  The concept of the surface of a protein in solution, as well of the interface
between protein and 'bulk solution', is introduced. The experimental technique
of small angle X-ray and neutron scattering is introduced and described
briefly. Molecular dynamics simulation, as an appropriate computational tool
for studying the hydration shell of proteins, is also discussed. The concept of
protein surfaces with fractal dimensions is elaborated. We finish by exposing
an experimental (using small angle X-ray scattering) and a computer simulation
case study, which are meant as demonstrations of the possibilities we have at
hand for investigating the delicate interfaces that connect (and divide)
protein molecules and the neighboring electrolyte solution.
