Passive all-optical force clamp for high-resolution laser trapping

Phys Rev Lett. 2005 Nov 11;95(20):208102. doi: 10.1103/PhysRevLett.95.208102. Epub 2005 Nov 8.

Abstract

Optical traps are useful for studying the effects of forces on single molecules. Feedback-based force clamps are often used to maintain a constant load, but the response time of the feedback limits bandwidth and can introduce instability. We developed a novel force clamp that operates without feedback, taking advantage of the anharmonic region of the trapping potential where the differential stiffness vanishes. We demonstrate the utility of such a force clamp by measuring the unfolding of DNA hairpins and the effect of trap stiffness on opening distance and transition rates.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Avidin / chemistry
  • Biotin / chemistry
  • DNA / chemistry*
  • Digoxigenin / chemistry
  • Lasers*
  • Microspheres
  • Nucleic Acid Conformation*
  • Optics and Photonics
  • Stress, Mechanical

Substances

  • Avidin
  • Biotin
  • DNA
  • Digoxigenin