Method parameters are summarized in Table . The crossflow was maintained at 2.0 mL min -1 for the first 31 minutes of each run (including the focus and transition periods); afterward, it was set to decay linearly over 2 minutes to 0.1 mL min -1 . The crossflow was then maintained at 0.1 mL min -1 for 10 minutes; afterward it was set to zero for the rinse step (the final 10 minutes of the run). The deviation of the FFF channel thickness from its nominal value of 500 µm was estimated using a method described elsewhere, using ferritin and bovine serum albumin as globular protein standards with diffusion coefficients drawn from literature. The FFF method for the globular protein runs is summarized in Table .