Investigating the Interaction Between Folic Acid and Folate Binding Protein at the Single Molecule Level

Abstract

The folic acid-folate receptor recognition interaction has been exploited for targeted drug delivery, yet the detailed mechanism of this binding is unknown. Here, atomic force microscopy was employed to measure the folic acid-folate binding protein interaction. After conjugating a flexible poly(ethylene glycol) linker to folic acid and attaching this to an AFM tip, a controlled mechanical force was applied to disrupt the binding interaction. The amount of force required to cause rupture at various force loading rates were measured. The rupture force dependency on the loading rate characterizes the energy landscape of the single molecule interaction between folic acid and folate binding protein. Control experiments were performed to ascertain the specificity of the FA-FBP single molecule interaction. The use of dynamic force spectroscopy to investigate the details of this binding interaction provides new insight to guide the design of folate receptor-targeting molecules.