![theory of dynamic light scattering theory of dynamic light scattering](https://www.wyatt.com/wp-content/uploads/2020/08/DynaPro-Plate-Reader-750.jpg)
Light scattering is a technique that can be applied in either batch or chromatography mode. QELS measurements can determine the hydrodynamic radius of macromolecules or particles. * Quasi-elastic (QELS) or dynamic light scattering (DLS): In a QELS measurement, time-dependent fluctuations in the scattered light signal are measured using a fast photon counter. For certain classes of particles, classical light scattering can yield the size, shape, and structure. For the case of macromolecules, this is often called Rayleigh scattering and can yield the molar mass, rms radius, and second virial coefficient (A2). * Classical light scattering: Here, the intensity of the scattered light is measured as a function of angle. Wyatt Technology instruments make two different types of light scattering measurements for absolute molecular characterization: In this sense it is an absolute technique. In contrast to most methods for characterization, it does not require outside calibration standards. Light scattering is a non-invasive technique for characterizing macromolecules and a wide range of particles in solution.
#Theory of dynamic light scattering full#
doi:10.1002/ Core Facility has a full set of Light Scattering equipment from Wyatt including Multiangle Light Scattering (MALS) device, Dynamic Light Scattering (DLS) device, and HPLC system (Agilent) linked to MALS. Hawe, Particles in therapeutic protein formulations, Part 1: overview of analytical methods., J. Berkowitz, eds., Biophysical Characterization of Proteins in Developing Biopharmaceuticals, 1st ed., Newnes, 2014 Need more information? Follow the links below and contact our experts with your questions today.ĭ.J. The kd can be used to predict the colloidal stability of a protein, which may impact the aggregation propensity of a protein within a formulation. Another quantity that DLS can deliver is the interaction parameter (kd) derived from the determination of the diffusion coefficient, which can be a surrogate for the second virial coefficient (B22). For aggregated protein samples, DLS results can show that the aggregate distribution in the sample is polydisperse, but it is not feasible to obtain detailed quantitative information on monomer and aggregate content.ĭLS is mainly used as a research tool during formulation development and to generate supportive data on formulation purity (mainly with respect to aggregate and particle content) for comparability exercises or stability studies.īecause of its high sensitivity to detect minute amounts of aggregates and the possibility to measure small sample volumes (e.g., using plate readers), DLS is a suitable technique for (formulation) screening purposes. Particle concentrations cannot be obtained by DLS. For protein monomers and aggregates, a size range from about 1 nm to several µm can be covered. The particle size range of DLS depends on the properties of the analyzed species, such as refractive index or density, as well as the surrounding formulation, mainly the viscosity. The technique can also be employed for the analysis of colloidal systems, such as liposomes, nanoparticles, polymers and virus-like particles.
![theory of dynamic light scattering theory of dynamic light scattering](https://image.slideserve.com/1409359/slide2-l.jpg)
DLS can determine the hydrodynamic size of protein monomers, small aggregates in the nanometer range and partially also particles in the high nanometer/low micrometer range. Based on intensity fluctuations of laser light scattered by the molecules/particles, moving in Brownian motion, the diffusion coefficient is determined and converted to particle size via the Stokes-Einstein equation.