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Microscopic scaffolding to house the tiny components of nanotech devices

could be built from RNA

Published: Thursday, 12-Aug-2004 News-Medical.Net

Microscopic scaffolding to house the tiny components of nanotech devices

could be built from RNA, the same substance that shuttles messages

around a cell's nucleus, reports a Purdue University research group.

By encouraging ribonucleic acid (RNA) molecules to self-assemble into

3-D shapes resembling spirals, triangles, rods and hairpins, the group

has found what could be a method of constructing lattices on which to

build complex microscopic machines. From such RNA blocks, the group has

already constructed arrays that are several micrometers in diameter –

still microscopically small, but exciting because manipulating

controllable structures of this size from nanoparticles is one of

nanotechnology's main goals.

" Our work shows that we can control the construction of

three-dimensional arrays made from RNA blocks of different shapes and

sizes, " said Peixuan Guo, who is a professor of molecular virology in

Purdue's School of Veterinary Medicine. " With further research, RNA

could form the superstructures for tomorrow's nanomachines. "

The paper, which Guo co-authored with Dan Shu, Wulf-Dieter Moll,

Zhaoxiang Deng and Chengde Mao, all of Purdue, appears in the August

issue of the journal Nano Letters.

Nanotechnologists, like those in Guo's group, hope to build microscopic

devices with sizes that are best measured in nanometers – or billionths

of a meter. Because nature routinely creates nano-sized structures for

living things, many researchers are turning to biology for their

inspiration and construction tools.

" Biology builds beautiful nanoscale structures, and we'd like to borrow

some of them for nanotechnology, " Guo said. " The trouble is, when we're

working with such tiny blocks, we are short of tiny steam shovels to

push them around. So we need to design and construct materials that can

assemble themselves. "

Organisms are built in large part of three main types of building

blocks: proteins, DNA and RNA. Of the three, perhaps least investigated

and understood is RNA, a molecular cousin to the DNA that stores genetic

blueprints within our cells' nuclei. RNA typically receives less

attention than other substances from many nanotechnologists, but Guo

said the molecule has distinct advantages.

" RNA combines the advantages of both DNA and proteins and puts them at

the nanotechnologist's disposal, " Guo said. " It forms versatile

structures that are also easy to produce, manipulate and engineer. "

Since his discovery of a novel RNA that plays a vital role in a

microscopic " motor " used by the bacterial virus phi29 (see related

story), Guo has continued to study the structure of this RNA molecule

for years. It formed the " pistons " of a tiny motor his lab created

several years ago, and members of the team collaborated previously to

build dimers and trimers – molecules formed from two and three RNA

strands, respectively. Guo said the methods the team used in the past

made their recent, more comprehensive construction work possible.

" By designing sets of matching RNA molecules, we can program RNA

building blocks to bind to each other in precisely defined ways, " he

said. " We can get them to form the nano-shapes we want. "

From the small shapes that RNA can form – hoops, triangles and so forth

– larger, more elaborate structures can in turn be constructed, such as

rods gathered into spindly, many-pronged bundles. These structures could

theoretically form the scaffolding on which other components, such as

nano-sized transistors, wires or sensors, could be mounted.

" Because these RNA structures can be engineered to put themselves

together, they could be useful to industrial and medical specialists,

who will appreciate their ease of engineering and handling, " said Dieter

Moll, a postdoctoral researcher in Guo's lab. " Self-assembly means

cost-effective. "

Moll, while bullish on RNA's prospects, cautioned that there was more

work to be done before nanoscale models could be built at will.

" One of our main concerns right now is that, over time, RNA tends to

degrade biologically, " he said. " We are already working on ways to make

it more resistant to degradation so that it can form long-lasting

structures. "

Guo said that though applications might be many years away, it would be

most productive to take the long-term approach.

" We have not built actual scaffolds yet, just 3-D arrays, " he said. " But

we have built them from engineered biological molecules, and that could

help us bridge the gap between the living and the nonliving world. If

nanotech devices can eventually be built from both organic and inorganic

materials, it would ease their use in both medical and industrial

settings, which could multiply their usefulness considerably. "

http://www.purdue.edu/