High-Performance Image-Based Measurements of Biological Forces and Interactions in a Dual Optical Trap

AbstractOptical traps enable nanoscale manipulation of individual biomolecules while measuring molecular forces and lengths. This ability relies on the sensitive detection of optically trapped particles, typically accomplished using laser-based interferometric methods. Recently, precise and fast image-based particle tracking techniques have garnered increased interest as a potential alternative to laser-based detection, however successful integration of image-based methods into optical trapping instruments for biophysical applications and force measurements has remained elusive. Here we develop a camera-based detection platform that enables exceptionally accurate and precise measurements of biological forces and interactions in a dual optical trap. In demonstration, we stretch and unzip DNA molecules while measuring the relative distances of trapped particles from their trapping centers with sub-nanometer accuracy and precision, a performance level previously only achieved using photodiodes. We then use the DNA unzipping technique to localize bound proteins with extraordinary sub-base-pair precision, revealing how thermal DNA fluctuations allow an unzipping fork to sense and respond to a bound protein prior to a direct encounter. This work significantly advances the capabilities of image tracking in optical traps, providing a state-of-the-art detection method that is accessible, highly flexible, and broadly compatible with diverse experimental substrates and other nanometric techniques.

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Tunable optical lattices in the near-field of a few-mode nanophotonic waveguide

EPJ Web of Conferences ◽

10.1051/epjconf/201921514001 ◽

2019 ◽

Vol 215 ◽

pp. 14001

Author(s):

Christophe Pin ◽

Jean-Baptiste Jager ◽

Manon Tardif ◽

Emmanuel Picard ◽

Emmanuel Hadji ◽

...

Keyword(s):

Light Propagation ◽

Near Field ◽

Laser Wavelength ◽

Optical Traps ◽

Trapped Particles ◽

Periodic Arrays ◽

Dielectric Particles ◽

Light Coupling ◽

Scattering Force ◽

Optically Trapped

Due to the action of the scattering force, particles that are optically trapped at the surface of a waveguide are propelled in the direction of the light propagation. In this work, we demonstrate an original approach for creating tunable periodic arrays of optical traps along a few-mode silicon nanophotonic waveguide. We show how the near-field optical forces at the surface of the waveguide are periodically modulated when two guided modes with different propagation constants are simultaneously excited. The phenomenon is used to achieve stable trapping of a large number of dielectric particles or bacteria along a single waveguide. By controlling the light coupling conditions and the laser wavelength, we investigate several techniques for manipulating the trapped particles. Especially, we demonstrate that the period of the optical lattice can be finely tuned by adjusting the laser wavelength. This effect can be used to control the trap positions, and thus transport the trapped particles in both directions along the waveguide.

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Molecule-molecule and atom-molecule collisions with ultracold RbCs molecules

New Journal of Physics ◽

10.1088/1367-2630/ac3c63 ◽

2021 ◽

Author(s):

Philip David Gregory ◽

Jacob A Blackmore ◽

Matthew David Frye ◽

Luke M. Fernley ◽

Sarah L Bromley ◽

...

Keyword(s):

Ground State ◽

Optical Trap ◽

Optical Excitation ◽

Inelastic Collisions ◽

Optical Traps ◽

Fundamental Importance ◽

Ultracold Collisions ◽

Free Decay ◽

Optically Trapped ◽

Loss Rates

Abstract Understanding ultracold collisions involving molecules is of fundamental importance for current experiments, where inelastic collisions typically limit the lifetime of molecular ensembles in optical traps. Here we present a broad study of optically trapped ultracold RbCs molecules in collisions with one another, in reactive collisions with Rb atoms, and in nonreactive collisions with Cs atoms. For experiments with RbCs alone, we show that by modulating the intensity of the optical trap, such that the molecules spend 75\% of each modulation cycle in the dark, we partially suppress collisional loss of the molecules. This is evidence for optical excitation of molecule pairs mediated via sticky collisions. We find that the suppression is less effective for molecules not prepared in the spin-stretched hyperfine ground state. This may be due either to longer lifetimes for complexes or to laser-free decay pathways. For atom-molecule mixtures, RbCs+Rb and RbCs+Cs, we demonstrate that the rate of collisional loss of molecules scales linearly with the density of atoms. This indicates that, in both cases, the loss of molecules is rate-limited by two-body atom-molecule processes. For both mixtures, we measure loss rates that are below the thermally averaged universal limit.

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Steady state of overdamped particles in the non-conservative force field of a simple non-linear model of optical trap

Journal of Statistical Mechanics Theory and Experiment ◽

10.1088/1742-5468/ac3907 ◽

2021 ◽

Vol 2021 (11) ◽

pp. 113205

Author(s):

Matthieu Mangeat ◽

Thomas Guérin ◽

David S Dean

Keyword(s):

Steady State ◽

Force Field ◽

Brownian Particle ◽

Optical Trap ◽

Three Dimensional ◽

Planck Equation ◽

Steady State Probability ◽

Trapped Particles ◽

Scattering Force ◽

Optically Trapped

Abstract Optically trapped particles are often subject to a non-conservative scattering force arising from radiation pressure. In this paper, we present an exact solution for the steady state statistics of an overdamped Brownian particle subjected to a commonly used force field model for an optical trap. The model is the simplest of its kind that takes into account non-conservative forces. In particular, we present the exact results for certain marginals of the full three-dimensional steady state probability distribution, in addition to results for the toroidal probability currents that are present in the steady state, as well as for the circulation of these currents. Our analytical results are confirmed by numerical solution of the steady state Fokker–Planck equation.

