Keisuke YOSHIKI, Hiroki AZUMA, Kazuhiko YOSHIOKA, Mamoru HASHIMOTO^* and Tsutomu ARAKI

Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan

(Received November 17, 2004; Accepted June 27, 2005; Revised June 3, 2005)

We have investigated the fluorescence lifetime properties of 8 calcium ion probes, calcium-green-1, calcium green-2, calcium green-5N, calcium orange, oregon green 488 BAPTA-6F, fluo-3, fluo-4, and fluo-5N. We found that the decay time of calcium green-5N varied more sensitively with calcium concentration than calcium green-1 which was known to be a highly sensitive probe. We have also found that the center of observable range of calcium concentration by fluorescence lifetime measurement is lower than that by fluorescence intensity measurement.

Key words: fluorescence lifetime, calcium concentration, calcium green-1, oregon green 488 BAPTA-6F, calcium green-5N, fluo-3, fluo-4, fluo-5N

^*Corresponding author.