Abstract
The ability to modulate the regulatory components controlling the lactose (lac) operon, including the key LacI repressor molecule, presents an opportunity to study the expression of proteins of interest. In particular, isopropyl ß-D-1-thiogalactopyranoside (IPTG) may be applied to systems containing the lac operon to increase the transcriptional activity of genes regulated by elements of the lac operon. This paper presents methods by which IPTG can be used to induce fluorescent protein expression in both plate and broth-based assays. Through the employment of these techniques, fluorescent protein probes may be measured qualitatively and quantitatively to study protein expression levels and transcriptional regulation.