First of all, isn't the choice either dimer or trimer, and second, as a protein-detergent complex (PDC), it would be very unlikely that a trimer of 99 kD would run at 100 kD, although all is fair in love, war, and membrane proteins.
JPK On Thu, Jun 21, 2012 at 10:50 AM, Raji Edayathumangalam <r...@brandeis.edu>wrote: > Hi Everyone, > > Sorry for the non-CCP4 post. > > I have a very basic question about detergents, critical micelle > concentration and behavior on gel filtration. > > A 33kDa membrane protein was purified by gel filtration in a buffer > containing 0.4%(w/v) beta-NG (CMC: 6.5mM) and 0.046%(w/v)LDAO (CMC: > 0.14mM). So the concentrations of beta-NG and LDAO in the gel-filtration > buffer are ~2X and ~14X that of the CMCs of the respective detergents. The > elution volume of the protein peak (plus detergent) on Superdex200 > corresponds to a molecular mass of 100kDa. > > I think that the 100kDa mass above includes contributions from both the > protein as well as the detergent micelles. If this is correct, is it then > accurate to try to glean the oligomerization state of the protein (and > conclude that it is a trimer or tetramer) without taking into account > detergent micellar mass and its influence on elution volume? > > How should one interpret the 100kDa mass estimate from the gel filtration? > > Thanks. > Raji > > > > > > -- > Raji Edayathumangalam > Instructor in Neurology, Harvard Medical School > Research Associate, Brigham and Women's Hospital > Visiting Research Scholar, Brandeis University > > > -- ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program email: j-kell...@northwestern.edu *******************************************
