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In this paper the X-ray structure and magnetic properties of iron(II) acetate -starting material for the synthesis of a wide range of iron complexes -are presented. The compound crystallises in the space group Pbcn and was identified as 2D coordination polymer consisting of iron atoms and acetate moieties with all the iron atoms hexacoordinate and different coordination modes for the acetate moieties. Additional hydrogen bond contacts lead to a porous coordination polymer

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Cells of Saccharomyces cerevisiae exhibiting the a mating type secrete into the culture medium a mating-type-specific hormone activity ( a factor), which specifically causes a transient arrest of DNA replication and cell division in cells of the opposite mating type, a. Three compounds exhibiting a factor activity have been found in culture filtrates from a cells. The most active compound has been purified more than 105-fold and appears to be homogeneous on the basis of thinlayer chromatography and thin-layer electrophoresis in different systems. We propose that this compound, which exhibits in a cells the biological activities that have been attributed to a factor, represents pure a factor. a factor has been characterized as a very hydrophobic undecapeptide with the following amino acid composition: HzN-Tyr (Asxl, Glyt, Alal, Vall, Ilez, Phel, Lysl, Trpl, Prol). Although in their respective targct cclls thc biological effects of a factor and of a factor, the corresponding mating hormone of mating-type-a cells, are remarkably similar, the primary structures of both hormones appear to be quite different.

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Conjugation between haploid cells of Saccharomnyces ceretisiae is mediated through the action of diffusible mating hormones, two of which have been designated as a-factor and a-factor. Partially purified fractions exhibiting afactor activity have been obtained from culture filtrates of a cells by ultrafiltration, ion-exchange chromatography, and gel filtration. The a-factor preparations specifically caused both Gi arrest and morphological alterations in cells of a-mating type, whereas a cells, a/a diploids, and nonmating a mutants were not affected. The a-factor activity was found in the culture filtrates of all a strains tested, but not in filtrates of a or a/a cell cultures. The hormone is sensitive to various proteases, showing that it is associated with a peptide or protein. Gel filtration studies suggest an apparent molecular weight >600,000; however, this result may be due to aggregation with carbohydrate present in the preparations. Although the biological activities of a-factor are analogous to those described previously for a-factor, the chemical properties of these two hormones appear to be quite different.

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