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Posted: Oct 06, 2011
Nanopores on a chip
(Nanowerk News) Biological nanopores are proteins of only a few nanometers in diameter that form tiny water-filled canals. They have proven to be promising tools in the field of nanobiotechnology. In a joint project at the University of Freiburg, a research group led by Prof. Dr. Jan C. Behrends, Institute of Physiology, and scientists working under Prof. Dr. Jürgen Rühe, Department of Microsystems Technology (IMTEK), have succeeded in arranging nanopores on a tiny microchip and using it to determine the mass of chain-like molecules, so-called polymers, with a high degree of precision.
In these experiments, the nanopores assume the role of the actual sensor. The first author of the study, now published in the renowned journal ACS Nano of the American Chemical Society ("Nanopore-Based Single-Molecule Mass Spectrometry on a Lipid Membrane Microarray"), Dr. Gerhard Baaken, hopes that the new development will be instrumental in exploiting the great potential of nanopore analysis for chemistry and the life sciences.
In their natural environment, nanopores often have the function of transporting larger molecules. For instance, they convey proteins through membranes. Bacteria also use nanopores to destroy the cells of infected organisms. This is also true of alpha-hemolysin, a protein produced by staphylococci to destroy red blood cells. This protein has also recently found applications in analytical tasks in chemistry and biology. If a large-sized molecule gets into the pore, it becomes partially blocked for fractions of a second.
By measuring the electrical conductivity of the hemolysin pore, scientists can detect the presence of a single molecule—in a fashion similar to the function of a light barrier. By the same principle it is also possible to make a very precise measurement of the size of the molecule. Scientists are very optimistic about the potential applications—not only for the analysis of synthetic polymer mixtures, but also for the analysis of genetic material and even as a quick and inexpensive way to sequence DNA.
The Freiburg research team has now succeeded in conducting such measurements on a specially developed biohybrid microsensor made of biological and micro-technical parts. It contains 16 miniaturized artificial cell membranes on only one square millimeter. The individual membranes are spread over minuscule pits, each with a diameter of approximately two-hundredths of a millimeter. That is the equivalent of around one-third of the thickness of a human hair. In their publication, the authors demonstrate that they can use the chip to obtain the distributions of polymer sizes that are accurate to a single chain element. Currently, results of such precision require expensive equipment filling entire rooms. The project is a good example of successful collaboration among strongly diverging disciplines.