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Dr. Yuriy Rebets Dr. Elke Brötz Niko Manderscheid Dr. Bogdan Tokovenko Dr. Maksym Myronovskyi Prof. Dr. Peter Metz Dr. Lutz Petzke Dr. Andriy Luzhetskyy 《Angewandte Chemie (International ed. in English)》2015,54(7):2280-2284
Pamamycins are macrodiolides of polyketide origin with antibacterial activities. Their biosynthesis has been proposed to utilize succinate as a building block. However, the mechanism of succinate incorporation into a polyketide was unclear. Here, we report identification of a pamamycin biosynthesis gene cluster by aligning genomes of two pamamycin‐producing strains. This unique cluster contains polyketide synthase (PKS) genes encoding seven discrete ketosynthase (KS) enzymes and one acyl‐carrier protein (ACP)‐encoding gene. A cosmid containing the entire set of genes required for pamamycin biosynthesis was successfully expressed in a heterologous host. Genetic and biochemical studies allowed complete delineation of pamamycin biosynthesis. The pathway proceeds through 3‐oxoadipyl‐CoA, a key intermediate in the primary metabolism of the degradation of aromatic compounds. 3‐Oxoadipyl‐CoA could be used as an extender unit in polyketide assembly to facilitate the incorporation of succinate. 相似文献
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Elke Baum Patrik Dahlke Volker Kaiser Michel Molinier Roland E. Schmidt Jürgen Pebler Werner Massa Dietrich Babel 《无机化学与普通化学杂志》2006,632(14):2244-2250
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A. Beckmann K. D. Böklen G. Bremer D. Elke 《Zeitschrift für Physik A Hadrons and Nuclei》1975,272(2):143-145
Using the atomic beam magnetic resonance method the Zeeman interactions of12C in the3 P 1 and3 P 2 states at magnetic fields of about 3.4 kOe have been measured. The measured quantities areg J (3 P 1)?gJ(3 P 2)=15.4(1.0)·10?6 g J (3 P 2)=1.5010616 (50), from which the following value for gJ(3P1) can be calculated:g J (3 P 1)=1.5010770 (50). The experimental results are in moderate agreement with theoretical calculations. 相似文献
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Phase biaxiality in nematic liquid crystalline side-chain polymers of various chemical constitutions
Severing K Stibal-Fischer E Hasenhindl A Finkelmann H Saalwächter K 《The journal of physical chemistry. B》2006,110(32):15680-15688
In a previous deuterium NMR study conducted on a liquid crystalline (LC) polymer with laterally attached book-shaped molecules as the mesogenic moiety, we have revealed a biaxial nematic phase below the conventional uniaxial nematic phase (Phys. Rev. Lett. 2004, 92, 125501). To elucidate details of its formation, we here report on deuterium NMR experiments that have been conducted on different types of LC side-chain polymers as well as on mixtures with low-molar-mass mesogens. Different parameters that affect the formation of a biaxial nematic phase, such as the geometry of the attachment, the spacer length between the polymer backbone and the mesogenic unit, as well as the polymer dynamics, were investigated. Surprisingly, also polymers with terminally attached mesogens (end-on polymers) are capable of forming biaxial nematic phases if the flexible spacer is short and thus retains a coupling between the polymer backbone and the LC phase. Furthermore, the most important parameter for the formation of a biaxial nematic phase is the dynamics of the polymer backbone, as the addition of a small percentage of low molar mass LC to the biaxial nematic polymer from the original study served to shift both the glass transition and the appearance of detectable biaxiality in a very similar fashion. Plotting different parameters for the investigated systems as a function of T/Tg also reveals the crucial role of the dynamics of the polymer backbone and hence the glass transition. 相似文献