Watching molecules grow into microtubes

February 22, 2013

Sometimes the best discoveries come by accident. A team of researchers at Washington University in St. Louis, headed by Srikanth Singamaneni, PhD, assistant professor of mechanical engineering & materials science, unexpectedly found the mechanism by which tiny single molecules spontaneously grow into centimeter-long microtubes by leaving a dish for a different experiment in the refrigerator.

Once Singamaneni and his research team, including Abdennour Abbas, PhD, a former postdoctoral researcher at Washington University, Andrew Brimer, a senior undergraduate majoring in , and Limei Tian, a fourth-year graduate student, saw that these molecules had become microtubes, they set out to find out how.

To do so, they spent about six months investigating the process at various length scales (nano to micro) using various microscopy and spectroscopy techniques.

The results were published in the journal Small.

This video is not supported by your browser at this time.

"What we showed was that we can actually watch the self-assembly of across multiple length scales, and for the first time, stitched these length scales to show the complete picture," Singamaneni says. "This hierarchical self-organization of molecular building blocks is unprecedented since it is initiated from a single molecular crystal and is driven by vesiclular dynamics in water."

Self-assembly, a process in which a disordered collection of components arrange themselves into an ordered structure, is of growing interest as a new paradigm in creating micro- and nanoscale structures and functional systems and subsystems. This novel approach of making nano- and microstructures and devices is expected to have numerous applications in electronics, optics and biomedical applications.

The team used small molecules p-aminothiophenol (p-ATP) or p-aminophenyl disulfide added to water with a small amount of ethanol. The molecules first assembled into nanovesicles then into microvesicles and eventually into centimeter-long microtubules. The vesicles stick onto the surface of the tube, walk along the surface and attach themselves, causing the tube to grow longer and wider. The entire process takes mere seconds, with the growth rate of 20 microns per second.

"While it was exciting to watch the self-assembly of these molecules, we are even more excited about the implications of the self-assembly of such small molecules," Singamaneni says. "This mechanism can be used to load the vesicles with the desired macromolecules, such as proteins, antibodies or antibiotics, for example, and build microtubes with a biological function."

Singamaneni says his research team collaborated with researchers in Singapore who are experts in molecular crystals, as well as with colleagues in the Department of Chemistry.

"We hope that once we can co-assemble some functional nanostructures along with these small molecules, then these molecular assemblies can have applications in biological sensors and chemical sensors," Singamaneni says.

Explore further: World first as scientists grow microtubes from crystals (Video)

More information: Abbas A, Brimer A, Tian L, d'Avignon D, Hameed A, Vittal J, Singamaneni S. "Vesicle-Mediated Growth of Tubular Branches and Centimeter-Long Microtubes from a Single Molecule." Small. Early online publication Dec. 16, 2012.

Related Stories

Liverpool scientists construct molecular 'knots'

July 20, 2010

Scientists at the University of Liverpool have constructed molecular 'knots' with dimensions of around two nanometers -- around 30,000 times smaller than the diameter of a human hair.

Recommended for you

Physicists develop new technique to fathom 'smart' materials

November 26, 2015

Physicists from the FOM Foundation and Leiden University have found a way to better understand the properties of manmade 'smart' materials. Their method reveals how stacked layers in such a material work together to bring ...

Mathematicians identify limits to heat flow at the nanoscale

November 24, 2015

How much heat can two bodies exchange without touching? For over a century, scientists have been able to answer this question for virtually any pair of objects in the macroscopic world, from the rate at which a campfire can ...

New sensor sends electronic signal when estrogen is detected

November 24, 2015

Estrogen is a tiny molecule, but it can have big effects on humans and other animals. Estrogen is one of the main hormones that regulates the female reproductive system - it can be monitored to track human fertility and is ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.