DNA fractionation by two-phase partition with aid of a base-specific macroligand

The application of a GC (guanosine-cytidine)-specific DNA macroligand, consisting of a GC-specific phenazinium dye covalently bound to one end of polyethylene glycol (6000–7500 $\text{M}{}_{\mathrm{r}}\text{)}$, for preparative DNA fractionation with base composition is described. The fractionation is performed in aqueous two-phase systems formed by polyethylene glycol and dextran in which the macroligand shows a strong affinity for the upper phase and shifts the partition coefficient of the DNA as a function of its GC content. Examples of fractionations by simple extractions and countercurrent distributions of calf thymus DNA over a few steps are given.