hi all,
i am trying to concentrate some mammary proteins isolated using Trireagent for Western analysis. i have been using 3kDa Centricons from Millipore, which would normally work fine except for one hinderance - my concentration of SDS. My isolated samples are in 0.1M Tris-1%SDS, which (if my calculations are correct) is equivalent to 34.7mM SDS. The CMC of SDS is 8.3mM and the MW of an SDS micelle is 18kDa. Therefore not only would I be concentrating my protein, but also the SDS. To remedy this (so I thought), I diluted my protein samples 1:10 so that the SDS concentration would be less than the CMC. Long story short, I started with 1mL of diluted protein sample in the Centricon and I am now down to ~35uL, but the concentration is only just above my original (pre-dilution of 1:10) concentration, and still not enough to run a reasonable volume on a SDS-PAGE gel!

Is it feasible to just concentrate my undiluted protein isolates and not worry about my final concentration of SDS for WB?

Any suggestions would be greatly appreciated

I use 25% PEG8000 to concentrate my protein. briefly, add 1:1 Vol of 25% PEG8000 to the protein extract, RT 30min, 18000g or higher spin down.
I use this to concentrate my coprecipatated proteins, hope it will work for you.