CaEGTA

CaEGTA is the calcium salt of ethylene glycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid, a chelating agent used to regulate free calcium ion (Ca2+) concentrations in biochemical and physiological experiments. In solution, CaEGTA binds Ca2+ to form a stable CaEGTA complex, enabling researchers to control the amount of unbound Ca2+ present. This buffering is essential for studying Ca2+-dependent processes and for maintaining stable Ca2+ levels during experiments such as enzymatic assays, Ca2+ imaging, and electrophysiological recordings.

The CaEGTA buffering system works by balancing total Ca2+ and total EGTA (the ligand) at a given pH. The fraction of Ca2+ that remains free depends on the EGTA-to-Ca2+ ratio and the solution’s pH, with the pH strongly influencing the binding affinity. At physiological pH, CaEGTA provides high affinity for Ca2+ and is commonly used to establish free Ca2+ concentrations ranging from sub-micromolar to low micromolar, suitable for many cellular and molecular studies. The system is generally less effective at buffering Mg2+ compared with Ca2+, which can be relevant when magnesium ions are present in the experiment.

Practical use involves calculating the required amounts of CaEGTA and Ca2+ to achieve a target free Ca2+ concentration, often with software tools such as MaxChelator or similar buffers. The resulting CaEGTA solution is then incorporated into the experimental milieu, typically alongside standard ionic buffers, to ensure stable and reproducible calcium levels under the chosen experimental conditions.