Fig. (4) Effect of NPBD (µg/mL) on cell-free synthesis of β-galactosidase by measurement of ONP (A420nm) ±SD. The relative rate of protein synthesis (slope of the curve with NPBD / slope of the reaction curve at the maximum rate of protein synthesis without NPBD) was the same for all concentrations of NPBD (average 0.98, ±0.01).