A Close Look at Proteins: Submolecular Resolution of Two- and Three-Dimensionally Folded Cytochrome c at Surfaces

Abstract

Imaging of individual protein molecules at the single amino acid level has so far not been possible due to the incompatibility of proteins with the vacuum environment necessary for high-resolution scanning probe microscopy. Here we demonstrate electrospray ion beam deposition of selectively folded and unfolded cytochrome c protein ions on atomically defined solid surfaces in ultrahigh vacuum (10(-10) mbar) and achieve unprecedented resolution with scanning tunneling microscopy. On the surface folded proteins are found to retain their three-dimensional structure. Unfolded proteins are observed as extended polymer strands displaying submolecular features with resolution at the amino acid level. On weakly interacting surfaces, unfolded proteins refold into flat, irregular patches composed of individual molecules. This suggests the possibility of two-dimensionally confined folding of peptides of an appropriate sequence into regular two-dimensional structures as a new approach toward functional molecular surface coatings.

Single-Molecule Imaging of Gold-Binding Peptide Adsorbed on Au(111)

“…The spatial resolution of Fig. 4b is comparable to that of the recently reported STM image of cytochrome c. 39 The cytochrome c was carefully adsorbed on metal surfaces by electrospray ion beam deposition, and STM imaging was conducted in an ultrahigh vacuum condition. In the present study, the sample peptide was adsorbed simply by spin-coating and observed in an ambient condition; nevertheless, the similar resolution was achieved for 1GBP.…”

Facet-Specific Adsorption of Tripeptides at Aqueous Au Interfaces: Open Questions in Reconciling Experiment and Simulation

“…18,19 However, AFM is unable to resolve the structure of the peptide chains at the desired level of detail. Moreover, it is likely that the drying process will affect the structure of the peptide assemblies.…”

Synthesis of One‐Dimensional Schiff Base Polymers that Contain an Oligothiophene Building Block on the Graphite Surface

“…[38] In these studies, rigid component molecules were usually employed to build polymers of different dimensions, whereas increasing attention has been given to the adsorption and on-surface synthesis of much larger and more flexible species. [39][40][41][42] The Schiff base reaction has been widely applied in dynamic covalent chemistry, [43,44] and it has also been investigated both under UHV and ambient conditions by means of scanning tunneling microscopy (STM). [23][24][25][32][33][34][35] The reactions, particularly those that result in small-molecule imine compounds, can proceed under room temperature, [32,43] whereas for the preparation of high-quality surface 2D polymers, mild heating is normally necessary.…”