

I . The minced carcases of twenty-seven lambs, ranging from 18 to 69 kg in live weight, and twenty-five calves (30-90 kg) were analysed for copper, iron, manganese and zinc. The lambs were weaned whereas the calves were reared exclusively on milk. 2. Mean concentrations of Fe, Mn and Zn for groups of lamb carcases fell within the ranges 52.6-75.1, 0.7-1.2 and 20.8-25.6 mg/kg fresh carcase weigh...

Over the last two decades, considerable attention has been paid to the management of metal-contaminated soils. Fe-Mn concretions and nodules can be used to sequester metals by adsorption. Fe-Mn concretions and nodules are discrete bodies with variable compositions formed in the soil system under alternating oxidizing and reducing conditions. This chapter highlights the high adsorption capacity ...

The micronutrient density of seeds is important not only for human nutrition but also for the nutrition of the next generation seedling. Deficiencies of zinc (Zn), iron (Fe) and manganese (Mn) in soils and crops occur nearly in all countries, particularly in cereals growing areas. The deficiencies adversely affect both food production and human health in a major part of the world. Therefore, va...