AN EFFICIENT AND POSSIBLY GENERAL PACKING MODE FOR CRYSTALS OF B-DNA OLIGONUCLEOTIDES

Two crystal forms of the self-complementary deoxytetramer GpGpCpC have been obtained by use of the phase diagram technique: hexagonal P6(2)22 or P6(4)22 with a = b = 67.7 angstrom, c = 105.6 angstrom, and trigonal P3(2)12 or P3(1)2 with a = b = 116.9 angstrom, c = 116.4 angstrom. Diffraction patterns from both crystals show strong 3.38 angstrom reflections that are typical of base-stacking in B-DNA. The self-rotation function R(phi, psi, 180-degrees) for the hexagonal form exhibits peaks representing pseudodyad rotation, whose periodicity also suggests B-DNA. Crystal packing arguments also favor use of this crystal form for a B helix.