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Tuesday, April 28, 2015

Mass and shape of single molecules revealed

"A microscopic tool, more than 1000 times thinner than the width of a single human hair, uses vibrations to simultaneously reveal the mass and the shape of a single molecule -- a feat which has not been possible until now." writes Science Daily.

Mathematics Professor John Sader from the University of Melbourne worked with California Institute of Technology experimentalists to invent a new method to weigh and image single molecules.
Photo: Science Daily

The work was led by Professor John Sader at the University of Melbourne's School of Mathematics and Statistics and Professor Michael Roukes of the California Institute of Technology. It features in a paper published in this month's issue of Nature Nanotechnology.

Prof Sader says this technique revolutionises molecule detection for biologists, or indeed anyone who wants to measure extremely small objects.
To discover what a specimen looks like, researchers attach it to a tiny vibrating device, known as a nanoelectromechanical system (NEMS) resonator.

"One standard way to tell the difference between molecules is to weigh them using a technique called mass spectrometry. The problem is that different molecules can have the same weight. Now, we can tell them apart by identifying their shape," Prof Sader said.

"This technology is built on a new mathematical algorithm that we developed, called inertial imaging. It can be used as a diagnostic tool if you're trying to identify, say, a virus or a bacteria particle."
In mass spectrometry, molecules are ionised (or electrically charged) so that an electromagnetic field can interact with them. This interaction is then measured, which gives vital information on the molecule's mass-to-charge ratio.

But this conventional technique has difficulty telling the difference between molecules with similar mass-to-charge ratios, meaning molecule A and molecule B might be very different, but mass-spectrometry can't see this difference.

Additional resources
  1. M. Selim Hanay, Scott I. Kelber, Cathal D. O'Connell, Paul Mulvaney, John E. Sader, Michael L. Roukes. Inertial imaging with nanomechanical systems. Nature Nanotechnology, 2015; 10 (4): 339 DOI: 10.1038/nnano.2015.32
Source: Science Daily