RESEARCH NEWS

DECEMBER 2011 | VOLUME 14 | NUMBER 12574

Materials scientists would like to exploit the

exponentially self-replicating information storage

system that is DNA to build their own designer nano

structures with specific functions and properties. The

first tentative steps towards such a system have now

been taken by researchers in the US [N.C. Seeman

et al., Nature (2011) doi:10.1038/nature10500].

DNA is well known for its self-organizing and self-

assembly properties.

Recently, however, researchers have demonstrated

how it can also organize other molecules as well

as metallic particles, forming quite sophisticated

structures. Nadrian Seeman, Paul Chaikin, and

colleagues at New York University have now

constructed tile motifs from strands of synthetic

DNA that recognize and bind complementary

tiles in a pre-programmed manner to make more

complex structures. The process generates seven-tile

seed sequences that then go on to produce a new

generation of complementary seven-tile daughter

sequences and then a generation of granddaughter

tiles that are identical to the initial seeds. The whole

process works without the need for the normal cellular

components and enzymes of DNA organization,

although it requires several chemical and thermal

steps.

Natural DNA uses a four-letter alphabet of adenine

(A), thymine (T), guanine (G), and cytosine (C). A is the

complement of T; G of C. The NYU team developed

an artificial tile or motif, called BTX (bent triple helix

molecules containing three DNA double helices), with

each BTX molecule composed of 10 DNA strands

including four single-stranded “sticky ends” that are

used to recognize across generations. Unlike DNA, the

code from these four sticky ends is not limited to the

four base letters. The complementarity of the units

means that in principle there could be quadrillions

of different letters and tiles that pair up to form a

six-helix construct as a building block for complex

structures and patterns.

Indeed, the researchers hint that their work offers the

possibility of making self-replicating materials with any

of a wide range of patterns for a variety of functions

from this almost limitless alphabet of artificial DNA

units. The self-replication in the system, which carries

complex information from one molecular generation

to the next makes this study an important step

towards designer materials.

“This is the first step in the process of creating artificial

self-replicating materials of an arbitrary composition,”

explains team member Paul Chaikin. “The next

challenge is to create a process in which self-replication

occurs not only for a few generations, but long enough

to show exponential growth.” The next step will be to

develop the technology so that it can be carried out

in a single-pot process that does not require multiple

chemical and thermal processing cycles.

David Bradley

Designer nano structuresNANOTECHNOLOGY

DNA tile sequences and structures. Reprinted by permission from Macmillan Publishers Ltd: Nature, 478, 225, © 2011.

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Biosensors 2012ANNOUNCEMENTS

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