Dynamic Light Scattering

 The diffusion coefficient can best be obtained from a dynamic light scattering study (also known as quasi-elastic light scattering; photon correlation spectroscopy; intensity fluctuation spectroscopy). The concentration of solution needed is highly dependent on the molecular mass of the sample: scattering intensity is simplistically proportional to the square of the mass. As a guide, a minimum concentration of 1+ mg/ml is needed for BSA. Samples can be run either on the Protein Solutions P-801 single angle instrument) or on the Malvern multi-angle system.

The Protein Solutions DP-801 dynamic light scattering instrument used in the Centre has built-in temperature control and measures the scattered light at 90° to the incident light beam. It requires very small sample volumes (of the order of 50µL) and measurement and analysis are fully automated. It is most suitable for globular proteins for which 10k Da < M < 200k Da.

Another instrument, The Malvern 4700c is also available through the main NCMH Laboratory. It uses much larger sample volumes (2-3 mL) and has variable detector geometry for angular dependence measurement. This machine is suitable for larger or more asymmetric systems.