Just some quick thoughts about the attached excel on my previous post…
The 100K nanosep does not have a hydraulic permeability value at 194.65psi because it passed all 500uL of water through in 1minute which is the smallest interval of time a test can be run at with the new centrifuge. When I get a minute I will run this test using the smaller centrifuge using shorter time increments.
For the bar graph the x axis is in terms of pressure, the first set is of bars is at 1.35psi, the second set is 8.45psi, the third 21.63psi, the fourth 33.79psi, and the fifth is 194.65psi.
For the 100K nanosep, how high would the bar be if it just passed the 500 uL at the one minute mark? Is it very close to the others or 2X higher? Have we done any separations to confirm that there is not breach in any of these membranes? I’m very curious to see how our material compares in terms of separation efficiency.
—Chris
Chris –
I have performed a few experiments on Cytochrome C (12kD) pass-thru and retention by the 100k and 50k Micrcons @ 10k rpm. I’ll formalize the data once I also test them against BSA or HSA.
Not surprisingly, the 100k Microcon passed ~100% of Cytochrome C (both 0.5 and 1.0 mg/mL conc) meaning nothing was lost or retained. With the 50k Microcon, the filtrate concentration was ~0.25mg/mL for a 0.5 experiment and ~0.3mg/mL for the 1.0. There was significant retention/concentration of CytoC in the retentate even though the cutoff was claimed at 50k (or 4x higher than cytoC). I was surprised at the dramatic difference between the 50k and 100k membranes with such a small molecule. This likely gives us a very large window to fit in. The Microcon instructions suggest that you should use a cutoff 3-6x smaller than the molecule retained.
For example – if you wanted to retain and concentrate a 150kD or 300kD protein, you would use a 50kD filter, but you if you had 12kD contaminants like CytoC, you would find them in your retentate along with your 150kD or 300kD protein of interest. Jess’ experiments thus far suggest we should be able to do much better.
-Tom