One of the greatest challenges in molecular biophysics is developing single molecule assays. Here we describe a new strategy for forming linkages between proteins of interest and an object such as a bead appropriate for use in the optical trap. In collaboration with Prof. Angela Belcher's lab, we have developed a new strategy for forming these linkages, based on the M13 bacteriophage. Our strategy uses genetic engineering to form the linkages, i.e., proteins of interest are covalently displayed on phage capsid proteins via genetic modification of the M13 genome. As a result, we exploit the natural assembly process of bacteriophages in E. coli to construct stand-alone tethers. We have characterized the mechanical properties of this tether and found that it has excellent properties: (1) Optimal length (~1um) for applying horizontal loads. In particular, it is long enough to calibrate and mitigate force correction terms, yet short enough to properly communicate mechanical transitions; (2) Stiffness 3X that of dsDNA; (3) Strength to withstand forces above 60pN. This work has been published in PNAS, see Khalil et al.

See: Khalil et.al., PNAS 2007