[show abstract][hide abstract] ABSTRACT: We present a new model for calcium oscillations based on experiments in hepatocytes. The model considers feedback inhibition on the initial agonist receptor complex by calcium and activated phospholipase C, as well as receptor type-dependent self-enhanced behavior of the activated G(alpha) subunit. It is able to show simple periodic oscillations and periodic bursting, and it is the first model to display chaotic bursting in response to agonist stimulations. Moreover, our model offers a possible explanation for the differences in dynamic behavior observed in response to different agonists in hepatocytes.
[show abstract][hide abstract] ABSTRACT: A spatially extended model of diffusively coupled (bio)chemical oscillators creates spatio-temporal disorder (hyperchaos) characterized by complex and weakly correlated concentration patterns in space and time. Applying different types of local stimulation we show that the system forms stable patterns with well-defined global order for certain windows of parameters. Spatio-temporal hyperchaos thus supports efficient pattern control with minimum effort. A possible relevance of this mechanism for experimentally observed calcium wave patterns is pointed out.
The Journal of Chemical Physics 01/1999; 110:3251-3255. · 3.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report current oscillations during the potentiostatic oxidation of iodide in aqueous solution. The oscillations become visible as columns of descending liquid with periodic structure colored by iodine (or iodine−starch complex). They can be attributed to a periodically varying flow of solution in front of the electrode due to a density gradient. The instability is explained using a qualitative model with a threshold function for the onset of the flow.
Journal of Physical Chemistry A - J PHYS CHEM A. 12/1998; 103(1).
[show abstract][hide abstract] ABSTRACT: The kinetics of the peroxidase-catalyzed oxidation of iodide was found to be strongly nonlinear under certain conditions. At slightly acidic pH, the reaction behaves like an enzymatic “iodine clock”, i.e., the reaction is switched on after a well-defined time depending on the initial concentrations of the reactants. This behavior is studied experimentally and is shown to represent a true dynamic enzymatic switch. Numerical simulations of a mechanistic model strengthen this conclusion.
Journal of Physical Chemistry A - J PHYS CHEM A. 06/1998; 102(29).
[show abstract][hide abstract] ABSTRACT: The effect of various phenols and aromatic amines on the dynamics of the peroxidase-catalyzed aerobic oxidation of NADH was investigated. We demonstrate that several aromatic compounds may substitute for 2,4-dichlorophenol in inducing sustained oscillations and complex dynamics in the reaction. These aromatic compounds can also act as substrates in the classical peroxidase reaction. Since some of the aromatic compounds studied are naturally occurring substrates for peroxidases, we conjecture that oscillations and complex dynamics may well occur in the intact plant.
Journal of the American Chemical Society 03/1997; 119:2084. · 10.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: The nonlinear behavior of the peroxidase-oxidase reaction was studied using structurally different peroxidases. For the first time sustained oscillations with peroxidases other than horseradish peroxidase in a single-enzyme system were observed. All peroxidases that showed significant oxidase activity were able to generate sustained oscillations. When adjusting the overall reaction rate, either of the two modifiers 2,4-dichlorophenol or Methylene blue could be omitted from the reaction. Due to the observation of different enzyme intermediates when using different peroxidases, we conclude that the mechanisms responsible for oscillatory kinetics may vary from one peroxidase to the other.
Biochimica et Biophysica Acta 05/1996; 1289(3):397-403. · 4.66 Impact Factor