Calcein

Calcein

Chemical structure of Calcein

Calcein is a fluorescent dye commonly used in biological research and imaging techniques. It belongs to the family of xanthene dyes and is known for its strong green fluorescence when excited by blue light. Calcein is widely used in various applications, including cell viability assays, calcium imaging, and pH measurements.

History

Calcein was first synthesized in the early 20th century by Adolf von Baeyer and his colleagues. Its name is derived from the Latin word "calx," meaning lime or limestone, due to its ability to form complexes with metal ions. Initially, calcein was primarily used as a pH indicator and for studying metal ion complexation. However, its fluorescent properties soon gained attention in the field of biological research.

Chemical Properties

Calcein has a molecular formula of C_30H_26N_2O_13 and a molecular weight of 622.53 g/mol. It consists of three main functional groups: two carboxylic acid groups and one xanthene ring. The xanthene ring is responsible for its fluorescent properties, while the carboxylic acid groups allow for easy conjugation with other molecules.

Applications

Cell Viability Assays

One of the most common applications of calcein is in cell viability assays. Calcein-AM, a cell-permeable derivative of calcein, is used to assess the viability and metabolic activity of cells. When calcein-AM enters live cells, it is cleaved by intracellular esterases, resulting in the formation of calcein, which emits green fluorescence. The intensity of the fluorescence is directly proportional to the number of viable cells.

Calcium Imaging

Calcein is also widely used for calcium imaging, a technique used to monitor changes in intracellular calcium levels. Calcein can form complexes with calcium ions, resulting in a shift in its fluorescence emission spectrum. By monitoring the changes in fluorescence intensity, researchers can study calcium dynamics in various biological processes, such as neuronal signaling and muscle contraction.

pH Measurements

Due to its pH-sensitive properties, calcein is often employed as a pH indicator in biological systems. The fluorescence emission of calcein is highly dependent on the pH of the surrounding environment. This property allows researchers to monitor pH changes in cellular compartments, such as lysosomes and endosomes, providing valuable insights into cellular processes and organelle function.

See Also

• Fluorescent dye
• Xanthene dyes
• Cell viability assay
• Calcium imaging
• pH indicator