Development of a High-Speed Atomic Force Microscope Combined with a High-resolution Optical Microscope for Biological Studies
Dr. Byung Kim
In the life sciences, it has long been a dream to view the nanometer-scale dynamic behavior of individual biomolecules, such as proteins in solution. Biomolecules perform very specific and sophisticated physiological functions. For example, motor proteins such as myosin, kinesin, and dynein produce force to pull cytoskeletal fibers, or to move along these fibers. These physiological actions are determined by a very specific three-dimensional structure of biomolecules in action. Knowledge of the biomolecular fine structure with atomic resolution is essential for understanding the physiological function, and can be studied with X-ray crystallography and electron microscopy (EM). However, EM and x-ray crystallography have a limited ability to reveal physiological function because they do not directly allow for the study of living species. For EM, there is no information on the time axis, because the image is static. X-ray studies do not reveal the structure of biomolecules in a physiological environment. The biomolecular structural dynamics of biomolecules, non-fixated, are the most difficult to study because the time scale of their action may range from a nanosecond to a second. High speed atomic-force microscopy (HSAFM) has made it possible to view living biomolecules with atomic resolution in a physiological environment at the biomolecular time scale. However, the HSAFM is currently limited to surface topographic features on the membrane surface of a cell without visualizing processes inside the cell. As an approach to address this issue, we have designed and developed a HS AFM capable of acquiring AFM and optical images simultaneously, thus providing comprehensive understanding of biomolecular processes in a cell. The HSAFM is also capable of imaging small molecules as well as bigger cellular structures, extending the application range from cellular systems to biomolecules. The current data acquisition speed of AFM a speed of 5.6 seconds/frame is enough to capture biomolecules in motion and optical resolution of 446 nm is enough to track the transportation processes across the membrane. In conjunction with high resolution optical microscopy, the HS AFM will contribute to the study of biomolecular dynamics with nanometer resolution on the delicate cellular surfaces.