AVS 49th International Symposium
    Molecular and Bio-Magnetism Tuesday Sessions
       Session MB+BI+OF-TuA

Invited Paper MB+BI+OF-TuA5
Measuring and Manipulating Single Molecules Inside Living Cells

Tuesday, November 5, 2002, 3:20 pm, Room C-205

Session: Molecular and Bio-Magnetism
Presenter: J.S. Kanger, University of Twente, The Netherlands
Authors: J.S. Kanger, University of Twente, The Netherlands
A.H.B. de Vries, University of Twente, The Netherlands
J. Greve, University of Twente, The Netherlands
B. Krenn, University of Amsterdam, The Netherlands
R. van Driel, University of Amsterdam, The Netherlands
Correspondent: Click to Email
For manipulating single molecules, techniques like AFM or optical tweezers are typically used. However, the actual actuators of these systems are relatively large, and therefore we are not able to manipulate single molecules that are situated deep inside the cell (for example inside the nucleus), without causing massive damage to the cell itself. We describe a conceptual simple arrangement for manipulating ultra small magnetic beads inside living cells using magnetic forces. By using magnetic forces to manipulate the bead, and a low yield HeNe laser to measure its position, we are able to generate a relatively high force, without damaging the cell. The setup is designed to measure the movement of a bead with nanometer precision, and apply picoNewton forces on it. Experimental results combined with model calculations show that a force of 15 pN is feasible for a ferrite bead of 50 nm diameter. If a bead is attached to a functioning protein the movement of this protein in the cell can be monitored and manipulated. We plan to apply this technique to the study of chromatin structure function relations inside the living cell. The magnetic force on a bead is proportional to the magnetization of the bead, and the gradient of the magnetic field. To produce a magnetic field that gives a gradient that is controllable both in direction and strength we constructed a four pole configuration. The tips of these poles (5 µm width and height) are placed 20 µm from each other, which leaves enough space to place a cell, with a magnetic bead in the nucleus, between the poles. The magnetic field is guided from external coils to the poletip that becomes magnetically saturated (1.8 Tesla). The pole tips are produced in the cleanroom facilities of our university. Bead position detection is done by back focal plane interferomtery. A low-yield HeNe laser will is focused on the bead. The combination of the laserbeam and, and the forward scattered light gives a interference pattern on a quadrant detector, which is depended on the position of the bead in the focus.