The manipulation of ribosomal RNA(rRNA) extracted from E. coli cells by dielectrophoresis(DEP) has been demonstrated over the range of 3 kHz–50 MHz using interdigitated microelectrodes. Quantitative measurement using total internal reflection fluorescence microscopy of the time dependent collection indicated a positive DEP response characterized by a plateau between 3 kHz and 1 MHz followed by a decrease in response at higher frequencies. Negative DEP was observed above 9 MHz. The positive DEP response below 1 MHz is described by the Clausius–Mossotti model and corresponds to an induced dipole moment of 3300 D with a polarizability of 7.8×10−32 F m2. The negative DEP response above 9 MHz indicates that the rRNA molecules exhibit a net moment of −250 D, to give an effective permittivity value of 78.5 ε0, close to that of the aqueous suspending medium, and a relatively small surface conductance value of ∼0.1 nS. This suggests that our rRNA samples have a fairly open structure accessible to the surrounding water molecules, with counterions strongly bound to the charged phosphate groups in the rRNA backbone. These results are the first demonstration of DEP for fast capture and release of rRNA units, opening new opportunities for rRNA-based biosensing devices.
- biological electrophoresis
- fluorescence microscopy