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http://www.technologyreview.com/biotech/19841/ Voltage-sensitive dyes are not new. For decades, neuroscientists have used them to measure voltages across cell membranes in studies of how nerve cells generate and respond to electrical charges. But Kopelman says that it's not possible to control the placement of these dyes in cells. They are hydrophobic and aggregate in cell membranes, so it has not been possible to use them to study the cytosol, the bulk of the interior of the cell. Kopelman also says that these dyes might be reacting with enzymes and other molecules in cells. His encapsulated dyes aren't hydrophobic and can operate anywhere in the cell, not just in membranes. Because it's possible to place his encapsulated dyes in a cell with a greater degree of control, Kopelman likens them to voltmeters. "Nano voltmeters do not perturb [the cellular] environment, and you can control where you put them," he says.
The existence of strong electric fields across cellular membranes is accepted as a basic fact of cell biology. Maintaining gradients of charged molecules and ions allows for many cellular functions, from control over cell volume to the electrical discharges of nerve and muscle cells.
The fact that cells have internal electric fields, however, is surprising. Kopelman presented his results at the annual meeting of the American Society for Cell Biology this month. "There has been no skepticism as to the measurements," says Kopelman. "But we don't have an interpretation."
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