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Nanoscale Magnetic Resonance Imaging – The Quest for a Molecular Structure Microscope

Abstract: Can a microscope be built that can directly image the 3D atomic structure of individual biomolecules? Motivated by this question, we are working to dramatically enhance the resolution of magnetic resonance imaging (MRI) using a technique called “magnetic resonance force microscopy” or MRFM. MRFM achieves a 100 million-fold improvement in sensitivity over conventional MRI by replacing the traditional inductive pickup with ultrasensitive detection of magnetic force. Combining this sensitivity improvement with novel methods for spin manipulation, we have successfully detected nanoscale ensembles of nuclear spins, such as 1H, 13C, 19F and 31P. By carefully measuring the magnetic force from the nuclear spins as a function of position, a 3D image of nuclear spin density can be reconstructed. As a first demonstration, we show a 3D reconstruction of the hydrogen in a test sample of tobacco mosaic virus particles. Spatial resolution on the order of 4 nm was obtained. Prospects for pushing the resolution below 1 nm and turning this technique into a useful tool for structural biology will be discussed.
Speaker: Daniel Rugar - IBM Research Division, Almaden Research Center
Speaker Bio: Daniel Rugar is currently Manager of Nanoscale Studies in the IBM Research Division, and a Consulting Professor of Applied Physics at Stanford University. Dr. Rugar has a long history of contributions to the field of scanning microscopy. He began his work in microscopy as a Ph.D. student in Applied Physics at Stanford University, where he developed a gigahertz frequency scanning acoustic microscope operating in superfluid helium with nanometer spatial resolution. He joined IBM in 1984 and made important contributions to the development of atomic force microscopy (AFM) and magnetic force microscopy (MFM), especially for imaging magnetic materials and for applications to data storage. His research group pioneered mechanical detection of ultrasmall forces, achieving the current record of 800 zeptonewtons in a 1 Hertz bandwidth. In 1992, he became inspired by the possibility of combining magnetic resonance imaging (MRI) with ultrasensitive force detection to allow force microscopes to "see" below the surface and take three-dimensional images. He made the first demonstrations of magnetic resonance force microscopy (MRFM) in 1992 and has worked to improve its sensitivity and spatial resolution ever since. After improving the sensitivity by 7 orders of magnitude, this work reached a key milestone in 2004: the manipulation and detection of an individual electron spin. His current work is focused on three-dimensional nanoscale imaging based on MRFM detection of nuclear spins, with a long term goal of developing a microscope that can directly image the 3D atomic structure of molecules. Dr. Rugar has published over 100 scientific papers and holds 19 patents. He was the 1999-2000 Distinguished Lecturer of the IEEE Magnetic Society. He received the 2004 Scientific American 50 award for research leadership in the field of imaging and the 2005 World Technology Award for Materials. He has also received IBM internal awards for contributions to scanning probe microscopy, near field optical data storage and single electron spin detection. He is a fellow of the American Physical Society (APS), the American Association for Advancement of Science (AAAS) and the Institute of Electrical and Electronic Engineers (IEEE).
Poster Link: Poster
Presentation: Presentation on 4/29/2009 (PDF)