A Debye-Huckel theory for electrostatic interactions in proteins

The site-site Ornstein-Zernike equation with a simple mean spherical closure is used to study electrostatic interactions of proteins. Using a Debye-Huckel approximation for the correlation functions of the bulk electrolyte and a simple basis expansion for the protein-salt direct correlation functions, we obtain a very simple variational expression for the electrostatic component of the excess chemical potential of a protein in an electrolyte solution. The predictions of the theory are tested on a model of the protein calbindin Dg,. Our calculations for calcium binding affinities and protein acidity constants are found to be in excellent agreement with the results of computer simulations. (C) 1996 American Institute of Physics.