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Positioning Accuracy in Holographic Optical Traps

Micromachines ◽

10.3390/mi12050559 ◽

2021 ◽

Vol 12 (5) ◽

pp. 559

Author(s):

Frederic Català-Castro ◽

Estela Martín-Badosa

Keyword(s):

Optical Tweezers ◽

Dynamic Control ◽

Optical Trap ◽

Optical Traps ◽

Spatial Light Modulators ◽

Positioning Accuracy ◽

Light Modulators ◽

Holographic Optical Tweezers ◽

The One ◽

Optically Trapped

Spatial light modulators (SLMs) have been widely used to achieve dynamic control of optical traps. Often, holographic optical tweezers have been presumed to provide nanometer or sub-nanometer positioning accuracy. It is known that some features concerning the digitalized structure of SLMs cause a loss in steering efficiency of the optical trap, but their effect on trap positioning accuracy has been scarcely analyzed. On the one hand, the SLM look-up-table, which we found to depend on laser power, produces positioning deviations when the trap is moved at the micron scale. On the other hand, phase quantization, which makes linear phase gratings become phase staircase profiles, leads to unexpected local errors in the steering angle. We have tracked optically trapped microspheres with sub-nanometer accuracy to study the effects on trap positioning, which can be as high as 2 nm in certain cases. We have also implemented a correction strategy that enabled the reduction of errors down to 0.3 nm.

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Determination of Selected Phthalates in Some Commercial Cosmetic Products by HPLC-UV

Combinatorial Chemistry & High Throughput Screening ◽

10.2174/1386207323666200630113850 ◽

2020 ◽

Vol 23 (10) ◽

pp. 1010-1022

Author(s):

Emrah Dural

Keyword(s):

High Performance ◽

Phthalate Esters ◽

High Sensitivity ◽

Hplc Method ◽

Cosmetic Products ◽

Limit Of Quantification ◽

Nail Polish ◽

Accuracy And Precision ◽

Butyl Phthalate

Aim and scope: Due to the serious toxicological risks and their widespread use, quantitative determination of phthalates in cosmetic products have importance for public health. The aim of this study was to develop a validated simple, rapid and reliable high-performance liquid chromatography (HPLC) method for the determination of phthalates which are; dimethyl phthalate (DMP), diethyl phthalate (DEP), benzyl butyl phthalate (BBP), di-n-butyl phthalate (DBP), di(2- ethylhexyl) phthalate (DEHP), in cosmetic products and to investigate these phthalate (PHT) levels in 48 cosmetic products marketing in Sivas, Turkey. Materials and Methods: Separation was achieved by a reverse-phase ACE-5 C18 column (4.6 x 250 mm, 5.0 μm). As the mobile phase, 5 mM KH2PO4 and acetonitrile were used gradiently at 1.5 ml min-1. All PHT esters were detected at 230 nm and the run time was taking 21 minutes. Results: This method showed the high sensitivity value the limit of quantification (LOQ) values for which are below 0.64 μg mL-1 of all phthalates. Method linearity was ≥0.999 (r2). Accuracy and precision values of all phthalates were calculated between (-6.5) and 6.6 (RE%) and ≤6.2 (RSD%), respectively. Average recovery was between 94.8% and 99.6%. Forty-eight samples used for both babies and adults were successfully analyzed by the developed method. Results have shown that, DMP (340.7 μg mL-1 ±323.7), DEP (1852.1 μg mL-1 ± 2192.0), and DBP (691.3 μg mL-1 ± 1378.5) were used highly in nail polish, fragrance and cream products, respectively. Conclusion: Phthalate esters, which are mostly detected in the content of fragrance, cream and nail polish products and our research in general, are DEP (1852.1 μg mL-1 ± 2192.0), DBP (691.3 μg mL-1 ± 1378.5) and DMP (340.7 μg mL-1 ±323.7), respectively. Phthalates were found in the content of all 48 cosmetic products examined, and the most detected phthalates in general average were DEP (581.7 μg mL-1 + 1405.2) with a rate of 79.2%. The unexpectedly high phthalate content in the examined cosmetic products revealed a great risk of these products on human health. The developed method is a simple, sensitive, reliable and economical alternative for the determination of phthalates in the content of cosmetic products, it can be used to identify phthalate esters in different products after some modifications.

