DNA polymorphism in crystals: three stable conformations for the decadeoxynucleotide d(GCATGCATGC).

High-resolution structures of DNA fragments determined using X-ray crystallography or NMR have provided descriptions of a veritable alphabet of conformations. They have also shown that DNA is a flexible molecule, with some sequences capable of adopting two different structures. Here, the first example is presented of a DNA fragment that can assume three different and distinct conformations in crystals.