Sodium butyrate

For recombinant proteins expression, HEK 293F cells were cultured at an orbital shaker incubator in two 1 L flasks containing 500 mL culture volume until the cell density reached 2 x 10 6 cells/mL, and the cell survival rate was above 95%, then infected with recombinant or wild-type baculoviruses (rB or wB) at a multiplicity of infection (MOI) of 20 and incubated at 37 . After 8 h, sodium butyrate (Shanghai Macklin Biochemical Co., Ltd, China) was added to the final concentration of 10 mM, and incubated for 3 days at 37 in 5% CO 2 . Cells were then collected, lysed in 1% Triton X-100, and then centrifuged at 12000 x g for 30 min at 4 . The supernatants were prepared and examined with Western Blot as described below.
The resulting precipitates were resuspended in 1 x phosphate buffer saline (PBS) (pH = 7.4), ultrasonicated, and then centrifuged at 12000 xg for 10 min at 4 . The supernatants were collected and purified using protein G REsin (GenScript, Nanjing, China) according to the manufacturer's instructions. The purified proteins were analyzed using Coomassie Blue stained SDS-PAGE electrophoretogram, then quantified by NanoDrop spectrophotometry (IMPLEN, Germany) and supplemented with 1% protease inhibitor cocktail C (Beijing Yataihengxin Company, China) and frozen at -80 degC until use.