The idea is to measure the hydro- protein sizes in various solvents (eg. with high ionic strength, EtOH/Water, other organic/water solvents), then, due to the extremely low solubility of some organic solvents in water, in some organic solvent/water systems, the final samples are not "clean". It would be a problem, right? Ethanol is miscible with water, then, it is ok?
Appreciate for any comments, thanks.
Best,
Yuhong
Hi Yuhong Mao,
it is right. The solvents shoud be complete dissolved and "clean". Furthermore, for solvent mixtures you have to measure or calculate the viscosity. The viscosity plays an important role for the hydrodynamic radius by the Stokes-Einstein equation. I would recommand you to clean the cuvette and your solvents. Due to large dust particles or other impurities it could be a problem to see you particles. Bigger particles scatters the light much more in the ratio diameter^6. So, a 100 nm scatters the light 1.000.000times more than a 10 nm particles.
More details you will find here:https://www.malvernpanalytical.com/de/learn/knowledge-center/technical-notes/TN101104DynamicLightScatteringIntroduction
Greetings,
Maximilian
Yuhong Mao
If you wish to measure hydrodynamic size of proteins, then you need to disperse and not dissolve the protein in solvent.
Maximilian Muenzner Just as a small side note. For particle size distributions calculated from brownian motion, one has to take into account the viscosity of the medium not the viscosity of the dispersion. Since there should not be any pp interactions for brownian motions anyways.
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