Imagine being able to rapidly identify tiny biological molecules such as DNA and toxins using a system that can fit on a microchip or in a drop of salt water. It’s closer than you might think, say a team of researchers from the National Institute of Standards and Technology, Brazil’s Universidade Federal de Pernambuco, and Wright State University in Dayton, Ohio.
In a paper appearing next week in the Proceedings of the National Academy of Sciences, the team proves for the first time that a single nanometer-scale pore in a thin membrane—resembling one found in a living cell—can be used to accurately detect and sort different-sized polymer chains (a model for biological molecules) that pass through the channel.
Traditionally, unknown molecules in solution are measured and identified using mass spectrometry, a process that involves ionizing and disintegrating large numbers of the target molecule, then analyzing the masses of the resulting fragments to produce a "molecular fingerprint" for the original sample. The required equipment can cover a good-sized desk. By contrast, the "single-molecule mass spectrometry" system described in the PNAS paper is a non-destructive technique that in principle can measure one molecule at a time in a space small enough to fit on a single microchip-based device the size of a cell phone or PDA.
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