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Science 23 November 2007:
Vol. 318. no. 5854, pp. 1276 - 1279
DOI: 10.1126/science.1143826
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Reports

End-to-End Stacking and Liquid Crystal Condensation of 6– to 20–Base Pair DNA Duplexes

Michi Nakata,1*{dagger} Giuliano Zanchetta,2* Brandon D. Chapman,3 Christopher D. Jones,1 Julie O. Cross,4 Ronald Pindak,3 Tommaso Bellini,2{ddagger} Noel A. Clark1{ddagger}

Short complementary B-form DNA oligomers, 6 to 20 base pairs in length, are found to exhibit nematic and columnar liquid crystal phases, even though such duplexes lack the shape anisotropy required for liquid crystal ordering. Structural study shows that these phases are produced by the end-to-end adhesion and consequent stacking of the duplex oligomers into polydisperse anisotropic rod-shaped aggregates, which can order into liquid crystals. Upon cooling mixed solutions of short DNA oligomers, in which only a small fraction of the DNA present is complementary, the duplex-forming oligomers phase-separate into liquid crystal droplets, leaving the unpaired single strands in isotropic solution. In a chemical environment where oligomer ligation is possible, such ordering and condensation would provide an autocatalytic link whereby complementarity promotes the extended polymerization of complementary oligomers.

1 Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309–0390, USA.
2 Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Università di Milano, Milano, Italy.
3 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY 11973, USA.
4 Advanced Photon Source, Argonne National Laboratory, Argonne, IL60439, USA.

* These authors contributed equally to this work.

{dagger} Deceased.

{ddagger} To whom correspondence should be addressed. E-mail: tommaso.bellini{at}unimi.it (T.B.); noel.clark{at}colorado.edu (N.A.C.)

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