Hydrodynamic radius (Rh), is a parameter used to describe the size of a particle or molecule in a fluid, taking into account its shape, mass, and interactions with the surrounding fluid molecules. The hydrodynamic radius is defined as the radius of a hypothetical sphere that diffuses at the same rate as the particle or molecule in question, under the same conditions (Einstein, 1905).
The hydrodynamic radius is used to describe the behaviour of biomolecules, such as proteins, in solution. Techniques such as flow-induced dispersion analysis (FIDA) are used to determine the hydrodynamic radius experimentally. The hydrodynamic radius is a crucial parameter in drug discovery, biotechnology, and environmental science, where the behaviour of molecules in solution is essential to their function and properties
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Einstein, A. (1905). Über die von dermolekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhendenFlüssigkeiten suspendierten Teilchen. Annalen Der Physik, 322(8),549–560. https://doi.org/10.1002/andp.1905322080679