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Stability and cost optimality of power generation and supply systems must not be considered independently from one another. Simple examples show that optimizing cost without considering stability may result in modes of operation that, while economically optimal, are unstable. We demonstrate that stability, robustness, and optimality can be considered systematically and simultaneously by combining bifurcation theory and nonlinear optimization. Essentially, the proposed method enforces a backoff distance between the optimal point of operation and operational or stability boundaries in the space of the optimization variables, where bifurcation theory is used to describe nonlinear stability boundaries.
Wechselwirkungen zwischen Druckluftspeichern und Netzengpässen in zukünftigen Energiesystemen
(2013)
Despite their overwhelming complexity, living cells display a high degree of internal mechanical and functional organization which can largely be attributed to the intracellular biopolymer scaffold, the cytoskeleton. Being a very complex system far from thermodynamic equilibrium, the cytoskeleton's ability to organize is at the same time challenging and fascinating. The extensive amounts of frequently interacting cellular building blocks and their inherent multifunctionality permits highly adaptive behavior and obstructs a purely reductionist approach. Nevertheless (and despite the field's relative novelty), the physics approach has already proved to be extremely successful in revealing very fundamental concepts of cytoskeleton organization and behavior. This review aims at introducing the physics of the cytoskeleton ranging from single biopolymer filaments to multicellular organisms. Throughout this wide range of phenomena, the focus is set on the intertwined nature of the different physical scales (levels of complexity) that give rise to numerous emergent properties by means of self-organization or self-assembly.
Synthesis and release of the bacterial compatible solute 5-hydroxyectoine in Hansenula polymorpha
(2013)
Ectoine and 5-hydroxyectoine belong to the family of compatible solutes which are known to mainly contribute to the adaptation of the cell to osmotic stress by mediation of a constant turgor. In addition the cell's essential functions are maintained under stress conditions like high salinity, heat or aridity stress. Hansenula polymorpha was engineered to catalyze the transformation of monomeric substrates to 5-hydroxyectoine. For this purpose four genes encoding the enzymes of the 5-hydroxyectoine biosynthesis pathway of Halomonas elongata, EctA, EctB, EctC, and EctD, were inserted into the genome of H. polymorpha. Subsequently the syntheses of ectoine and 5-hydroxyectoine were analyzed and optimized. We showed that H. polymorpha is a suitable system for recombinant 5-hydroxyectoine synthesis in gram per liter scale (2.8 g L⁻¹ culture supernatant, 365 μmol/g dcw) in which almost 100% conversion of ectoine to 5-hydroxyectoine without necessity of high salinity were achieved.
The literature as well as databases are ambiguous about the exact start of human interleukin-6 (IL-6)--three possibilities for the initiation of the mature protein are described. These three variants of IL-6, different in the exact initiation of the mature protein (A28, P29, or V30), were expressed in Hansenula polymorpha using the Saccharomyces cerevisiae MFα prepro sequence instead of the homologous pre sequence. All three IL-6 variants were secreted but the processing by the Kex2 protease showed significant differences. V30-IL-6 showed correctly processed material but also a molecule species of higher molecular weight indicating incomplete processing of the MFα pro peptide. P29-IL-6 did not yield any correctly processed IL-6, instead only the unprocessed pro form was found in the culture supernatant. Only A28-IL-6 led to 100% correctly processed material. N-terminal sequencing of this material revealed a start at V30--obviously the first two amino acids (Ala28-Pro29) have been removed by a so far unknown protease. Thus expression of both A28-IL-6 and V30-IL-6 as MFα prepro fusion proteins resulted in the very same mature V30-IL-6, however, the ratio of correctly processed molecules was significantly higher in the case of A28-IL-6. The expression of an MFα prepro-interferon α-2a (IFNα-2a) fusion protein in H. polymorpha leads to about 50% correctly processed molecules and 50% misprocessed forms which contain part of the pro peptide at the N-termini. The insertion of A28 and P29 of IL-6 between the pro peptide and the start of the mature IFNα-2a led to correct processing and elimination of all high molecular weight isoforms observed in earlier experiments.
In Zeiten zunehmender Marktdynamik und kürzer werdender Innovationszyklen fragen sich viele Unternehmen: Wie können wir das kreative Potenzial unserer eigenen Mitarbeiter besser nutzen? Denn es gibt sie in jeder Organisation: Leute, die das radikal Neue nicht nur denken, sondern auch umsetzen wollen.