FIGURE 4.

Recombinant human Hsp72^bv expressed in Sf9 insect cells is endotoxin-free. Recombinant human Hsp72^bv protein was expressed by BEVS in Sf9 cells. Purified protein was examined for endotoxin contamination using a Limulus amebocyte lysate QCL-1000 kit (Cambrex). Briefly, the determination includes a blank for endotoxin standards in quadruplicate. Blank wells contained 50 μl of Limulus amebocyte lysate reagent water instead of the sample. Absorbance was measured at 405–410 nm. Data are the standard curve using the formula: y = 18.923x + 0.2472 (top panel). The mean absorbance (405–410 nm) and corresponding concentrations of the four standards (endotoxin) ranging from 0.01 to 0.1 ng/ml and recombinant human Hsp72^bv protein (bottom panel).