Effective charge and hydrodynamic size of molecules and aggregates
back to Magnetic resonance
Pulsed-field gradient NMR is applied to measure displacements like flow and diffusion. From the diffusion coefficient the hydrodynamic size is determined. Sizes from 0.1 nm to 300 nm are accessible, individual species are identified by the chemical shift in the NMR signal. Electrophoretic motion generated by the in-situ application of a DC electric field during the experiment is detected by PFG NMR. From the combination of the electrophoretic mobility and the diffusion coefficient the effective charge is calculated without further assumptions. The effective charge of macromolecules is smaller than the effective charge because of condensation of counterions, it is utilized to follow the formation of complexes.
- Böhme, U. ; Scheler, U.
Counterion condensation and effective charge of poly(styrenesulfonate)
Advances in Colloid and Interfaces Science 158 (2010) 63-67