Dimethylaminochalcone, an indicator of structural changes in theE. coli cell membrane produced by Ca++ cations and tris buffer

An attempt was made to find hypothetical structural changes in the cell membrane ofEscherichia coli under the influence of Ca++ cations with the aid of the uncharged fluorescent proble 4-dimethylaminochalcone (DMC). Effects of Tris buffer (0.01 M) at 0°C and of other agents, namely Mg++ cations and EDTA, also were tested for comparison. Treatment of theE. coli cells with Ca++ cations was shown to cause structural changes in the surface of the cell membrane which differed from the changes produced by treatment with Tris buffer at 0°C, Mg++ cations, and EDTA. DMC can be used with success as an indicator of structural changes in biomembranes.