Western Lightning™ Ultra is a very sensitive chemiluminescence system for detection of horseradish peroxidase (HRP) on membranes, with maximum sensitivity in the low femtogram range. It incorporates a novel enhancer that intensifies a signal generated by peroxidase catalyzed oxidation of luminol. The substrate produces a signal at 425 nm for at least 8 hours, making it ideal for use with a wide variety of CCD imagers as well as Kodak BioMax® Light or X-OMAT Blue film. Membranes may be stripped and re-probed for detection of multiple targets.