Application of an enzyme thermistor for the determination of glucose in complex fermentation media

An enzyme thermistor was used for on-line glucose determination during cultivation of Cephalosporium acremonium for a period of 160 h. The complex medium consisted of 100 g 1^?1 peanut meal. Automatic control and data registration were achieved by interfacing a process computer with the thermistor unit. Problem caused by long-term application are discussed. On-line and off-line data obtained with the enzyme thermistor are compared with the results obtained with a commercial glucose analyzer. The results of these experiments show that an enzyme thermistor can be used to determine glucose concentration in complex fermentation media under real cultivation conditions for about 60 h.     

Tunable,narrow-band picosecond radiation in the mid-infrared by difference frequency mixing in GaSe and CdSe

We report on the generation of tunable, narrow-band picosecond laser pulses in the mid-IR at 1 kHz repetition rate. An optical parametric oscillator (OPO) seeded optical parametric amplifier (OPA) delivers signal and idler pulses with energies of several hundred microjoule tunable between 1.56 and 3.24 m. Difference frequency mixing of the OPA signal and idler waves permits the generation of mid-IR radiation between 3 and 24 m. The laser system therefore permits full coverage of the wavelength range between 1.6 and 24 m. Conversion efficiencies greater than 50% and pulse energies up to 40 J are obtained with GaSe. PACS 42.65.Re; 42.65.Yj; 42.72.Ai     

An improved method for the synthesis of [closo-B12(OH)12]-2

The dicesium salt of the icosahedral borane anion dodecahydroxy-closo-dodecaborate(2-), closo-Cs(2)B(12)(OH)(12), Cs(2)4, was prepared using an improved synthetic pathway. Heating cesium dodecahydro-closo-dodecaborate, closo-Cs(2)B(12)H(12), Cs(2)1, with 30% hydrogen peroxide added in successive increments at 105-110 degrees C provided Cs(2)4 in 95% yield. Reaction progress was monitored using (1)H-decoupled (11)B NMR while (17)O NMR provides the most reliable way to detect the presence of peroxides in the reaction solution. The reaction may be safely increased in scale to afford Cs(2)4 in multigram quantities.     

Rationally designed ligands for asymmetric iridium-catalyzed hydrogenation of olefins

A new class of chiral N,P-ligands for the Ir-catalyzed asymmetric hydrogenation of aryl alkenes has been developed. These new ligands proved to be highly efficient and tolerates a broad range of substrates. The enantiomeric excesses are in the range of the best ever reported. The results can be rationalized with the proposed selectivity model.     

Monitoring of protein profiles for the optimization of recombinant fermentation processes using public domain databases

The expression of human superoxide dismutase in fed-batch fermentation of E. coli HMS174(DE3)(pET3ahSOD) was studied as model system. Due to the frequently used strong T7 promoter system a high metabolic load is exerted, which triggers stress response mechanisms and finally leads to the differentiation of the host cell. As a consequence, host cell metabolism is partly shifted from growth to survival accompanied by significant alterations of the protein pattern. In terms of process optimization two-dimensional electrophoresis deserves as a powerful tool to monitor these changes on protein level. For the analysis of samples derived from different states of recombinant protein production wide-range Immobiline Dry Strips pH 3-10 were used. In order to establish an efficient procedure for accelerated process optimization and to avoid costly and time-consuming analysis like mass spectrometry (MS), a database approach for the identification of significant changes of the protein pattern was evaluated. On average, 935 spots per gel were detected, whereby 50 are presumably stress-relevant. Out of these, 24 proteins could be identified by using the SWISS-2DPAGE database (www.expasy.ch/ch2d/). The identified proteins are involved in regulatory networks, energy metabolism, purine and pyrimidine nucleotide synthesis and translation. By this database approach, significant fluctuations of individual proteins in relation to recombinant protein production could be identified. Seven proteins show strong alterations (>100%) directly after induction and can therefore be stated as reliable marker proteins for the assessment of stress response. For distinctive interpretation of this highly specific information, a bioinformatic and statistic tool would be essential in order to perceive the role and contribution of individual proteins in stress response.     

Wave-vector-dependent exciton exchange interaction

The exchange interaction for the yellow 1S orthoexciton in Cu2O is derived up to the order K2. The resulting exchange splittings are verified experimentally using high resolution spectroscopy. In agreement with theory the fine structure shows a characteristic dependence on the direction of the wave vector.     

Signs in the -index of Eulerian partially ordered sets

A graded partially ordered set is Eulerian if every interval has the same number of elements of even rank and of odd rank. Face lattices of convex polytopes are Eulerian. For Eulerian partially ordered sets, the flag vector can be encoded efficiently in the -index. The -index of a polytope has all positive entries. An important open problem is to give the broadest natural class of Eulerian posets having nonnegative -index. This paper completely determines which entries of the -index are nonnegative for all Eulerian posets. It also shows that there are no other lower or upper bounds on -coefficients (except for the coefficient of ).