  Liquid-liquid phase separation (LLPS) of protein solutions is governed by
highly complex protein-protein interactions. Nevertheless, it has been
suggested that based on the extended law of corresponding states (ELCS), as
proposed for colloids with short-range attractions, one can rationalize not
only the thermodynamics, but also the structure and dynamics of such systems.
This claim is systematically and comprehensively tested here by static and
dynamic light scattering experiments. Spinodal lines, the isothermal osmotic
compressibility $\kappa_\text{T}$ and the relaxation rate of concentration
fluctuations $\Gamma$ are determined for protein solutions in the vicinity of
LLPS. All these quantities are found to exhibit a corresponding-states
behavior. This means that, for different solution conditions, these quantities
are essentially the same if considered at similar reduced temperature or second
virial coefficient. For moderately concentrated solutions, the volume fraction
$\phi$ dependence of $\kappa_\text{T}$ and $\Gamma$ can be consistently
described by Baxter's model of adhesive hard spheres. The off-critical,
asymptotic $T$ behavior of $\kappa_\text{T}$ and $\Gamma$ close to LLPS is
consistent with the scaling laws predicted by mean-field theory. Thus, the
present work aims at a comprehensive experimental test of the applicability of
the ELCS to structural and dynamical properties of concentrated protein
solutions.
