text: Luciferases can be produced in the lab through genetic engineering for a number of purposes.  Luciferase genes can be synthesized and inserted into organisms or transfected into cells. As of 2002, mice, silkworms, and potatoes are just a few of the organisms that have already been engineered to produce the protein.
  In the luciferase reaction, light is emitted when luciferase acts on the appropriate luciferin substrate. Photon emission can be detected by light sensitive apparatus such as a luminometer or an optical microscope with a CCD camera. This allows observation of biological processes.  Since light excitation is not needed for luciferase bioluminescence, there is minimal autofluorescence and therefore the bioluminescent signal is virtually background-free.  Therefore, as little as 0.02 pg can still be accurately measured using a standard scintillation counter.
  In biological research, luciferase is commonly used as a reporter to assess the transcriptional activity in cells that are transfected with a genetic construct containing the luciferase gene under the control of a promoter of interest. Additionally, proluminescent molecules that are converted to luciferin upon activity of a particular enzyme can be used to detect enzyme activity in coupled or two-step luciferase assays. Such substrates have been used to detect caspase activity and cytochrome P450 activity, among others.
  Luciferase can also be used to detect the level of cellular ATP in cell viability assays or for kinase activity assays. Luciferase can act as an ATP sensor protein through biotinylation. Biotinylation will immobilize luciferase on the cell-surface by binding to a streptavidin-biotin complex. This allows luciferase to detect the efflux of ATP from the cell and will effectively display the real-time release of ATP through bioluminescence. Luciferase can additionally be made more sensitive for ATP detection by increasing the luminescence intensity by changing certain amino acid residues in the sequence of the protein.
  Whole organism imaging (referred to as in vivo when intact or, otherwise called ex vivo imaging for example of living but explanted tissue) is a powerful technique for studying cell populations in live plants or animals, such as mice. Different types of cells (e.g. bone marrow stem cells, T-cells) can be engineered to express a luciferase allowing their non-invasive visualization inside a live animal using a sensitive charge-couple device camera (CCD camera).This technique has been used to follow tumorigenesis and response of tumors to treatment in animal models. However, environmental factors and therapeutic interferences may cause some discrepancies between tumor burden and bioluminescence intensity in relation to changes in proliferative activity. The intensity of the signal measured by in vivo imaging may depend on various factors, such as -luciferin absorption through the peritoneum, blood flow, cell membrane permeability, availability of co-factors, intracellular pH and transparency of overlying tissue, in addition to the amount of luciferase.
  Luciferase is a heat-sensitive protein that is used in studies on protein denaturation, testing the protective capacities of heat shock proteins. The opportunities for using luciferase continue to expand.