It is possible to precipitate but resolubilize in 2D lyis or rehydration buffer is very very difficult. When you add buffer, your pellet becomes transparent so mix with pippete and you will know that it is not dissolved completely.
TCA/acetone precipitation for 2-DE is normally used only for more hydrophobic and membrane proteins. For all other proteins acetone precipitation or dialysis as Fatemen above already indicated is more suitable. If you still need TCA/acetone precipitation you should precipitate the pellet after that in 80% cold acetone to remove the TCA which disturbs the IEF. After the acetone precipitation be careful with drying the pellet since if it becomes too dry it is difficult to resolubilize. If you still see crystals (=urea/thiourea) instead of the normally white-brown protein pellet after this drying then wash the protein pellet several times in ethanol to further clean the pellet.
Thanks a lot..for your help..Fatemeh Barantalab ,Steffen Ohlmeier and Narendra Sharma for your kind suggestions..CAN you please let me know can we make 2d sample only for membrane proteins without using ultracentifuge.
An ultracentrifuge is normally not required for the preparation of membrane protein extracts for 2-DE since already a normal centrifuge speed allows the separation into soluble and insoluble fraction.
Yes, membrane proteins are quite tricky and difficult to solubilize or to get into the gel. If you tried already different detergents (e.g. CHAPS, SB3-10, ASB12,...) also at higher concentrations and different commercial membrane enrichment kits as well as sample cup loading for IEF then it might be better to enrich the membrane proteins as much as possible and use 1DE for this analysis since here you can use SDS....or you use straight MS.
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