AVS 46th International Symposium
    Biomaterial Interfaces Group Wednesday Sessions
       Session BI-WeA

Paper BI-WeA6
Force and Compliance Spectroscopy of Single Peptide Molecule

Wednesday, October 27, 1999, 3:40 pm, Room 613/614

Session: Biology at the Nanoscale
Presenter: H. Tokumoto, JRCAT, Japan
Authors: M.A. Lantz, JRCAT, Japan
S.P. Jarvis, JRCAT, Japan
H. Tokumoto, JRCAT, Japan
T. Martynski, NAIR, Japan
T. Kusumi, NAIR, Japan
C. Nakamura, NAIR, Japan
J. Miyake, NAIR, Japan
Correspondent: Click to Email
An exciting application of AFM to biology is to measure forces required to stretch and unfold individual molecule. This technique looks very promising for studying molecular structure. However, this work has been applied so far to large proteins with complex structures resulting from a variety of bonding mechanisms. This complexity makes the interpretation of the experimental results difficult. Hydrogen bonding plays a major role in the formation of the secondary and tertiary structures of polypeptides from which proteins are composed. Even though, the detailed energy landscapes involved in the formation of these structures are not well understood. Here we demonstrate a new experimental technique for performing single molecule AFM force spectroscopy on significantly smaller molecules than those previously reported. We have used this technique to study the mechanical properties of the synthetic peptide cystein3-lysine30-cystein, which we designed specifically to study hydrogen bonding. Under the experimental conditions used, the peptide adopts the a-helix structure as a result of hydrogen bonding within the molecule. Force-displacement experiments were used to measure the force (approximately 200 pN) required to stretch single peptides from the helical state into a linear chain and the measured force versus peptide elongation was used to calculate the work done in breaking the hydrogen bonds. The average experimental value of the hydrogen bond energy (20.2 kJ/mol) is in good agreement with reported theoretical calculations. In addition, we directly measured the stiffness of the molecule during elongation and found to vary from approximately 0.005 to 0.012 N/m.