Different forms of the double helix in the pCpGpCpGpCpG crystals.

Four different crystal forms of the self-complementary oligonucleotide pCpGpCpGpCpG have been obtained. The space groups and the unit cell parameters of these crystals, as well as the location of the base-stacking reflections, indicate that the oligonucleotide is able to assume different double helical conformations that are dependent on the crystallization conditions.