title: A model for the calculation of the dielectric dispersion and the dipole moment of globular proteins in solution.
abstract: We describe a new procedure whereby the magnitude of the dielectric dispersion of a solution of globular protein molecules can be calculated. The protein molecule is considered to have spherical symmetry and the charged residues are thought to be situated in a medium whose dielectric constant increases continuously as a function of the distance from the centre of mass. The dipole moment of the protein in the solution is made up of two parts: the intrinsic dipole moment due to the charge distribution of the protein and the dipole moment due to polarization of the medium and the ionic cloud. When the model is applied to solutions of cytochrome c it is found that polarization of the medium results in a decrease in the dielectric dispersion amplitude. The mean square dipole moment calculated with the help of this method indicates that the fluctuation of the configurations cannot be responsible for the large dispersion in the megahertz region.
mesh_terms: D003574:Cytochrome c Group; D004563:Electrochemistry; D008433:Mathematics; D008954:Models, Biological; D011487:Protein Conformation; D011506:Proteins; D012996:Solutions
chemical_list: D003574:Cytochrome c Group; D011506:Proteins; D012996:Solutions