FOR RELEASE: Tuesday, March 17, 1998, 2:30 PM

Feeling Biomolecules with the Atomic Force Microscope

Helen G. Hansma (hhansma@physics.ucsb.edu)
Department of Physics
University of California
Santa Barbara, CA

Lay Language Description of Paper K5.01
Presented Tuesday, March 19
1998 APS March Meeting, Los Angeles

The atomic force microscope (AFM) feels the surfaces of molecules, much as a record stylus feels the surface of a phonograph record . Most molecules are buried within cells, where the AFM cannot feel them without disrupting the cell. There is an important group of molecules outside of the cells, however, which is called the extracellular matrix (ECM) or 'Basement Membrane.' These molecules were long ignored, much as the packing materials in a box are ignored and discarded when one removes the objects packed in the box . It is turning out that the ECM molecules are vitally important to cells. ECM molecules bind to receptor molecules on the surface of the cell and send signals that regulate which genes are active in the cell. One of the major ECM molecules is Laminin, a large cross-shaped protein. The AFM can feel laminin molecules on a surface and map the positions of the laminin arms and their lumps, as shown below . These laminin molecules are on a flat mica surface in air. Collagen IV is also part of the ECM; the AFM can probe the interactions of laminin and collagen.

In addition to feeling molecules in air, the AFM can feel molecules in aqueous solution, even when they are moving on a surface, if the movement is not too rapid. The laminin molecule shown below stayed attached to the mica surface, but its arms moved. These arm movements may be important in regulating how laminin interacts with cells and other ECM molecules.

The website below has more information about how the AFM works and about feeling biomolecules with the AFM, especially DNA.

http://www.physics.ucsb.edu/~hhansma/