Nucleic Acids Research: VOLUME 39 ISSUE 8 2011

dG-dC) .(dG-dC) was converted to the Z conformer by heating in the presence of HH + . Reaction of this preparation with the crosslinking reagent, DL-diepoxybutane (DEB), stabilized this conformer so that it retained Its structure even when returned to conditions that favored reversion to the B conformation. Treatment of the crosslinked Z conformer with perlodate caused scission of the crosslink, allowing reversion to the B conformer. Reaction of (dG-dC) .(dG-dC) in the B conformation with DEB did not prevent conversion to the Z eonformer in MM NaCl; dialysis of the high salt solution against low ionic strength buffer allowed return to the B conformer. The Zp£ B transitions were followed by circular dichroism studies and immunochemical procedures. The results suggest the feasibility of stabilizing Z sequences of DNA In chromatln by orosslinking , so that they could then be identified after DNA isolation.