Influence of optical probing with YOYO on the electrophoretic behavior of the DNA molecule.

The influence of the fluorescent dye YOYO (1,1'-(4,4,8,8,-tetramethyl- 4,8-diazaundecamethylene)bis[4-[[3-methyl-benzo-1,3-oxazol-2 -yl] methylidene]-1,4-dihydroquinolinium] tetraiodide) on the electrophoretic behavior of the DNA molecule was investigated. This is important when using YOYO as a probe in capillary electrophoresis or in fluorescence microscopy studies of DNA with the purpose of studying the migration mechanism of DNA on the molecular level. We have measured the mobility and orientation dynamics (using the linear dichroism technique) for both pure DNA and the YOYO-DNA complex in agarose gel in order to compare their electrophoretic properties. Mobility decreases, the degree of orientation becomes lower, and the orientational dynamics slower, when YOYO binds to DNA. However, the dependence on field strength of the mobility, orientation and orientational dynamics, are similar for DNA and YOYO-DNA, indicating that the mode of migration does not change significantly upon binding YOYO to DNA. Furthermore, since our results show that the effect of YOYO on both the degree of orientation and orientational dynamics of the DNA can be measured and therefore be compensated for, it can be concluded that YOYO is an excellent optical probe for the study of the migrational behavior of DNA.