Biocurious is a weblog about biology, quantified.

Molecule of the Month: Designed DNA crystals

by PhilipJ on 6 November 2009

DNA crystal

DNA is a perfect raw material for constructing nanoscale structures. Since base-pairing has been selected by evolution to be highly specific, it is easy to design sequences that will link up with their proper mates. In this way, we can treat small pieces of DNA like Tinkertoys, designing individual components and then allowing them to assemble when we put them together. In addition, the chemistry of DNA synthesis has been completely automated, so custom pieces of DNA can be easily constructed, or even ordered from commercial biotech companies. This puts DNA nanotechnology in the hands of any modest laboratory, and many laboratories have taken advantage of this, creating nanoscale scaffolds, tweezers, polyhedra, computers, and even tiny illustrations composed entirely of DNA.

DNA has the characteristic mix of flexibility and rigidity that is the hallmark of biological molecules. If the sequence of bases is correct, it zips up into a double helix that, at least in short lengths, is a sturdy cylinder. Longer stretches, however, start to show flexibility, and the DNA helix curves and bends. The trick in designing a DNA infrastructure is to develop ways to rigidify the overall structure. In most cases, this has been done by having the DNA strand weave back and forth between many parallel double helices. In this way, the bundle of helices form a structure that is far more rigid than a single helix.

Nadrian Seeman pioneered the use of DNA for building nanoscale structures. After decades of work, the structure shown here, from PDB entry 3gbi, is the first crystal structure of a DNA lattice completely designed from scratch. It is built of small 3D triangular subunits, each composed of three separate types of DNA strands. The base sequences are carefully chosen so that they assemble into this one particular structure, and not any others. At the corners of the 3D triangle, there are sticky ends that link to other triangles, stacking up in a predicable way into a three-dimensional scaffold.

Read the rest from David Goodsell at the RCSB PDB here. We’ve covered some of this kind of work before, too.



  1. Dawn    2705 days ago    #

    That is truly amazing. One thing I cannot understand, is how such intelligent people can believe this all came about from nothing and evolved. All the digital information had to be ‘written’. Please think about it more deeply.
    Fantastic work, I am interested in the VDR.
    take care and God bless ;)


  2. Andre    2704 days ago    #

    Dawn,

    First of all, “evolved” and “came from nothing” are not the same thing. If you’re interested, there are lots of resources online that might make the difference clear. This PBS site on evolution seems a good place to start. Second, for these DNA structures, I agree, they were certainly designed!


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