Dual-Color Imaging of Sodium/Calcium Ion Activities with Two-Photon Fluorescent Probes

摘要

Calcium ions act as a ubiquitous second messenger that controls various functions in cells. In mammallian cells, the cytosolic free Ca~(2+) concentration ([Ca~(2+)]_c) is maintained at about 0.1 μm by the coordinated actions of various calcium ion channels and transporters, whereas the extracellular Ca~(2+) concentration is greater than 1 mM. The near-membrane Ca~(2+) concentration ([Ca~(2+)]_m) is much higher than [Ca~(2+)]_c and can reach values of greater than 100 μm upon activation. The domains with high [Ca~(2+)]_m are the key regions that regulate physiological processes, such as exocytosis, ion-channel activities, and sensory transductions.