Fluorescent probe study of DNA conformation in briefly heated human squamous cells: brief communication.

To determine whether temperature levels commonly encountered in hot beverages denatured the DNA of intact human squamous cells, a fluorescent probe and model system with trypsin-treated desquamated buccal cells were employed. The probe statistically distinguished between single- and double-stranded DNA in a population of suspended cells by the differential bond strengths of DNA-acriflavine complexes over a 4--25 degrees C temperature gradient. The fluorescence of complexed dye was quenched and that of freed dye was restored, which simplified analysis. After cell pellets were admixed with small volumes of suspension medium preheated to 70 or 80 degrees C for 6 seconds, quickly cooled, and stained with acriflavine under conditions favoring the intercalative mode of binding, a temperature-dependent increase occurred in the fraction of complexed dye that was released over the 4--25 degrees C test range. This increase suggested that brief heating partially denatured the DNA of human buccal squamous cells.