What is an AM ester?

The acronym 'AM' represents an acetoxymethyl group, and AM esters are primarily used for the modification of negatively charged carboxylate compounds. By their nature, negatively charged compounds are cell-impermeant and require invasive loading techniques. AM ester modification masks the negatively charged carboxylic groups and produces uncharged hydrophobic indicators or chelators. The resulting cell-permeable AM derivatives can be passively loaded into live cells for analysis. Once inside the cell, nonspecific intracellular esterases, hydrolyze (cleave) the AM groups. Removal of the AM groups results in strongly fluorescent indicators or chelators that are well-retained within the cytoplasm.

Uses of AM derivatives include cell proliferation assays, cell viability and cytotoxicity, measurement of intracellular communication (e.g. calcium signaling), oxidative activity, intracellular pH, and visualization of cellular structures, among others. AM derivatives, after hydrolysis, are fluorescent and should be used with a fluorescence microplate reader, fluorescence microscope, or flow cytometer.

Table 1. Types of AM Derivatives.