Alexei Lapin

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The transduction of signals depends on the translocation of signaling molecules to specific targets. Undirected diffusion processes play a key role in the bridging of spaces between different cellular compartments. The diffusion of the molecules is, in turn, governed by the intracellular architecture. Molecular crowding and the cytoskeleton decrease(More)
We investigate a three-dimensional multiscale model of vascular tumour growth, which couples blood flow, angiogenesis, vascular remodelling, nutrient/growth factor transport, movement of, and interactions between, normal and tumour cells, and nutrient-dependent cell cycle dynamics within each cell. In particular, we determine how the domain size, aspect(More)
Selenium accumulation and the growth of cyanobacterium Spirulina platensis (Nordst.) Geitl. were studied in a culture with sodium selenite-supplemented nutritional medium. Selenite concentrations below 20 mg/l did not inhibit the growth of S. platensis. The addition of 30 mg/l of this salt somewhat decreased the growth rate during the linear growth phase,(More)
In this paper we apply a novel agent-based simulation method in order to model intracellular reactions in detail. The simulations are performed within a virtual cytoskeleton enriched with further crowding elements, which allows the analysis of molecular crowding effects on intracellular diffusion and reaction rates. The cytoskeleton network leads to a(More)
Agent-based models are rigorous tools for simulating the interactions of individual entities, such as organisms or molecules within cells and assessing their effects on the dynamic behavior of the system as a whole. In context with bioprocess and biosystems engineering there are several interesting and important applications. This contribution aims at(More)
A method is proposed for identification of kinetic parameters when diffusion of substrates is limiting in reactions catalyzed by immobilized enzymes. This method overcomes conventional sequential procedures, which assume immobilization does not affect the conformation of the enzyme and, thus, consider intrinsic and inherent kinetics to be the same. The(More)
* Corresponding author: Tel.: ++49 (0)711 68565036; Fax: ++49 (0)711 685; Email: 1 Center Systems Biology, University of Stuttgart, Germany 2 OCCAM and Department of Computer Science, University of Oxford, United Kingdom 3 H. Lee Moffitt Cancer Center and Research Institute, Tampa, United States of America 4 Centre de Recerca Matemàtica,(More)
The effect of efficiency improvement of chromatographic system by injecting a sample at a lower carrier gas velocity (in comparison with the carrier gas velocity at subsequent separation) was studied experimentally and theoretically in isothermal gas-liquid chromatography. The suggested technique is based on sample introduction in the programmed carrier gas(More)
Chlorimipramine and other tricyclic antidepressant drugs are widely used for the treatment of depressive disorders. We analysed chlorimipramine and its major metabolite desmethylchlorimipramine after a two step extraction from plasma with diethylether. The underivatized samples were separated on a short (40 cm x 2 mm) silanized glass column packed with 3%(More)
A method for the sensitive and selective determination of glycine in brain tissue has been developed. Small samples of brain tissue were homogenized by sonication in 0.7 N formic acid, and [1,2 13C2,15N]glycine was then added as internal standard. After centrifugation, aliquots of the supernatants were dried and the resulting residues were derivatized in a(More)