Development and in vitro characterization of ratiometric and intensity-based fluorescent ion sensors.

Fluorescent ion sensors are quite valuable in experimental biology. The development of new sensor molecules requires determination of spectral properties (absorption bands, fluorescence excitation, and emission maxima) in order to characterize the type of optical response to the target ion. This optical response type and magnitude are used, in combination with solutions of buffered ion of precisely manipulated concentration, to determine the in vitro affinity for the target ion. Buffered aqueous ion solutions of appropriate pH and ionic strength are necessary to predict the performance of new sensors in biological applications. A series of novel benzoxazole-BAPTA calcium sensors, in addition to Rhod-3 (a new version of rhod-2), are described and their optical responses to calcium ion characterized.