The first self-assembled nanostructures composed entirely of glycerol nucleic acid (GNA, —a synthetic analog of DNA)have been made by Biodesign Institute scientist John Chaput and his research team.
The only chemical difference between DNA and a synthetic cousin, GNA, is in the sugar molecule. GNA uses a three-carbon sugar called glycerol rather than the five-carbon deoxyribose used in DNA. The sugar provides the chemical backbone for nucleic acid polymers, anchoring a phosphate molecule and nitrogenous base (B). Credit: Biodesign Institute at Arizona State University
The five carbon sugar commonly found in DNA, called deoxyribose, is substituted by glycerol, which contains just three carbon atoms.
The first self-assembled DNA nanostructure was made by Ned Seeman’s lab at Columbia University in 1998, the very same laboratory where ASU professor Hao Yan received his Ph.D. Chaput’s team, which includes graduate students Richard Zhang and Elizabeth McCullum were not only able to duplicate these structures, but, unique to GNA, found they could make mirror image nanostructures.
“Making GNA is not tricky, it’s just three steps, and with three carbon atoms, only one stereo center,” said Chaput. “It allows us to make these right and left-handed biomolecules. People have actually made left-handed DNA, but it is a synthetic nightmare. To use it for DNA nanotechnology could never work. It’s too high of a cost to make, so one could never get enough material.”
The ability to make mirror image structures opens up new possibilities for making nanostructures. The research team also found a number of physical and chemical properties that were unique to GNA, including having a higher tolerance to heat than DNA nanostructures. Now, with a new material in hand, which Chaput dubs ‘unnatural nucleic acid nanostructures,’ the group hopes to explore the limits on the topology and types of structure they can make.
“We think we can take this as a basic building block and begin to build more elaborate structures in 2-D and see them in atomic force microscopy images,” said Chaput. “I think it will be interesting to see where it will all go. Researchers come up with all of these clever designs now.”