Single Molecule Recognition between Cytochrome C 551 and

ABSTRACT Recent developments in single molecule force spectroscopy have allowed investigating the interaction between two redox partners, Azurin andCytochromeC551. Azurin has been directly chemisorbed on a gold electrodewhereas cytochrome c has been linked to the atomic force microscopy tip by means of a heterobifunctional flexible cross-linker. When recording force-distance cycles,molecular recognition events could be observed, displaying unbinding forces of;95 pN for an applied loading rate of 10 nN/s. The specificity of molecular recognition was confirmed by the significant decrease of unbinding probability observed in control block experiments performed adding free azurin solution in the fluid cell. In addition, the complex dissociation kinetics has been here investigated bymonitoring the unbinding forces as a function of the loading rate: the thermal off-ratewas estimated to be;14 s1,much higher than values commonly estimated for complexesmore stable than electron transfer complexes. Results here discussed represent the first studies on molecular recognition between two redox partners by atomic force microscopy