Single molecule force spectroscopy: a new tool for bioinorganic chemistry

Metalloproteins are essential in biology. The incorporation of metal ion into metalloproteins significantly expands protein functionality and enhances protein stability. Over the last few years, atomic force microscopy-based single molecule force spectroscopy (SMFS) has evolved into a unique tool allowing for probing metalloproteins and metal-ligand bonds one molecule/bond at a time. Mechanical strength of a wide variety of metal-ligand bonds has been measured in metal-ligand complexes as well as in metalloproteins, providing detailed information of their underlying free energy profiles and the influence of the protein environment on the bond strength. SMFS experiments have directly demonstrated the effect of the metal binding on the mechanical stability of proteins. Moreover, SMFS has enabled the direct observation of the unfolding and folding of metalloproteins, revealing detailed mechanistic insight into the unfolding pathways modulated by the metal center.