I need a control of beta amyloid monomers but I am using FCS and will be determining the size through the diffusion coefficient of the fluorescently labeled proteins.  Therefore the monomers need to be able to diffuse unhindered.  If the SDS binds to the monomer and slows its diffusion, it may throw off the diffusion coefficients determined for the larger aggregates in my experiment.

Also, this is being done in a 3D hydrogel so there will be more limited diffusion than in a solution.