Exploration of triple-helical fragments: crystallization and preliminary X-ray diffraction of d(TGGCCTTAAGG).

The nonamer d(GCGAATTCG) and decamer d(GGCCAATTGG), containing one and two overhanging guanines, respectively, form G x GC triplets in their crystal packing. In order to introduce a third subsequent T x AT triplet, the decamer was further extended by one overhanging thymine residue. Two different crystal morphologies of the sequence d(TGGCCTTAAGG) were obtained by hanging-drop vapour diffusion and diffracted to 2.5 and 2.3 A resolution, respectively. However, both crystals belong to the orthorhombic space group P2(1)2(1)2(1), with similar unit-cell parameters. Therefore, the two data sets could be merged to a resolution of 2.4 A with unit-cell parameters a = 26.97, b = 41.12, c = 52.72 A.