Lifetime-based fluorescence energy transfer biosensing of zinc

A new type of fluorescence transduction method for determining zinc in solution is described. The approach is based upon energy transfer from a fluorescent label on an enzyme, human carbonic anhydrase II, to a colored inhibitor which binds to zinc in the enzyme active site. If zinc is present in solution, it binds to the apoenzyme, which in turn permits the inhibitor to bind to the enzyme; the inhibitor is thus in close proximity to the label on the enzyme and thereby quenches the label's fluorescence by Forster energy transfer with a concomitant reduction of its lifetime, which is quantitated by phase fluorometry.