Pressure changes the shape of gold sieving curves – and our model agrees with experiment!
The below figure has three different sieving curves. Solid lines are model calculations assuming a SiN membrane with 37 nm pores, and either 0.4, 1.3, or 5 PSI applied to drive the separation. Markers are real data. Note that the experimental data reflects the pressure-dependence of the curve, but is slightly different in concavity from the model. Also interesting is that the effect is MORE pronounced experimentally than it is in the model, in both the less and more pressure cases. 
Does this throw a monkey wrench into the concept of a SepCon device with a sharp cutoff for proteins, since the cutoff would continuously shift as the head pressure drops as the fluid level decreases above the membrane? You guys know better than I do, but it seems like experiments that were done with continuous backing pressure have shown a sharper cutoff than with spin devices, but there are so many factors involved, that may be too much of a generalization. However, this model seems to support the idea that a continuously changing pressure may work against the sharp cutoff that we are often looking for…
Interesting results..thank you!!