Because of the complexity of molybdate solutions often used for catalyst preparation, studies have been carried out to ascertain their solution properties and adsorption behavior as a function of pH, concentration, time, temperature, and the presence of oxalate ligands. It has been shown that the solubility and solution stability of ammonium isopolymolybdates vary as a function of the concentration of molybdenum, the pH of solution, and the NH3/M0O3 molar ratio of the solution. The presence of hydrogen peroxide markedly increases both the solution stability and solubility of the isopolymolybdate anions. Extensive adsorption studies of such solutions onto -203 and silica-aluminas were carried out employing ( 4)2 207, ( 4)ß 7024•4 20 along with their peroxy species, and H2[Mo03C204]•2 20 and its two ammonium salts. The adsorption behavior of these anionic species Is dependent upon the nature and concentration of the complex and upon the time of contact. Spectral characterization has been used to elucidate the interactions occurring in the supported species in the solvated and dried forms.
Estrogen receptor alpha (ERalpha) serine 118 (Ser118) phosphorylation modulates activation function-1 (AF1) function. Correct positioning of helix 12 promotes agonist-dependent recruitment of cyclin-dependent kinase-7 to catalyze this event. In this study we show robust cyclin-dependent kinase-7-independent, AF2 antagonist-induced Ser118 phosphorylation. Estradiol (E2) and ICI-182,780 (ICI-780) induce Ser118 phosphorylation of wild-type ERalpha and either of two helix 12 mutants, suggesting AF2-independent action, probably via shedding of 90-kDa heat shock protein. With E2 treatment, the predominantly nuclear, phosphorylated ERalpha in COS-1 cells is detergent soluble. Although levels of ICI-780-induced phosphorylation are profound, Ser118-phosphorylated ERalpha is aggregated over the nucleus or in the cytoplasm, fractionating with the cell debris and making detection in cleared lysates improbable. Selective ER modulators (SERMs) elicit a mixed response with phosphorylated ERalpha in both detergent-soluble and -insoluble compartments. Apparent ligand-induced loss of ERalpha protein from cleared lysates is thus due to ligand-induced redistribution into the pellet, not degradation. The COS-1 response to ICI-780 can be mimicked in MCF-7 cells treated with a proteasome inhibitor to block authentic ligand-induced degradation. With SERMs and antagonists, the magnitude of Ser118-phosphorylated receptor redistribution into the insoluble fraction of COS-1 cells correlates with the magnitude of authentic ERalpha degradation in MCF-7 cells. A strong inverse correlation with ligand-induced uterotropism in vivo (P < 0.0001) and direct correlation with AF2-independent transrepression of the matrix metalloprotease-1 promoter in endometrial cells in vitro are seen. These data suggest that ligand-induced Ser118 phosphorylation of ERalpha can be AF2 independent. Furthermore, they identify translocation of Ser118-phosphorylated ERalpha out of the nucleus, leading to cytoplasmic aggregation, as an antagonist pathway that may precede receptor degradation.
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