  Methods for patterning biomolecules on a substrate at the single molecule
level have been studied as a route to sensors with single-molecular sensitivity
or as a way to probe biological phenomena at the single-molecule level.
However, the arrangement and orientation of single biomolecules on substrates
has been less investigated. Here, we examined the arrangement and orientation
of two rod-like coiled-coil proteins, cortexillin and tropomyosin, around
patterned gold nanostructures. The high aspect ratio of the coiled coils made
it possible to study their orientations and to pursue a strategy of protein
orientation via two-point attachment. The proteins were anchored to the
surfaces using thiol groups, and the number of cysteine residues in tropomyosin
was varied to test how this variation affected the structure and arrangement of
the surface-attached proteins. Molecular dynamics studies were used to
interpret the observed positional distributions. Based on initial studies of
protein attachment to gold post structures, two 31-nm-long tropomyosin
molecules were aligned between the two sidewalls of a trench with a width of 68
nm. Because the approach presented in this study uses one of twenty natural
amino acids, this method provides a convenient way to pattern biomolecules on
substrates using standard chemistry.
