Dynamic Light Scattering
Size distributions without fractionation
Dynamic Light Scattering (DLS) measures the translational diffusion coefficients Dt of nanoparticles and colloids in solution by quantifying dynamic fluctuations in scattered light. Sizes and size distributions, in turn, are calculated from the diffusion coefficients in terms of hydrodynamic radius rh or hydrodynamic diameter dh.
DLS is suitable for ensemble measurements ranging from rh values of 0.2 nm up to 5,000 nm. Wyatt offers high-throughput, automated DLS as well as conventional, cuvette-based formats.
Applications of DLS
Here are just a few of the diverse applications supported by DLS:
- Estimate populations of aggregates large and small, for small molecules, proteins or liposomes
- Check quality of biomolecules prior to running costly analyses such as SPR or SANS
- Analyze thermal stability and chemical denaturation, differentiating pure unfolding from aggregation
- Determine sizes of metallic nanoparticles or quantum dots
- Quantify self-assembly processes of polypeptides or DNA
- Assess colloidal stability as a precursor to aggregation and precipitation
- Measure viscosity of concentrated biotherapeutics with just a few microliters of solution
DLS analysis showing a protein monomer mixed with 50 nm particulates. The size resolution of unfractionated solutions is a factor of 3-5x in radius.
DLS determines size distributions without fractionation, providing polydispersity estimates as well as hydrodynamic radii.
Dynamic Light Scattering is also known as Quasi-Elastic Light Scattering (QELS) and Photon Correlation Spectroscopy (PCS).
Automated DLS
Low-volume, automated measurements performed directly in place in standard 96-, 384- or 1536-well microwell plates reveal new horizons for dynamic light scattering. Some of the high-throughput screening tasks accomplished with the DynaPro Plate Reader II include:
- Quantifying type and degree of aggregation in hundreds of buffer conditions, important in formulation and crystallization studies
- Pre-formulation of biotherapeutic candidates to evaluate developability
- Assessment of buffer excipients and pH for colloidal stability using the diffusion interaction parameter kD
- Assessment of multiple formulations for thermal (conformational) stability using the melting temperature Tm
- Screening compound libraries for inhibition or enhancement of protein-protein interactions
- Integration of plate-based testing protocols with other kinds of plate readers
In addition, microwell-plate-based DLS is an attractive option for multi-user labs: with no costly quartz cuvettes to wash, each user can have an inexpensive, personal, disposable plate sufficient for hundreds of samples and no concern for cross-contamination with other experiments.
Melting/aggregation curve data and analyses for four proteins measured simultaneously, in triplicate, on the DynaPro Plate Reader II.
Color-coded results of measurements of three proteins, four pH conditions and 6 concentrations, with five replicates per combination, in a 384 well plate. Total measurement time was < 1.5 hours.
