Brightness measurements are integrated over time, so when comparing them make sure they are integrated over a long time (otherwise you are only measuring how quickly luminescence occurs, not how bright).
Different colours:
Could use fluorophores instead of fluorescent proteins but need to ensure they attach to protein (could be a project in itself). Requires resonance energy transfer.
Using mutant luciferases probably easier to implement.
Expression in E. coli: inclusion bodies could be a problem when trying to over-express genes. To test: break open cells and centrifuge twice (at a higher speed second time around), if pellets are formed these are probably inclusion bodies. Could then dissolve these with solvent and test for bioluminescence from proteins within inclusion bodies.
Relative light units are used because different camera properties, distances etc. all mean that photons/sec are relative. Can use a source for calibration - tritium standards are used (e.g. MGM instruments).
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