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Light Scattering

Light Scattering (LS)

     Classical (static) light scattering, by measuring the intensity of scattered light as a function of angle, provides a method of obtaining the weight average molar mass (Mw),rms radius (Rg) and second virial coefficientIE. The light intensity carries information about the molar mass and the angular dependence about the molecular size. The intensity of the scattered light despends on the magnitude of the induced dipole of the macromolecule and dn/dc allows the oberved scattering to be related to molar mass. Multiangle static light scattering is a powerful tool when combined with SEC and an online refractive index detection allows absolute mass determination without the need for standards. This is particularly desirable for highly glycosylated proteins that have shapes that can be significantly different from typical globular standards. Dynamic light scattering (quasi-elastic, QELS) is different in that it measures the time-dependent fluctuations in the intensity. From the diffusion coefficient, the hydrodynamic radius (Rh) can be calculated with the Stokes-Einstein relation. While large, globular molecules can generlly be measured just at 90°, rod shaped molecules need angular extrapolation to eliminate rotational diffusion contributions to Rh.

Applications

  1. Detection of protein aggregates in solution (eg. stored formulations, reconstituted powders) REF

Pros:

Cons:

  1. Not very sensitive to smaller molecules
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