The shock of the old: hydrodynamics for the masses.

Hydrodynamic techniques such as analytical ultracentrifugation can provide key information about subunit stoichiometry and interaction strengths of protein-nucleic acid interactions. Analysis is complicated by (i) the need for low concentrations in order to observe both free and bound species and (ii) thermodynamic non-ideality. With the introduction of fluorescence optics, we are able to obtain data at lower concentrations, and improved understanding of the statistical thermodynamics of macromolecular solutions has allowed non-ideality to be accurately assigned. With these developments, it is possible now to assay protein-nucleic acid interactions at concentrations typically used in molecular biology assays.