In vivo bioluminescence imaging (BLI) is limited by the fact that the luminescence signal from native D-Luciferin (maximum emission at about 560 nm) is attenuated in the animal due to absorption and scattering of light below 600 nm in blood and tissues. These shortcomings can be avoided using a red-shifted luciferin derivative (max. em. at 600 nm) like CybLuc. In addition to red shift properties, CybLuc also displays higher lipophilicity and metabolic stability. This make it the ideal luciferin for in vivo studies. Biosynth is the only supplier of commercial CybLuc.