Beyond the frame rate: measuring high-frequency fluctuations with light-intensity modulation

Wong, Wesley P.; Halvorsen, Ken

doi:10.1364/ol.34.000277

Cited by 17 publications

(10 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Measured P(r) for a given trapped particle were verified to be invariant for variable exposure times in the range 6-20 ms, ensuring that there were no exposure-time induced artifacts in the shape of the measured potential. 27 In order to relate the measured potential profiles, F(r) to a net surface charge density in the system, calculations of the position dependent electrostatic free energy were carried out in COM-SOL Multiphysics using constant charge boundary conditions as previously described. 22,28 Briefly, we numerically solved the non-linear Poisson-Boltzmann (PB) equation in the geometry shown in Fig.…”

Section: Single Particle Trapping Spatial Potential Profile Measumentioning

confidence: 99%

Measured electrical charge of SiO2 in polar and nonpolar media

Kokot

Bespalova

Krishnan

2016

The Journal of Chemical Physics

View full text Add to dashboard Cite

We present measurements of the net electrical surface charge of silicon dioxide (SiO2) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase. We present measurements of the net electrical surface charge of silicon dioxide (SiO 2 ) in contact with solvents of dielectric constants between 5 and 80. Our experimental approach relies on observing the thermal motion of single silica particles confined in an electrostatic fluidic trap created by SiO 2 surfaces. We compare the experimentally measured functional form of the trapping potential with that from free energy calculations and thereby determine the net surface charge in the system. Our findings clearly demonstrate that contrary to popular perception, even in the absence of surfactants, the net electrical charge of ionizable surfaces in contact with apolar solvents can be large enough to lead to significant repulsive forces. A charge regulation model for SiO 2 surfaces with a single tunable parameter explains our measurements. This model may find general applicability in estimating the net charge of ionizable surfaces, given system parameters such as the dissociation or association constants of the ionizable groups and the pH, ionic strength, and dielectric constant of the solvent phase. Published by AIP Publishing. [http://dx

show abstract

Section: Single Particle Trapping Spatial Potential Profile Measumentioning

confidence: 99%

Measured electrical charge of SiO2 in polar and nonpolar media

Kokot

Bespalova

Krishnan

2016

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…2 Although attempts have been made to increase the spatial resolution of the magnetic tweezer using specially coated beads, 13 these attempts have thus far been incapable of the low thermal noise required of high-resolution a) Electronic mail: saleh@engineering.ucsb.edu tracking. Sensitivity to thermal noise beyond the Nyquist frequency is possible using strobed light sources; 14 however, for non-stationary processes such as motor protein stepping, light strobing cannot be used to artificially enhance the data acquisition rate. The recent introduction of high-speed cameras to particle tracking [15][16][17] has opened the door to a new field of video-based single-molecule manipulation that can obtain high spatial and temporal resolution.…”

Section: Introductionmentioning

confidence: 99%

A high-speed magnetic tweezer beyond 10,000 frames per second

Lansdorp

Tabrizi

Dittmore

et al. 2013

Review of Scientific Instruments

View full text Add to dashboard Cite

The magnetic tweezer is a single-molecule instrument that can apply a constant force to a biomolecule over a range of extensions, and is therefore an ideal tool to study biomolecules and their interactions. However, the video-based tracking inherent to most magnetic single-molecule instruments has traditionally limited the instrumental resolution to a few nanometers, above the length scale of single DNA base-pairs. Here we have introduced superluminescent diode illumination and high-speed camera detection to the magnetic tweezer, with graphics processing unit-accelerated particle tracking for high-speed analysis of video files. We have demonstrated the ability of the high-speed magnetic tweezer to resolve particle position to within 1 Å at 100 Hz, and to measure the extension of a 1566 bp DNA with 1 nm precision at 100 Hz in the presence of thermal noise.

show abstract

“…In theory the approach to accurately measure the bead variance by correction for systematic acquisition biases can be expected to work successfully up until the point where the natural frequency of the system approaches the Nyquist frequency of the camera (f Nyq , equal to one-half of the sampling frequency) (19,23). However, the limitations of this approach have not been systematically explored for MT experiments, and it is presently undocumented within which force regime this approach can be reliably applied.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Guidelines for Force Calibration through Spectral Analysis of Magnetic Tweezers Data

Velthuis

Kerssemakers

Lipfert

et al. 2010

Biophysical Journal

102

View full text Add to dashboard Cite

Single-molecule techniques are powerful tools that can be used to study the kinetics and mechanics of a variety of enzymes and their complexes. Force spectroscopy, for example, can be used to control the force applied to a single molecule and thereby facilitate the investigation of real-time nucleic acid-protein interactions. In magnetic tweezers, which offer straightforward control and compatibility with fluorescence measurements or parallel tracking modes, force-measurement typically relies on the analysis of positional fluctuations through video microscopy. Significant errors in force estimates, however, may arise from incorrect spectral analysis of the Brownian motion in the magnetic tweezers. Here we investigated physical and analytical optimization procedures that can be used to improve the range over which forces can be reliably measured. To systematically probe the limitations of magnetic tweezers spectral analysis, we have developed a magnetic tweezers simulator, whose outcome was validated with experimental data. Using this simulator, we evaluate methods to correctly perform force experiments and provide guidelines for correct force calibration under configurations that can be encountered in typical magnetic tweezers experiments.

show abstract

Beyond the frame rate: measuring high-frequency fluctuations with light-intensity modulation

Cited by 17 publications

References 20 publications

Measured electrical charge of SiO2 in polar and nonpolar media

Measured electrical charge of SiO2 in polar and nonpolar media

A high-speed magnetic tweezer beyond 10,000 frames per second

Quantitative Guidelines for Force Calibration through Spectral Analysis of Magnetic Tweezers Data

Contact Info

Product

Resources

About