ABSTRACT
In this article, the model of a simple kinetic reaction process with an oscillating change in enzyme activity modulated by cosine-like function is considered. The model includes one substrate and one intermediate product in the reversible and irreversible enzymatic processes. The results obtained by numerical solutions show the small oscillations of enzyme-substrate complex with the phase shift in the steady state with respect to the oscillatory activity of enzyme. This phase shift decreases and tends to zero in dependence on the increasing activity of the enzyme periodic action. The presented model may refer to many enzymatic catalyzed reactions occurring in living organisms.
Subject(s)
Apocynaceae/enzymology , Enzymes/metabolism , Models, Biological , Catalysis , Kinetics , Luciferases/metabolism , Methyltransferases/metabolismABSTRACT
The influence of heating time and pressurizing time under pressure of 1 GPa on radicals generation in potato starch polymer was investigated by EPR. Potato starch was heated at two temperatures: 413 ± 2 K (140 °C) and 473 ± 2 K (200 °C) for 15, 30, 60, 120, 180, 240, 270 and 300 min and subdued to pressurizing under pressure of 1 ± 0.002 GPa for 6, 60, 300 and 1440 min. In starch heated at 413 K (140 °C) a decrease in the relative intensity of the EPR signal as a function of the pressurizing time can be observed, whereas in starch heated at 473 K (200 °C) such a decrease is not observed. The EPR spectra analysis indicates that they are powder spectra due to the paramagnetic centers leading to Lorentzian line shapes with weak spectroscopic splitting factor g anisotropies and linewidth anisotropies. We have shown that pressurization of starch causes a decrease in the number of radicals in a temperature range in which the polymer is not yet disintegrated. The results of the EPR investigations indicate the existence of a carbon radical center situated at the carbon C1 of the glucose ring. In the EPR spectra of the samples heated with no oxygen access, the hyperfine structure is poorly visible. In the registered EPR spectra of the samples heated with oxygen access, the hyperfine structure is not observed.
Subject(s)
Free Radicals/chemistry , Solanum tuberosum , Starch/chemistry , Electron Spin Resonance Spectroscopy , Hot Temperature , Pressure , Time FactorsABSTRACT
The X-band EPR study of a polycrystalline Cs2Cu(ZrF6)2*6H2O demonstrates a feature of plasticity of the Jahn-Teller Cu(H2O)6 complex in the crystal lattice of this compound. The temperature- and pressure-induced evolution of the spectra shows that the copper complex is extremely sensitive to these factors, which due to the ferroelastic properties of the compound studied modify the internal tetragonal and orthorhombic strains acting on the complex. It is supported by the analysis of the temperature dependencies of the principal values of the g-factor under various pressures, indicating that the complex varies its shape adapting it to the varied conditions. A pressure-induced phase transition is discovered.
