Die bakterielle Signalverarbeitung am Beispiel des Sucrose Phosphotransferasesystems in Escherichia coli : Modellierung und experimentelle Überprüfung

Doctoral thesis (2003)

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase ... [more ▼]

Bacterial signal processing was investigated concerning the sucrose phosphotransferase system (sucrose PTS) in the bacterium Escherichia coli as an example. The about 20 different phosphotransferase systems (PTSs) of the cell fulfil besides the transport of various carbohydrates, also the function of one signal processing system. Extra- and intracellular signals are converted within the PTS protein chain to important regulatory signals affecting e.g. carbon metabolism and chemotaxis. A detailed dynamical model of the sucrose PTS was developed describing transport and signal processing function. It was formulated using a detailed description of complex formation and phosphate transfer between the chain proteins. Model parameters were taken from literature or were identified with own experiments. Using a formal algorithm including cluster analysis, PTS and glycolysis could be identified as biological functional units with limited autonomy. Simulation studies together with experimental hints showed that the dynamic behaviour of phosphate transfer in the PTS runs within one second. Therefore a description of steady state characteristics is sufficient for describing the signaling properties of the sucrose PTS. A steady state characteristic field describes the degree of phosphorylation of the PTS protein EIIACrr as a function of the input variables extracellular sucrose concentration and intracellular PEP:pyruvate ratio. The model has been validated with different experiments performed in a CSTR using an sucrose positive Escherichia coli W3110 derivative. A method for determining intracellular metabolite concentrations has been developed. A sample preparation technique using a boiling ethanol buffer solution was successfully applied. The PTS output signal degree of phosphorylation of EIIACrr was also measured. Steady state conditions with varying dilution rate and dissolved oxygen concentration and dynamical variations applying different stimuli to the culture were considered. Pulse, and stop feeding experiments with limiting sucrose concentrations were performed. Simulation and experimental results matched well. The same holds for the expanded sucrose PTS and glycolysis model. [less ▲]

Global analysis of piecewise linear systems using impact maps and quadratic surface Lyapunov functions

in IEEE Transactions on Automatic Control (2003), 48(12), 2089-2106

This paper presents an entirely new constructive global analysis methodology for a class of hybrid systems known as piecewise linear systems (PLS). This methodology infers global properties of PLS solely ... [more ▼]

This paper presents an entirely new constructive global analysis methodology for a class of hybrid systems known as piecewise linear systems (PLS). This methodology infers global properties of PLS solely by studying the behavior at switching surfaces associated with PLS. The main idea is to analyze impact maps, i.e., maps from one switching surface to the next switching surface. Such maps are known to be “unfriendly” maps in the sense that they are highly nonlinear, multivalued, and not continuous. We found, however, that an impact map induced by an linear time-invariant flow between two switching surfaces can be represented as a linear transformation analytically parametrized by a scalar function of the state. This representation of impact maps allows the search for surface Lyapunov functions (SuLF) to be done by simply solving a semidefinite program, allowing global asymptotic stability, robustness, and performance of limit cycles and equilibrium points of PLS to be efficiently checked. This new analysis methodology has been applied to relay feedback, on/off and saturation systems, where it has shown to be very successful in globally analyzing a large number of examples. In fact, it is still an open problem whether there exists an example with a globally stable limit cycle or equilibrium point that cannot be successfully analyzed with this new methodology. Examples analyzed include systems of relative degree larger than one and of high dimension, for which no other analysis methodology could be applied. This success in globally analyzing certain classes of PLS has shown the power of this new methodology, and suggests its potential toward the analysis of larger and more complex PLS. [less ▲]

A framework for designing transgenic crops - science, safety, and citizen’s concerns.

in Nature Biotechnology (2003), 21(11), 1274-1279

Comprendre la trajectoire scolaire : l’influence des processus intra-familiaux et de l’engagement parental. Une approche transversale et longitudinale

Doctoral thesis (2003)

Certification logicielle de Calcul Global avec dépendances sur grille

in Proc. des 15èmes rencontres francophones du parallélisme (RenPar'15) (2003, October)

Täter-Opfer-Konstellationen und Interaktionen im Bereich fremdenfeindlicher, rechtsextremistischer und antisemitischer Gewaltdelikte. Eine Auswertung auf Basis quantitativer und inhaltsanalytischer Analysen polizeilicher Ermittlungsakten sowie von qualitativen Interviews mit Tätern und Opfern in NRW. Kurzbericht

Report (2003)

Zur Wirkung externaler versus internaler Aufmerksamkeitsfoki beim Erlernen einer Bewegungsfertigkeit mit proximalem Effekt

in Krug, Jürgen; Müller, Thomas (Eds.) Messplätze - Messplatztraining - Motorisches Lernen (2003, October)

Was macht Personbeschreibungen kohärent?

Scientific Conference (2003, September)

„Kleider machen Leute“. Die äußere Erscheinung als Attribut von Personkategorien

Scientific Conference (2003, September)

Book review: ‘How much risk? A guide to understanding environmental health hazards' by Inge F. Goldstein and Martin Goldstein

Article for general public (2003)