The first method applies a ‘best fit’ to the Correlation Function and the shape of that fit leads to a diffusion coefficient, an average size, and a size distribution. To get from a Correlation Function to the stuff you really care about – data – two analysis methods are used. This is also why DLS is sometimes called photon correlation spectroscopy (PCS). How quickly particles go from high correlation to zero correlation tells you their average size. Graph these correlation values for a range of jumps of different durations and you get a Correlation Function (Figure 2). Most particles will be in totally different spots – and you now have zero correlation in the data between your starting point and your jump one second later. Now instead of a microsecond, jump forward a full second. In other words, they have a high correlation. Odds are good most particles haven’t moved around yet – so the light scattering hasn’t changed and the data from time zero and a microsecond later are about the same. Here’s how to think about analyzing light scattering data for DLS: pick a point in time – now jump forward a microsecond. Analyzing whether light intensity is changing fast or slow – that’s the secret sauce of DLS. Vice versa for larger ones because they are slower to move around. Since small particles zip around quickly, the intensity of light changes quickly. When the laser wavelength is much larger than the particles, you get equal amounts of light scattering in every direction – that’s why we use a 660 nm laser in our DLS systems.ĭLS can tell you a lot about the size of the particles in solution by measuring how rapidly that scattered light changes over time (Figure 1). This article is written for graduate and undergraduate students with access to DLS and for faculty members who. Shine a laser on a solution of particles and you’ll get plenty of light scattering back out at you. Dynamic light scattering (DLS) analyses are routinely used in biology laboratories to detect aggregates in macromolecular solutions, to determine the size of proteins, nucleic acids, and complexes or to monitor the binding of ligands. Monoclonal antibodies & recombinant proteins.Ultrafiltration & Diafiltration (UF/DF).Differential Scanning Fluorimetry (DSF).The unrivaled particle characterization and ID platform Hound – The unrivaled particle characterization and ID platform.The all-around configurable benchtop workflow solution Junior – The all-around configurable benchtop workflow solution.The only completely hands-free benchtop buffer exchange solution Unagi – The only completely hands-free benchtop buffer exchange solution.The first all-in-one biologics stability screening platform Uncle – The first all-in-one biologics stability screening platform.Honeybun – The most rapid viscometer out there.The one of a kind silicone thickness and distribution analyzer Bouncer – The one of a kind silicone thickness and distribution analyzer.The most customizable automated workflow solution Big Kahuna – The most customizable automated workflow solution.The ultimate automated buffer exchange solution Big Tuna – The ultimate automated buffer exchange solution.The next-gen protein and nucleic acid quantification system Lunatic – The next-gen protein and nucleic acid quantification system.Stunner – The ultimate gene therapy tool.hard sphere, globular, dendrimer, chain stiffness, and degree of branching). Hydrodynamic sizes are more easily measured than radii of gyration and can be measured over a wider range of sizes. The conversion from hydrodynamic radius to radius of gyration is a function of chain architecture (including questions of random coil vs. The hydrodynamic radius is not the same as the radius of gyration. Radius calculations are the same except for a factor of two.Īlso, a note to those interested in polymer size. That is, the determined particle size is the size of a sphere that diffuses the way as your particle.įor those who work with protein sizing and other areas where hydrodynamic radius is more commonly used, note that the development here is around diameter. Finally, and most importantly, it reminds the analyst that the particle size determined by dynamic light scattering is the hydrodynamic size. Temperature is even more important due to the viscosity term since viscosity is a stiff function of temperature. The first is that sample temperature is important, at it appears directly in the equation. However, the equation does serve as important reminder about a few points. The calculations are handled by instrument software. T is thermodynamic temperature (we control this).k B is Boltzmann’s constant (we know this).D t is the translational diffusion coefficient (we find this by dynamic light scattering).D h is the hydrodynamic diameter (this is the goal: particle size!).
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