Proteins as micro viscosimeters: Brownian motion revisited
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Updated: Aug 9, 2026

Study of Protein Dynamics via Neutron Spin Echo Spectroscopy
Published on: April 13, 2022
Daniel Lavalette1, Mark A Hink, Martine Tourbez
1Institut Curie-Recherche, Bâtiment 112, Centre Universitaire, 91405, Orsay, France. daniel.lavalette@curie.u-psud.fr
Abstract:
Translational and rotational diffusion coefficients of proteins in solution strongly deviate from the Stokes-Einstein laws when the ambient viscosity is induced by macromolecular co-solutes rather than by a solvent of negligible size as was assumed by A. Einstein one century ago for deriving the laws of Brownian motion and diffusion. Rotational and translational motions experience different micro viscosities and both become a function of the size ratio of protein and macromolecular co-solute. Possible consequences upon fluorescence spectroscopy observations of diffusing proteins within living cells are discussed.
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