The synthesis of ultra-small gold nanoclusters (Au NCs) with sizes down to 2 nm has received increasing interest due to their unique optical and electronic properties. Like many peptide-coated gold nanospheres synthesized before, modified gold nanoclusters with peptide conjugation are potentially significant in biomedical and catalytic fields. Here, we explore whether such small-sized gold nanoclusters can be conjugated with peptides also and characterize them using atomic force microscopy. Using a long and flexible elastin-like polypeptide (ELP)20 as the conjugated peptide, (ELP)20-Au NCs was successfully synthesized via a one-pot synthesis method. The unique optical and electronic properties of gold nanoclusters are still preserved, while a much larger size was obtained as expected due to the peptide conjugation. In addition, a short and rigid peptide (EAAAK)3 was conjugated to the gold nanoclusters. Their Yong’s modulus was characterized using atomic force microscopy (AFM). Moreover, the coated peptide on the nanoclusters was pulled using AFM-based single molecule-force spectroscopy (SMFS), showing expected properties as one of the first force spectroscopy experiments on peptide-coated nanoclusters. Our results pave the way for further modification of nanoclusters based on the conjugated peptides and show a new method to characterize these materials using AFM-SMFS.

Lead is a toxic metal harmful to human beings because of its long history and wide use in human society. The interaction of lead with proteins is one of the most common ways it exerts toxicity. Due to its thiophilic property, lead targets thiol-rich proteins with high affinity and forms stable Pb−S bonds, which may replace the originally bound metal ion and incapacitate the protein/enzyme. Thus, the knowledge of the Pb−S bonds in proteins is important. To study Pb−S bonds, we chose a de novo designed protein α 3 DIV, able to bind Pb(II) via its three cysteines, as the model protein.Using atomic force microscopy-based single-molecule force spectroscopy (AFM-SMFS), we proved the formation of a triangular pyramidal PbS 3 site in α 3 DIV by detecting specific Pb−S bond rupture signals, including the previously undetected Pb− S(Cys67) bond. Moreover, the pH-dependent weakening of Pb−S bond strength was revealed and quantified, leading to the dissociation of the PbS 3 site at pH 4.5.