The solution structure of a DNA dodecamer is determined by combining dipolar cross-relaxation and residual dipolar coupling (RDCs) data. The C-13-H-1 RDCs result from the partial alignment of the molecule after its dissolution in different oriented dilute liquid crystals: polyethylene glycols, bicelles and phages. It clearly appears that thanks to the use of RDCs, the global curvature of the duplex solution structures is reduced. This is shown to result from the use of long-range RDC restraints and from the symmetry properties of a self-complementary dodecamer. (C) 2004 Academie des sciences. Published by Elsevier SAS. All rights reserved.