Dynamic single molecule force spectroscopy

Individual Supramolecular Host-Guest Interactions Probed by Dynamic Single Molecule Force Spectroscopy... 

In conclusion, the complexation behavior of ferrocene moieties in highly ordered SAMs of P-CD on Au(l 11) was investigated by dynamic single molecule force spectroscopy. Multiple pull-off events were observed for the interaction between ferrocene (immobilized in a mixed hydroxyl-ferrocene SAM on an AFM tip) and p-CD SAM on Au(l 11) in water. Addition of a guest (1,8-ANS) causes reversible blocking of the cavities. The adhesion between P-cyclodextrin and ferrocene moieties was found to be a multiple of 56 10 pN. The observed "quantum" of adhesion force can be identified as the value for a single rupture force of the ferrocene - p-CD complex. This force was found to be independent of the (un-)loading rate between 2.00 x 10 and 2.34 x 10 pN/s. 

In AFM single molecule dynamic force spectroscopy (AFM-FS), binding forces between two molecules of interest are measured by functionally immobilizing them on two different surfaces (i.e. the tip of an AFM and an appropriate counter surface) that are brought in mechanical contact under physiological conditions (see Figure 2). 

The ramifications of nanotechnology in the food arena have yet to be fully realized. This requires further research into biopolymer assembly behavior and applications of nanomaterials in the food industry. Researchers should keep abreast of the development of research tools and what is being done to push resolution limits for techniques such as atomic force spectroscopy or the synchrotron coupled to various spectroscopic techniques and higher resolution microscopy. New techniques should be exploited and the knowledge gained used to understand the dynamics and interactions of food materials at the single-molecule level and to describe assembly behavior in quantitative thermodynamic terms. There are questions about the interactions of nanoparticles with the food matrix and within the human body. These questions need to be addressed by future research (Simon and Joner, 2008 Sletmoen et ah, 2008). 

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