Hydrodynamic analysis of macromolecular conformation.: A comparative study of flow field flow fractionation and analytical ultracentrifugation

A study of the retention and separation of several proteins with various geometries from spheres to elongated conformations and xanthan gum in its rodlike conformation by asymmetrical now field now fractionation (aF-FFF) is presented, The obtained data are compared with those from analytical ultracentrifugation (AUC) as a hydrodynamic reference method. The data are discussed within the framework of hydrodynamics and thermodynamics. The results clearly show the failure of FFF to yield the exact geometries of particles differing from spherical shape due to a wrong determined diffusion coefficient for asymmetrical particles. The deviation from the AUC results becomes more pronounced with increasing asymmetry. However, FFF can show a higher resolution than AUC if the samples exhibit a density distribution which is demonstrated for ferritin.