Table 3. Comparison of the GUS-inducing activity of pe/D inducer 2 and homoserine.

Inducer	GUS activity*
pe/D inducer 2†
1.05 mM	2,374
2.62 mM	3,550
5.25 mM	5,887
Homoserine
1.05 mM	2,171
2.62 mM	4,262
5.25 mM	4,862

^*Arbitrary fluorescence units.

^†Concentration of inducer 2 is based on the amino acid content of the inducer 2 preparation as determined by quantitation with ninhydrin (20).