Observation of photoactive yellow protein anchored to a modified Au(1 1 1) surface by scanning tunneling microscopy

The adsorption of photoactive yellow protein (PYP) on a Au(1 1 1) surface and its fluorescence activity have been studied by electrochemical scanning tunneling microscopy (EC-STM) and fluorescence photometry. A stable, densely packed protein layer was observed after protein immobilization onto a Au(1 1 1) surface modified with a mixture of 3-mercaptopropanoic acid (3-MPA) and 11-mercaptoundecanoic acid (11-MUA) and subsequent formation of the amide bond with the use of N-hydroxysuccinimide and carbodiimide. Fluorescence photometry data indicate that covalent binding of PYP to the functionalized Au(1 1 1) surface does not interfere with the fluorescence properties of the native protein.