Single Polymer Chains as Specific Transducers of Molecular Recognition in Scanning Probe Microscopy

摘要

A new approach for the specific detection and mapping of single molecule recognition is presented,based on the nonlinear elastic behavior of a single polymer chain.The process of molecular recognition between a ligand and a receptor is inherently accompanied by a decrease in the translational and rotational degrees of freedom of the two molecules.We show that a polymeric tether linked to the ligand can effectively transduce the configurational constraint imposed by molecular recognition into a measurable force,which is dominated by the entropic elasticity of the polymer.This force is specifically characterized by a strong nonlinearity when the extension of the polymer approaches its contour length.Thus,a polymer chain tethering the ligand to an oscillating cantilevered tip gives rise to a highly anharmonic motion upon ligand-receptor binding.Higher-harmonics atomic force microscopy allows us to detect this phenomenon in real time as a specific signature for the probing and mapping of single-molecule recognition.