Hi Wei, this milk is precipitated/microcrystals of SDS probably with some phosphate since you are in PBS buffer. I would have two suggestions. 1-Can't you find a better detergent than SDS for your membrane protein? Have you run a detergent screen for this protein to find a milder and more crystallization friendly detergent for the reconstiution/purification and handling of your sample. SDS is very very rarely used for membrane protein crystallization. 2- I would try to avoid preparing a protein for crystallization in a phosphate containing buffer (unless you have no choice). Phosphates tend to yield more salt crystals at the screening stage.
Hope this helps. > -- Pascal F. Egea, PhD Assistant Professor UCLA, David Geffen School of Medicine Department of Biological Chemistry 356 Boyer Hall office (310)-983-3515 lab (310)-983-3516 email pe...@mednet.ucla.edu
