title: Accurate measurement of force and displacement with optical tweezers using DNA molecules as metrology standards.
abstract: Optical tweezers facilitate measurement of piconewton-level forces and nanometer-level displacements and have broad applications in biophysics and soft matter physics research. We have shown previously that DNA molecules can be used as metrology standards to define such measurements. Force-extension measurements on two DNA molecules of different lengths can be used to determine four necessary measurement parameters. Here, we show that the accuracy of determining these parameters can be improved by more than 7-fold by incorporating measurements of the DNA overstretching transition and using a multi-step data analysis procedure. This method results in very robust and precise fitting of DNA force-extension measurements to the worm-like chain model. We verify the accuracy through independent measurements of DNA stretching, DNA unzipping, and microsphere contact forces.
authors.affiliation: Department of Physics, University of California , San Diego, Mail Code 0379, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Damian
authors.initials: D
authors.lastname: delToro
authors.affiliation: Department of Physics, University of California , San Diego, Mail Code 0379, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Smith