Case12 is a high dynamic range genetically encoded fluorescent sensor for direct measurement of changes of intracellular Ca²⁺ under various physiological and pathological conditions [Souslova et al., 2007]. The sensor is sensitive to changes of calcium concentration in a physiological range from a hundred nanomoles to micromoles with a high signal-to-noise ratio. Binding of Ca²⁺ is fast and reversible, allowing monitoring of high-frequency Ca²⁺ oscillations. In response to Ca²⁺ concentration rise, Case12 shows up to 12-fold increase of fluorescence brightness. Fluorescence of Case12 is characterized by single excitation/emission maxima peaked at 491/516 nm.

Case12 is recommended for monitoring change of calcium concentration inside living cells during various physiological and pathological conditions.