CONICET | Buscador de Institutos y Recursos Humanos

The reaction confinement to dimensionally restricted spaces such as percolation matrix or a surface, like a cellular environmetns, can cause significant effects on reaction mechanism and rate. The accompanying molecualr crowding may be affecting the probability of enzyme-substrate collisions due to excluded volume and the thermodynamic actiuvity of water due to its structuring at surfaces. Monomolecualr reactions are not affected by dimensionally restrictions due to their unitary kinetic order. This is a reasonable assumption because, in these cases, dimensionally restrictions are not expected to affect the probability that an isolated molecule exhibits spontaneous cleavage or conformational change. However, dimensionally restrictions have a greater influence in collision probabilities and, hence, in the rate of a bimolecular reaction. A fractal kinetics may arise in restricted reacrtion conditions when the potential-energy surface that has to be explored during the reaction possesses fractal properties. In those cases, kinetic orders will reflect the fractal dimension of the surface where the reaction is taking place. In both conditions, protein structure and function can also be affected. Under this hypothesis, we studied the structure/activity relationship of two proteins. One of them was an aqueous soluble protein (beta-galactosidase) bound to a lipid water interface and rhe other one was a membrane-anchored protein (placental alkaline phosphatase) which in natural conditions is immersed in the molecular crowded environment of the cellular glycocalix. In both cases we used Langmuir and Langmuir-Blodgett films as a membrane models, with or without a pseudo-glycocalix and evaluated protein conformation and activity. Across-talk between protein and environmental structure was evidenced through kinetics

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