Solubilization and condensed packaging of nucleic acids in reversed micelles

RNA and DNA can be solubilized without denaturation in isooctane solutions with the help of reverse micelles formed by di(2-ethyl-hexyl) sodium sulfosuccinate and small amounts of water (down to 0.5%, v:v). With respect to aqueous solutions, RNA (mol. weight 20,000–30,000) in the hydrocarbon micellar solutions shows a decreased absorbance in the 260 nm region, accompanied by an increase of ellipticity. This is attributed to a higher conformational rigidity of the guest biopolymer, and most probably to an increase of base pair stacking. While spectra of low molecular weight samples of DNA (ca. 5000 Daltons) show practically no difference with respect to water, the CD spectrum of the 250,000 Daltons sample is dramatically changed and becomes reminiscent of that of the condensed ψ form. The above spectroscopic effects can be continuously modulated by changing the water content of the micellar system. This offers the possibility of using DNA-containing reverse micelles as models for condensed packaging of DNA in vivo (as in certain phage heads or chromatin).