Counter-propagating dual-trap optical tweezers based on linear momentum conservation

Ribezzi-Crivellari, Marco; Huguet, Josep Maria; Ritort, Fèlix

doi:10.1063/1.4799289

Cited by 17 publications

(20 citation statements)

References 31 publications

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“…Measurements were performed with a highly stable miniaturized laser tweezers in the dual-trap mode (32). This instrument directly measures forces by linear momentum conservation.…”

Section: Methodsmentioning

confidence: 99%

“…The theory discussed so far has been put to test in a series of pulling experiments performed in a recently developed dual-trap optical tweezers setup that directly measures force in each trap (31,32). The setup can move the two optical traps independently and measure their relative position with subnanometer accuracy, giving direct access to both W and W′.…”

Section: Pulling On Dsdnamentioning

confidence: 99%

See 1 more Smart Citation

Free-energy inference from partial work measurements in small systems

Ribezzi-Crivellari¹,

Ritort²

2014

Proc. Natl. Acad. Sci. U.S.A.

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Fluctuation relations (FRs) are among the few existing general results in nonequilibrium systems. Their verification requires the measurement of the total work performed on a system. Nevertheless in many cases only a partial measurement of the work is possible. Here we consider FRs in dual-trap optical tweezers where two different forces (one per trap) are measured. With this setup we perform pulling experiments on single molecules by moving one trap relative to the other. We demonstrate that work should be measured using the force exerted by the trap that is moved. The force that is measured in the trap at rest fails to provide the full dissipation in the system, leading to a (incorrect) work definition that does not satisfy the FR. The implications to single-molecule experiments and free-energy measurements are discussed. In the case of symmetric setups a second work definition, based on differential force measurements, is introduced. This definition is best suited to measure free energies as it shows faster convergence of estimators. We discuss measurements using the (incorrect) work definition as an example of partial work measurement. We show how to infer the full work distribution from the partial one via the FR. The inference process does also yield quantitative information, e.g., the hydrodynamic drag on the dumbbell. Results are also obtained for asymmetric dualtrap setups. We suggest that this kind of inference could represent a previously unidentified and general application of FRs to extract information about irreversible processes in small systems.statistical mechanics | biophysics | fluctuation theorems F luctuation relations (FRs) are mathematical equations connecting non equilibrium work measurements to equilibrium free-energy differences. FRs, such as the Jarzynski equality (JE) or the Crooks fluctuation relation (CFR), have become a valuable tool in single-molecule biophysics where they are used to measure folding free energies from irreversible pulling experiments (1, 2). Such measurements have been carried out with laser optical tweezers on different nucleic acid structures such as hairpins (3-6), G quadruplexes (7,8), and proteins (9-12) and with atomic force microscopes on proteins (13) and bimolecular complexes (14). An important issue regarding FRs is the correct definition of work, which rests on the correct identification of configurational variables and control parameters. In the singletrap optical tweezers configuration this issue has been thoroughly discussed (17)(18)(19).The situation of how to correctly measure work in small systems becomes subtle when there are different forces applied to the system. In this case theory gives the prescription to correctly define the work (W Γ ) for a given trajectory (Γ): Integrate the generalized force (f λ ) (conjugated to the control parameter, λ) over λ along Γ, W Γ = R Γ f λ dλ. However, in some cases one cannot measure the proper generalized force or has limited experimental access to partial sources of the entropy production, leading to wha...

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“…Measurements were performed with a highly stable miniaturized laser tweezers in the dual-trap mode (32). This instrument directly measures forces by linear momentum conservation.…”

Section: Methodsmentioning

confidence: 99%

Section: Pulling On Dsdnamentioning

confidence: 99%

Free-energy inference from partial work measurements in small systems

Ribezzi-Crivellari¹,

Ritort²

2014

Proc. Natl. Acad. Sci. U.S.A.

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“…64 Constant-force dumbbell assays may also be implemented using counter-propagating laser beams, which allow for shorter than usual DNA handles if so desired. 65,66 While the emphasis of this review is on the use of optical tweezers for unfolding individual molecules alternative techniques deserve mentioning and in some cases be more beneficial for particular applications.…”

Section: Optical Tweezersmentioning

confidence: 99%

−1 Programmed Ribosomal Frameshifting as a Force-Dependent Process

Visscher

2016

Progress in Molecular Biology and Translational Science

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-1 Programmed ribosomal frameshifting is a translational recoding event in which ribosomes slip backward along messenger RNA presumably due to increased tension disrupting the codon-anticodon interaction at the ribosome's coding site. Single-molecule physical methods and recent experiments characterizing the physical properties of mRNA's slippery sequence as well as the mechanical stability of downstream mRNA structure motifs that give rise to frameshifting are discussed. Progress in technology, experimental assays, and data analysis methods hold promise for accurate physical modeling and quantitative understanding of -1 programmed ribosomal frameshifting.

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“…Several implementations of such setups exist. The most commonly used implementation of this method consists of two opposite-travelling trapping beams focused into the same focal point by a pair of lenses [18]. This arrangement permits to reduce the required NA for successful trapping and thus, increase the working distance of the focusing optics [17].…”

Section: Introductionmentioning

confidence: 99%

Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer

Galinskiy¹,

Isaksson²,

Rebolledo-Salgado³

et al. 2015

Opt. Express

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We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counterpropagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets.

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Counter-propagating dual-trap optical tweezers based on linear momentum conservation

Cited by 17 publications

References 31 publications

Free-energy inference from partial work measurements in small systems

Free-energy inference from partial work measurements in small systems

−1 Programmed Ribosomal Frameshifting as a Force-Dependent Process

Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer

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