ImaGene Green™ lacZ Gene Expression Kit contains a A galactosidase substrate of luciferin that has been covalently modified to contain the 12-carbon lipophilic moiety C₁₂FDG. Once inside the cell, the substrate is cleaved by β-galactosidase, producing a fluorescent product that is likely to remain intact within the cell by binding to the lipophilic tail on the cell membrane. In addition to C₁₂FDG, the kit also includes the broad-spectrum β-galactosidase inhibitor PETG and chloroquine diphosphate, which inhibit acidic hydrolysis of the substrate.