Static Light Scattering
Measure particle properties like protein aggregation and empty/full capsid ratio
Learn more with light
Static Light Scattering (SLS) might seem simple at first — a laser goes into a sample, hits particles, and bounces back out — but SLS is actually one of the most powerful techniques to detect particles in solution. The intensity of reflected light is the main readout of an SLS experiment and, if you know what you expect of your sample, that intensity can tell you a lot. SLS can be used to calculate titers of viral particles, or as the most sensitive way to keep an eye on when aggregation begins in a sample.
SLS is able to do all this through the power of light.
How does SLS work?
With SLS, laser light is directed at your sample and the scattered light is measured at one or more angles around the sample. Because the intensity of scattered light can be affected by a number of properties of your sample and setup, such as:
- Particle molecular weight
- Particle size (Rg)
- Particle concentration
- Interactive forces between particles
- Refractive indices of the particle and solvent
- Angle between the laser and detector
- Laser wavelength
We can use the measured intensity to characterize the particles in your sample. Here’s how it works:
Shine the right light
Particles that are small relative to the light wavelength will scatter light evenly in all directions (Rayleigh scattering). For UV and visible lasers, biologics like proteins and AAV are considered small.
The intensity of the scattered light will depend on a number of factors related to your sample, your light source, and your detection setup. For small, dilute particles, intensity is proportional to:
- Particle molecular weight (M)
- Particle concentration (C)
- Refractive index of the buffer (no)
- Differential refractive index of the particle relative to concentration (dn/dc)2
Turn up the heat
With SLS and a thermal ramp, you can measure the aggregation temperature (Tagg)—that’s the temperature when SLS intensity begins to increase and aggregation gets out of hand.
…or get a two-for-one
With simultaneous SLS and DLS, you can figure out just the intensity coming from AAV capsids. That’s the first step to getting easy and quick AAV titers.
SLS vs DLS—What’s the difference?
Ready for more?
Biopharma scientists can now use the right tool for protein aggregation and capsid characterization with instruments that combine SLS with DLS, fluorescence, and UV/Vis. Have a question or ready to find out more?