AVS 49th International Symposium
    Biomaterials Tuesday Sessions
       Session BI-TuP

Paper BI-TuP13
Transformation of a Single Peptide Molecule Measured with Atomic Force Microscopy

Tuesday, November 5, 2002, 5:30 pm, Room Exhibit Hall B2

Session: Biointerfaces and Surfaces I
Presenter: M. Kageshima, National Institute of Advanced Industrial Science and Technology, Japan
Authors: M. Kageshima, National Institute of Advanced Industrial Science and Technology, Japan
S. Takeda, National Institute of Advanced Industrial Science and Technology, Japan
A. Ptak, Poznan University of Technology
C. Nakamura, National Institute of Advanced Industrial Science and Technology, Japan
S.P. Jarvis, National Institute of Advanced Industrial Science and Technology, Japan
H. Tokumoto, National Institute of Advanced Industrial Science and Technology, Japan
J. Miyake, National Institute of Advanced Industrial Science and Technology, Japan
Correspondent: Click to Email
Transformation of protein molecule is a fundamental process in various function of the molecule. Such a transformation is considered to accompany substantial rearrangement of intramolecular hydrogen bonds. In a peptide molecule in an @alpha@-helix form, breaking of hydrogen bonds takes place as it is unfolded by a tensile force along its helical axis and results in variation in the longitudinal stiffness of the molecule. Therefore, in order to understand the unfolding process in a single-molecule scale, measurement of the variation in stiffness and the energy dissipated during refolding process is indispensable. In the present study this measurement was implemented by AFM with magnetic modulation technique. An end of a single C@sub 3@(AEAAKA)@sub 6@C peptide molecule was picked up with the AFM probe and was stretched. The AFM cantilever was modulated with an AC magnetic force with a frequency of 500 Hz via a magnetic particle on its backside. The amplitude and phase shift in the AC component of the cantilever deflection were measured simultaneously with the DC force. The dissipation during one cycle of oscillation and the variation in the stiffness of the molecule was calculated from the measured amplitude and phase. The contribution by the liquid in the measured dissipation was calculated from the amplitude signal and was subtracted. From the dissipation change during the unfolding process, the dissociation energy per one hydrogen bond was determined. Thus, it is shown that both the conservative and the dissipating processes taking place in a single molecule during its transformation can be measured with this technique.