All data are obtained from the means of respectively three independent measurements.
|Exposure duration||continuous for 45 minutes|
|Setup||exposure system consisted of a 17 cm x 17 cm square aluminium waveguide with a length of 60 cm; waveguide was split in its center in two equal parts to provide access to the X-shaped sample holder; two fans at two sides of the waveguide circulated the air and kept the temperature approximately constant in the incubator (37°C); the DNA sample in a polystyrene tube (with 5 cm in length and 1 cm in diameter) was fixed horizontally inside the X-shape holder and placed inside the waveguide|
|Additional info||control sample was placed in a small shielded box and placed outside the waveguide structure, but in an incubator to have the same temperature treatment|
The UV-vis and circular dichroism experiments showed that the exposure caused disturbances on the structure of DNA (absorbance in the UV-vis spectrum was incremented and a shift in the maximum of the circular dichroism spectrum, as well as a decrease of the molar ellipticity in exposed DNA). In addition the exposed DNA samples were thermally more unstable than unexposed DNA (melting point decreased in exposed samples). Furthermore, the exposed DNA samples showed an increased fluorescence emission compared to the unexposed DNA samples, which may have occurred attributable to expansion of the exposed DNA (increased fluorescence intensity in exposed DNA incubated with berberine). The results of dynamic light scattering and zeta potential experiments demonstrated that the surface charge and the size of DNA was incremented in exposed samples compared to unexposed ones (hydrodynamic radius and zeta potential increased in exposed samples). The structure of the DNA examined immediately after the exposure is not significantly different from the DNA examined 2 h after the exposure.
Collectively, these experiments indicate that exposure to an electromagnetic radiofrequency field can alter the structure of DNA irreversibly.