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Title: Single ricin detection by AFM chemomechanical mapping

item CHEN, GUOJUN - University Of Georgia
item ZHOU, JIANFENG - University Of Georgia
item XU, BINGQIAN - University Of Georgia
item Park, Bosoon

Submitted to: Chemical Physics Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/12/2009
Publication Date: 7/27/2009
Citation: Chen, G., Zhou, J., Xu, B., Park, B. 2009. Single ricin detection by AFM chemomechanical mapping. Applied Physics Letter 95: doi:10.1063/1.3190197.

Interpretive Summary: Nanotechnology has the potential to revolutionize agricultural and food system. With the development in nanotechnology, nanobiosensors for detecting food toxin are important in food safety and biosecurity. Ricin is a protein toxin that can be extracted from the castor bean. Intoxication of very small quantities, less than half a grain of sand, can cause allergic reactions or be fatal. Consequently, any detection systems need to have high sensitivity, specificity and speed. In this paper, a new detection method for ricin at the nano and sub-nano scale using AFM-based single molecule interaction recognition is presented. The methodologies and protocols used have the potential for the rapid detection of other biological agents and toxins with high sensitivity and specificity.

Technical Abstract: This research reports a method of detecting ricin molecules immobilized on chemically modified gold (Au;111) surface by chemomechanically mapping the molecular interactions with a chemically modified Atomic Force Microscope (AFM) tip. AFM images resolved the different fold-up conformations of single ricin molecule as well as their intra-molecule structure of A- and B- chains. AFM force spectroscopy study of the interaction indicates that the unbinding force has a linear relation with the logarithmic force loading rate, which agrees well with calculations using one-barrier bond dissociation model. Further, the activation energy was obtained by combining Bell model and Jarzynski's equality.