TCA precipitation
This protocol was derived from the DOC-TCA protocol previously described [13]. Conditioned medium (20 mL) was first cooled on ice in a high-speed centrifuge tube. Sodium deoxycholate or sodium lauroyl sarcosinate (NLS) was added to a final concentration varying from 0.01 to 0.1%. After mixing, TCA was added to a final 7.5% concentration, and the solution was precipitated on ice for 2 h. The mixed protein-detergent precipitate was collected by centrifugation (10 000 6g, 10 min, 47C). The supernatant was carefully removed, 2 mL of tetrahydrofuran (THF, precooled in ice) were added to the pellet and vortexing was carried out until the pellet unstuck from the bottom of the tube, and dissolved almost completely. Centrifugation was carried out as described above. The supernatant was removed, and the nearly invisible pellet was washed again with 2 mL of THF. Finally, the pellet was redissolved in 0.4 mL extraction solution with the help of a sonicator bath (30 min extraction).
From Chevallet, et al Proteomics 7, 1757-70 (2007)
The classic (Ref 13 above) is "Assay of Proteins in the Presence of Interfering Materials" Anal Biochem 70, 241-50 (1976)
Optimum protein ppt was observed in the presence of 125-250 micrograms/ml of sodium deoxycholate. Temperature was not a major parameter in recovery.