Along with polyisoprenoids, polypeptides, polysaccharides, and polynucleotides, Nature contains a further group of biopolymers, the poly(hydroxya1kanoates). The commonest member of this group, poly[ (R)-3-hydroxybutyrate] P(3-HB), had been identified by Lemoigne as early as the 1920s, as a storage substance in the microorganism Bacillus megaterium made up of more than 12000 (3-HB) units. However, the widespread distribution and significance of these biopolymers has only become clear recently. The work of Reusch, in particular, has shown that low molecular weight P(3-HB) (100-200 3-HB units) occurs in the cell membranes ofprokaryotic and eukaryotic organisms. The function of P(3-HB) in the latter sources is largely unknown; it has been proposed that a complex of P(3-HB) and calcium polyphosphate acts as an ion channel through the membrane. Indeed, it has even been speculated that P(3-HB) plays a role in transport of DNA through the cell wall. In the present article, the following subjects will be discussed : metabolism of P(3-HB) and analogous polyesters in the synthesis and degradation of storage materials ; P(3-HB) as a starting material for chiral synthetic building blocks; synthesis of cyclic oligomers (oligolides) of up to ten 3-HB units, and their crystal structure; high molecular weight bio-copolymers of hydroxybutyrate and hydroxyvalerate (BIOPOL) as biologically degradable plastics; nonbiological production of polyhydroxyalkanoates from 3-hydroxy carboxylic acids and the corresponding p-lactones; specific synthesis of linear oligomers with a narrow molecular weight distribution, consisting of about 100 (R)-3-hydroxybutyrate units, by using an exponential coupling procedure; structure of the polyesters, and a comparison with other polymers; the experimental results which led to the postulation of a P(3-HB) ion channel through the cell wall; modeling of P(3-KB) helices of various diameters, by using the parameters obtained from the crystal structures of oligolides; formation of a crown ester complex and ion transport experiments with the triolide of 3-HB. The article describes one example of the contributions that synthetic organic chemists can make to important biological problems in an interdisciplinary framework.

A total of 220 samples comprising cereals, cereal byproducts, corn plants and corn silage as well as non-grain based feedstuffs was randomly collected during 2000 and 2001 from sources located in Germany and analysed for 16 Fusarium toxins. The trichothecenes scirpentriol (SCIRP), 15-monoacetoxyscirpenol (MAS), diacetoxyscirpenol (DAS), T-2 tetraol, T-2 triol, HT-2 and T-2 toxin (HT-2, T-2), neosolaniol (NEO), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivealenol (15-ADON), nivalenol (NIV) and fusarenon-X (FUS-X) were determined by gas chromatography/mass spectrometry. Zearalenone (ZEA) and alpha- and beta-zearalenol (alpha- and beta-ZOL) were analysed by high performance liquid chromatography with fluorescence and UV-detection. Detection limits ranged between 1 and 19 microg/kg. Out of 125 samples of a group consisting of wheat, oats, corn, corn byproducts, corn plants and corn silage only two wheat samples did not contain any of the toxins analysed. Based on 125 samples the incidences were at 2-11% for DAS, NEO, T-2 Triol, FUS-X, alpha- and beta-ZOL, at 20-22% for SCIRP, MAS, T-2 tetraol and 3-ADON, at 44-74% for HT-2, T-2, 15-ADON, NIV and ZEA, and at 94% for DON. Mean levels of positive samples were between 6 and 758 microg/kg. Out of 95 samples of a group consisting of hay, lupines, peas, soya meal, rapeseed meal and other oil-seed meals, 64 samples were toxin negative. DAS, T-2 triol, NEO and FUS-X were not detected in any sample. The incidences of DON and ZEA were at 14 and 23% respectively, those of the other toxins between 1-4%, mean levels of positive samples were between 5 and 95 microg/kg.

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We report on a cladding-pumped, ytterbium-doped large-core-area fiber amplifier that is capable of generating 51.2 W of average power at a 1064-nm center wavelength, an 80-MHz repetition rate, and a 10-ps pulse duration. In an ytterbium-doped large-mode-area fiber these pulses could be amplified up to 43.2 W with diffraction-limited beam quality (M(2)~1.3) . Power scaling limitations that arise from nonlinear distortions such as self-phase modulation and stimulated Raman scattering are discussed.

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