In nanotechnology and molecular biology, researchers are often severely limited by the inability to observe atoms and molecules in three dimensions. Proteins, for instance, fold into complex patterns that are largely invisible to the biologists trying to work out their functions of the biomolecules.
So researchers are working to develop a tool that could provide a 3-D view of the nanoworld. The technology – called magnetic-resonance force microscopy (MRFM) – is a hybrid of magnetic-resonance imaging (MRI) and atomic force microscopy (AFM), which is widely used in nanotech. Physicists at the IBM Almaden Research Center in San Jose, CA, led by Daniel Rugar, recently used MRFM to detect the faint magnetic signal – the “spin” – of a single electron. While that accomplishment is still far from the goal of a 3-D snapshot of an atom or molecule, it is a critical step in proving that MRFM could perform atomic-scale imaging. MRFM works by dangling a tiny magnetic tip from the end of an ultrasensitive cantilever that bends in response to even an exceedingly small force. Under just the right conditions, the magnetic force between the tip and an electron changes the vibrations of the cantilever in a measurable way. Scanning a molecule in a 3-D raster pattern could, in theory, generate an image.
By helping pharmaceutical researchers more directly work out the structures of proteins, MRFM could provide invaluable clues toward the development of safer and more effective drugs. The standard technique for determining the complex three-dimensional structure of proteins involves crystallizing them and then analyzing the diffraction pattern of x-rays that bounce off atoms in the crystal. But not all proteins crystallize, and puzzling out x-ray diffraction patterns is painstaking and tricky.
Researchers at IBM developed the scanning tunneling microscope, which provides images of atoms, and coinvented AFM, which has become a standard tool for atomic-scale manipulation, making possible much of nanotechnology. Whether MRFM will have the same impact is uncertain. But IBM’s experimental result is an encouraging signal for those desperate for a clearer, fuller view of the atomic and molecular world.