Modeling Equilibrium Clusters in Lysozyme Solutions
  We present a combined experimental and numerical study of the equilibrium cluster formation in globular protein solutions under no-added salt conditions. We show that a cluster phase emerges as a result of a competition between a long-range screened Coulomb repulsion and a short-range attraction. A simple effective potential, in which only depth and width of the attractive part of the potential are optimized, accounts in a remarkable way for the wavevector dependence of the X-ray scattering structure factor. 
Fr\'ed\'eric Cardinaux, Anna Stradner, Peter Schurtenberger, Francesco   Sciortino, Emanuela Zaccarelli