The high quantum efficiency of photosynthetic charge separation depends on favorable electron-transfer rates between electron donors and acceptors that are positioned in precise spatial relationships relative to one another and that possess redox potentials which result in movement of an electron down a stepped potential gradient. We have recently measured the dependence of photoinduced electron-transfer rates and subsequent dark charge recombination rates on the free energy of reaction in restricted distance porphyrin donor-quinone acceptor molecules.1 Using this information we have now synthesized a molecule for which the donor-acceptor electron-transfer rates are designed to promote efficient two-step charge separation over a known long distance. In addition to a primary porphyrin-quinone donor-acceptor pair, this molecule possesses a secondary 7V,7V-dimethylaniline donor 1. The donor-acceptor distances and orientations in 1 are strongly
A gene-expression screen, looking for androgen response genes in the rat ventral prostate, has identified adrenomedullin (AM), a 52-amino acid pluripotent peptide hormone, first isolated from pheochromocytoma. Northern blot analysis demonstrates that the level of expression in the prostate is reduced at least 25-fold by castration, with the majority of the decrease occurring in the first day, and that androgen replacement in seven-day castrated rats stimulates expression to supernormal levels, with the majority of the increase occurring within 14 h. The level of expression in the prostate is at least 50-fold higher than in the adrenal gland and cardiac atria, tissues previously reported to have the highest level of expression in the rat. In prostate organ culture, androgen was able to induce AM expression; and this induction resists protein synthesis inhibition, indicating that AM is a direct androgen response gene in the prostate. In situ hybridization of normal rat prostate tissue showed that AM expression is localized in the epithelial cells. Our analysis demonstrates that AM, a multifunctional peptide hormone, is abundantly expressed and directly regulated by androgen in the prostate epithelial cells. Thus, AM has the potential to play a crucial function in androgen action in the prostate.
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