Nonrad. ATP synthase assays?

[CConley]

Hello --
      I'm trying to characterize the activity of ATP synthase from isolated
mitochondria. I'd like to use a non-radioactive assay -- I've heard of a
luciferase assay, where one adds luciferase, substrates, and ADP to the
mitochondria and then measures the fluorescence.  Is this a good assay,
what might be problems with it, and are there other assays which I should
consider (commercial products)?
      Thanks,
                                               -- CConley