Effective charge of bovine serum albumin determined by electrophoresis NMR

The effective charge of bovine serum albumin in aqueous solution is determined by dynamic NMR as a function of pH. The effective charge results from the degree of dissociation varying with pH and the local counterion condensation. While the hydrodynamic friction is determined from the diffusion coefficient measured by pulsed-field gradient NMR, the electrophoretic mobility is determined by electrophoresis NMR. The effective charge per molecule is calculated from the force balance between hydrodynamic friction and force in the electric field acting on the charges. Since it is influenced by counterion condensation it is smaller than the net charge from titration.

From a combination of diffusion and electrophoresis NMR the effective charge of BSA has been determined as a function of pH from the balance between hydrodynamic friction and force in the electric field. It describes the charge of the molecule interacting with other molecules or an external field.