CCF2-FA (Free Acid) is a fluorescence resonance energy transfer (FRET) substrate that consists of a cephalosporin core linking B7-hydroxycoumarin to fluorescein. This product is intended for use as a beta-lactamase substrate in a GeneBLAzer™ cell-based assay.

GeneBLAzer™ cell-based assays typically utilize the membrane-permeant ester forms (CCF2-AM and CCF4-AM) of the negatively charged fluorescent beta-lactamase substrates, CCF2 and CCF4. These lipophilic esters readily enter the cell, where cleavage by endogeneous cytoplasmic esterases rapidly converts them into their negatively charged forms, thereby trapping them in the cytosol.

CCF2-FA is essentially the CCF2 substrate without the esters found in the AM version. CCF2-FA is de-esterified and used in cell lysate applications, bypassing loading across the cell membrane and de-esterification steps. Cell lysates are the preferred method for applications using cells that contain a cell wall. CCF2-FA can also be used as a control to acquire the excitation and emission spectra for CCF2-AM and CCF4-AM.