title: Single M13 bacteriophage tethering and stretching.
abstract: The ability to present biomolecules on the highly organized structure of M13 filamentous bacteriophage is a unique advantage. Where previously this viral template was shown to direct the orientation and nucleation of nanocrystals and materials, here we apply it in the context of single-molecule (SM) biophysics. Genetically engineered constructs were used to display different reactive species at each of the filament ends and along the major capsid, and the resulting hetero-functional particles were shown to consistently tether microscopic beads in solution. With this system, we report the development of a SM assay based on M13 bacteriophage. We also report the quantitative characterization of the biopolymer's elasticity by using an optical trap with nanometer-scale position resolution. Expanding the fluctuating rod limit of the wormlike chain to incorporate enthalpic polymer stretching yielded a model capable of accurately capturing the full range of extensions. Fits of the force-extension measurements gave a mean persistence length of approximately 1,265 nm, lending SM support for a shorter filamentous bacteriophage persistence length than previously thought. Furthermore, a predicted stretching modulus roughly two times that of dsDNA, coupled with the system's linkage versatility and load-bearing capability, makes the M13 template an attractive candidate for use in tethered bead architectures.
authors.affiliation: Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Ahmad S
authors.initials: AS
authors.lastname: Khalil
authors.forename: Jorge M
authors.initials: JM
authors.lastname: Ferrer
authors.forename: Ricardo R
authors.initials: RR
authors.lastname: Brau
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Kottmann
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Noren
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Lang
authors.forename: Angela M
authors.initials: AM
authors.lastname: Belcher
mesh_terms: D017104:Bacteriophage M13 / Q000378:metabolism*; D001696:Biomechanical Phenomena; D004247:DNA / Q000378:metabolism; D008954:Models, Biological
chemical_list: D004247:DNA