[Heat induced structural transformations in Escherichia coli membranes in the presence of Ca2+]

Using an uncharged hydrophobic fluorescent probe 4-dimethylaminochalkon (DMC) the thermotropic behaviour of cytoplasmic E. coli membranes in the presence of Ca2+ cations was investigated. DMC appeared to be very sensitive in detection of temperature induced phase transitions in E. coli membrane preparations. It was found unexpectedly that Ca2+ does not increased the phase transition temperature of membrane preparations, compared to the values calculated for the membranes in tris-HC1-buffer. The obtained results are briefly discussed.