Single-walled carbon nanotubes (SWNTs) show great promise as components of nanoscale electronic devices, but most commercial applications have been stymied by the difficulty in isolating nanotubes of identical chirality from a synthetic mixture.
Now, Xiaomin Tu and Ming Zheng of DuPont Central Research & Development, together with Suresh Manohar and Anand Jagota of Lehigh University, have shown that the unique molecular properties of DNA can be exploited to sort SWNTs (Nature 2009, 460, 250).
[A DNA sequence consisting of ATTT repeats forms a barrel-shaped structure around a single type of chiral carbon nanotube.]
Single walled nanotubes synthesis produces a mixture of nanotubes with nonuniform diameters and chiralities and, therefore, heterogeneous physicochemical properties. Having previously shown that a particular DNA sequence could form an ordered structure on SWNTs, Zheng and colleagues reasoned that they might be able to find a DNA sequence to purify each type of SWNT in a synthetic mixture. The problem was identifying the correct DNA molecules among an unfeasibly large number (1018) of possible 30-nucleotide sequences.
To reduce the DNA library to a more manageable size of 350 oligonucleotides, the researchers devised a sequence-pattern-expansion scheme that considered all possible DNA sequences composed of mono-, di-, tri-, and tetranucleotide repeats. They added each DNA oligonucleotide to a random mixture of SWNTs. Then, they used ion-exchange chromatography to separate the 350 solutions into fractions, which they analyzed spectroscopically for the presence of specific DNA-SWNT hybrids.
[Source: ACS]
Now, Xiaomin Tu and Ming Zheng of DuPont Central Research & Development, together with Suresh Manohar and Anand Jagota of Lehigh University, have shown that the unique molecular properties of DNA can be exploited to sort SWNTs (Nature 2009, 460, 250).
[A DNA sequence consisting of ATTT repeats forms a barrel-shaped structure around a single type of chiral carbon nanotube.]
Single walled nanotubes synthesis produces a mixture of nanotubes with nonuniform diameters and chiralities and, therefore, heterogeneous physicochemical properties. Having previously shown that a particular DNA sequence could form an ordered structure on SWNTs, Zheng and colleagues reasoned that they might be able to find a DNA sequence to purify each type of SWNT in a synthetic mixture. The problem was identifying the correct DNA molecules among an unfeasibly large number (1018) of possible 30-nucleotide sequences.
To reduce the DNA library to a more manageable size of 350 oligonucleotides, the researchers devised a sequence-pattern-expansion scheme that considered all possible DNA sequences composed of mono-, di-, tri-, and tetranucleotide repeats. They added each DNA oligonucleotide to a random mixture of SWNTs. Then, they used ion-exchange chromatography to separate the 350 solutions into fractions, which they analyzed spectroscopically for the presence of specific DNA-SWNT hybrids.
[Source: ACS]
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