title: Optimizing bead size reduces errors in force measurements in optical traps.
abstract: Optical traps are used to measure force (F) over a wide range (0.01 to 1,000 pN). Variations in bead radius (r) hinder force precision since trap stiffness (k(trap)) varies as r3 when r is small. Prior work has shown k(trap) is maximized when r is approximately equal to the beam waist (w0), which on our instrument was ~400 nm when trapping with a 1064-nm laser. In this work, we show that by choosing r ≈w0, we improved the force precision by 2.8-fold as compared to a smaller bead (250 nm). This improvement in force precision was verified by pulling on a canonical DNA hairpin. Thus, by using an optimum bead size, one can simultaneously maximize k(trap) while minimizing errors in F.
authors: JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309, USA.
authors: Rebecca K
authors: RK
authors: Montange
authors: Matthew S
authors: MS
authors: Bull
authors: Elisabeth R
authors: ER
authors: Shanblatt
authors: Thomas T
authors: TT
authors: Perkins
mesh_terms: D001703:Biophysics / Q000379:methods*; D002138:Calibration; D004247:DNA / Q000737:chemistry*; D057446:Hydrodynamics; D007700:Kinetics; D007834:Lasers; D008027:Light; D009690:Nucleic Acid Conformation; D052898:Optical Tweezers; D055095:Optics and Photonics; D010316:Particle Size; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D004247:DNA