Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Differentiating Left- and Right-Handed Carbon Nanotubes by DNA



Ming Zheng, Geyou Ao, Jason K. Streit, Jeffrey A. Fagan


The emergence of macromolecules of defined structures is a crucial step in the evolution of life. The mechanism by which these structures are selected from astronomical numbers of biopolymer sequences has long been a topic of controversy1,2. Experimenting structure selection from man-made macromolecular libraries may shed light to the mechanism of natural selection, and may also lead to the discovery of novel materials for technological applications. DNA-wrapped single-wall carbon nanotubes3-5 form a man-made library of enormous size due to the combinatorial diversity of nanotube structure and DNA sequence. Here, we report the use of polymer aqueous two-phase systems to select special DNA-wrapped carbon nanotubes, each of which has an ordered DNA structure bound to a nanotube of defined handedness, resembling a well-folded biomacromolecule with innate stereo-selectivity. By screening over 300 DNA sequences, we are able to achieve unprecedented nanotube enantiomer selection across the entire chiral angle range. The screening has also identified a rare DNA sequence that adopts two distinct folds on a pair of nanotube enantiomers, respectively, rendering them large differences in fluorescence intensity and chemical reactivity. This finding establishes a first example of functionally distinguishable right- and left-handed nanotubes. Mechanistic analysis, aided by structure-specific nanotube optical transitions6, suggests that sensitive dependence of hydration energy on structure variation makes conformational entropy minimization an implicit criterion in the aqueous two-phase selection, resulting in exquisite selectivity towards ordered structures. Our study introduces a new method to select well-folded bio- and bio/nano-molecules, and suggests a hydration energy driven mechanism that could be operative in the natural selection of biomacromolecules.
Journal of the American Chemical Society


carbon nanotubes, DNA, selection, aqueous two-phase


Zheng, M. , Ao, G. , Streit, J. and Fagan, J. (2016), Differentiating Left- and Right-Handed Carbon Nanotubes by DNA, Journal of the American Chemical Society (Accessed December 3, 2023)
Created December 28, 2016, Updated March 17, 2017