Membranes measurements with 6-carboxyfluorescein

Esterase substrates have long been used as a measure of cell membrane integrity, with the fluorescent product being the marker retained. The one that has been used most often with fish cell lines is 5-carboxyfluorescein diacetate acetoxymethyl ester (CFDA-AM)174 CFDA-AM diffuses into cells rapidly and is converted by... 

Proton flux across lipid bilayers can be measured by a variety of techniques. For example, a buffered pH gradient can be established across liposome membranes, and the rate of decay of the gradient can be monitored by any of several methods. Early measurements were carried out by monitoring pH shifts in the external medium with a glass electrode (1) later measurements used pH-sensitive dyes such as pyranine, carboxyfluorescein, and 9-aminoacridine (4-6). Cafiso and Hubbell (7) used spin labels very effectively, and Perkins and Cafiso (8) conducted an extensive series of measurements with this system. 

Membrane permeabilization activity of peptides is currently measured by the use of artificial membrane bilayers, such as liposomes or erythrocytes. The hposome leakage assay can be performed by using spectrofluorimetry with a concentration-dependent quenching of a dye (calcein, carboxyfluorescein) encapsulated in liposomes. Disruption of hposomes in the presence of peptide-inducing leakage will lead to an increase in the fluorescence intensity of the liposome solution. Erythrocyte lysis assay is based on the absorption of hemoglobin, which can be measured once released into the extracellular medium upon erythrocyte lysis in the presence of peptide. 

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