Enhanced Diffusion and Chemotaxis of Catalytically Active Enzymes
Par Pierre Illien, Physicochimie des Electrolytes et Natosystèmes interfaciaux, Laboratoire PHENIX, Sorbonne Université, Paris
Mardi 28 Mai, 14h00, Salle des séminaires (215), 2ème étage, Bâtiment A4N
Abstract :
Because of their biocompatibility and ubiquity, enzymes have been extensively studied in recent years as ideal models for nanomachines. It has been reported that enzymes undergo enhanced diffusion in the presence of their corresponding substrate, when this substrate is uniformly distributed in solution. Moreover, if the concentration of the substrate is non-uniform, enzymes and other small molecules have been reported to show chemotaxis, namely biased movement in the direction of the substrate gradient. However, the underlying physical mechanisms responsible for enhanced diffusion and chemotaxis at the nanoscale are still not well understood. We will review the available experimental observations of both enhanced diffusion and chemotaxis, and discuss critically the different theories that have been proposed to explain the two. We put particular emphasis on an equilibrium model which describes how the diffusion of dumbbell-like modular enzymes can be enhanced in the presence of substrate, thanks to a binding-induced reduction of the internal fluctuations of the enzyme. We then turn to chemotaxis, and discuss a microscopic model for chemotaxis including both non-specific interactions and binding between enzyme and substrate, which is consistent with the experimental observations of chemotaxis.