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Skewed brownian fluctuations in single-molecule magnetic tweezers.

ABSTRACT: Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, here we demonstrate that nearby surfaces and the non-linear elasticity of DNA can skew the distribution. Through experiment and simulations, we show that such a skewing leads to inaccurate position measurements which significantly affect the extracted DNA extension and mechanical properties, leading to up to two-fold errors in measured DNA persistence length. We develop a simple, robust and easily implemented method to correct for such mismeasurements.

SUBMITTER: Burnham DR

PROVIDER: S-EPMC4180755 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Skewed brownian fluctuations in single-molecule magnetic tweezers.

Burnham Daniel R DR De Vlaminck Iwijn I Henighan Thomas T Dekker Cees C

PloS one 20140929 9

Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, ...[more]

PMID: 25265383

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