A new method for calibrating micropipets and determining accurate inje
ction volumes using a pressure-based injector has been developed. This
method employs the bioluminescent protein aequorin and can be used to
determine injection volumes as small as 3 pt. The calibration plots a
re linear over at least 3 orders of magnitude. In contrast to conventi
onal micropipet calibration methods that employ fluorescent molecules,
the present method produces small background signals.