Designer DNA snaps into holey crystals

While attempting to cocrystallize DNA and protein molecules, Paul J. Paukstelis, a crystallographer with the Institute of Cellular & Molecular Biology at the University of Texas, Austin, was disappointed: Only the DNA crystallized. Then Paukstelis wondered if he could design DNA oligomers that would assemble into crystals with a regular network of pores that could host hard-to-crystallize proteins and other molecules with a regularity amenable to crystallographic analyses. By designing oligomers that exhibit both classic binding between C−G and T−A nucleotides and nonclassical pairings such as A−A and G−G, he has taken "a first step," he reports. When he expands these "assembly strands" with spacer strands, the expanded oligonucleotides self-assemble into sugar-grain-size crystals with long-range, 9-nm pores along one of the crystal's directions. Paukstelis reports that proteins below a threshold size infiltrate these pores but larger molecules do not, a trait important for the applications he has in mind (J. Am. Chem. Soc., published online May 9, dx.doi.org/10.1021/ja061332r).