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Phys Rev Lett. 2005 Nov 11;95(20):208102. Epub 2005 Nov 8.

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

Author information

1
Department of Applied Physics, Stanford University, Stanford, California 94305-5020, USA.

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.

PMID:
16384102
PMCID:
PMC1357091
DOI:
10.1103/PhysRevLett.95.208102
[Indexed for MEDLINE]
Free PMC Article

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