We develop a new technique called photo-induced force microscopy (PiFM), which allows us to image the chemical makeup of samples with extremely high spatial resolution. We spent some time to image isolated protein particles and obtained results that may be consistent with the design of the protein cage.
A Single Self-assembled Icosahedral Protein Cage Imaged via PiFM
This novel nanoscale icosahedral protein cage (theoretical edge length of 7 nm and ~14 nm volume diagonal) is designed to self-assemble using simple protein building blocks. A single protein cage is imaged via PiFM. While AFM topography image shows a nominally spherical shape, PiFM images hint at different facets whose edges and faces exhibit different amide I (1666 1/cm) signal strength. Two subsequent PiFM spectra taken on the same cage look repeatable, however, with minor variations in amide I region.
In Ajitha Cristie-David and Neil Marsh’s paper, “Evaluation of denovo-designed coiled coils as off-the-shelf components for protein assembly” (DOI: 10.1039/C7ME00012J), a compelling argument for spatially resolved PiFM is made. If we can identify favorable conditions for protein self-assembly, we may advance the future application of coiled coils in the construction of large-scale protein assemblies:
“These observations suggest that by screening a fairly sparse matrix of spacer lengths and coiled coil strengths, it should be possible to identify conditions for successful protein assembly in many cases.”
We are excited to continue this story with the researchers at the University of Michigan.