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Recent Applications of High Performance Thin Layer Chromatography and Derivative Spectrophotometry in Pharmaceutical Analysis

Current Pharmaceutical Analysis ◽

10.2174/1573412915666190226155149 ◽

2020 ◽

Vol 16 (6) ◽

pp. 671-689

Author(s):

Marcin Gackowski ◽

Marcin Koba ◽

Katarzyna Mądra-Gackowska ◽

Piotr Kośliński ◽

Stefan Kruszewski

Keyword(s):

Thin Layer ◽

Thin Layer Chromatography ◽

Pharmaceutical Analysis ◽

High Performance ◽

Degradation Products ◽

Derivative Spectrophotometry ◽

Accuracy And Precision ◽

Post Marketing ◽

Layer Chromatography

At present, no one can imagine drug development, marketing and post-marketing without rigorous quality control at each stage. Only modern, selective, accurate and precise analytical methods for determination of active compounds, their degradation products and stability studies are able to assure the appropriate amount and purity of drugs administered every day to millions of patients all over the world. For routine control of drugs simple, economic, rapid and reliable methods are desirable. The major focus of current scrutiny is placed on high-performance thin layer chromatography and derivative spectrophotometry methods, which fulfill routine drug estimation’s expectations [1-4]. The present paper reveals state-of-the-art and possible applications of those methods in pharmaceutical analysis between 2010 and 2018. The review shows advantages of high-performance thin layer chromatography and derivative spectrophotometry, including accuracy and precision comparable to more expensive and time-consuming methods as well as additional fields of possible applications, which contribute to resolving many analytical problems in everyday laboratory practice.

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Simplified and Rapid Determination of Primaquine and 5,6-Orthoquinone Primaquine by UHPLC-MS/MS: Its Application to a Pharmacokinetic Study

Molecules ◽

10.3390/molecules26144357 ◽

2021 ◽

Vol 26 (14) ◽

pp. 4357

Author(s):

Waritda Pookmanee ◽

Siriwan Thongthip ◽

Jeeranut Tankanitlert ◽

Mathirut Mungthin ◽

Chonlaphat Sukasem ◽

...

Keyword(s):

Pharmacokinetic Study ◽

High Performance ◽

Rapid Determination ◽

Active Metabolites ◽

Chromatography Tandem Mass Spectrometry ◽

Accuracy And Precision ◽

The Matrix ◽

Liquid Chromatography Tandem Mass ◽

Isocratic Mode

The method for the determination of primaquine (PQ) and 5,6-orthoquinone primaquine (5,6-PQ), the representative marker for PQ active metabolites, via CYP2D6 in human plasma and urine has been validated. All samples were extracted using acetonitrile for protein precipitation and analyzed using the ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) system. Chromatography separation was carried out using a Hypersil GOLDTM aQ C18 column (100 × 2.1 mm, particle size 1.9 μm) with a C18 guard column (4 × 3 mm) flowed with an isocratic mode of methanol, water, and acetonitrile in an optimal ratio at 0.4 mL/min. The retention times of 5,6-PQ and PQ in plasma and urine were 0.8 and 1.6 min, respectively. The method was validated according to the guideline. The linearity of the analytes was in the range of 25–1500 ng/mL. The matrix effect of PQ and 5,6-PQ ranged from 100% to 116% and from 87% to 104% for plasma, and from 87% to 89% and from 86% to 87% for urine, respectively. The recovery of PQ and 5,6-PQ ranged from 78% to 95% and form 80% to 98% for plasma, and from 102% to from 112% to 97% to 109% for urine, respectively. The accuracy and precision of PQ and 5,6-PQ in plasma and urine were within the acceptance criteria. The samples should be kept in the freezer (−80 °C) and analyzed within 7 days due to the metabolite stability. This validated UHPLC-MS/MS method was beneficial for a pharmacokinetic study in subjects receiving PQ.

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Optimal trap velocity in a dynamic holographic optical trap using a nematic liquid crystal spatial light modulator

Journal of Optics ◽

10.1088/2040-8986/ac4b19 ◽

2022 ◽

Author(s):

Karuna Sindhu Malik ◽

Bosanta Ranjan Boruah

Keyword(s):

Liquid Crystal ◽

Nematic Liquid Crystal ◽

Spatial Light Modulator ◽

Optical Trap ◽

Optical Element ◽

Optical Traps ◽

Light Modulator ◽

Step Size ◽

Microscopic Object ◽

Optimal Velocity

Abstract A dynamic holographic optical trap uses a dynamic diffractive optical element such as a liquid crystal spatial light modulator to realize one or more optical traps with independent controls. Such holographic optical traps provide a number of flexibilities and conveniences useful in various applications. One key requirement for such a trap is the ability to move the trapped microscopic object from one point to the other with the optimal velocity. In this paper we develop a nematic liquid crystal spatial light modulator based holographic optical trap and experimentally investigate the optimal velocity feasible for trapped beads of different sizes, in such a trap. Our results show that the achievable velocity of the trapped bead is a function of size of the bead, step size, interval between two steps and power carried by the laser beam. We observe that the refresh rate of a nematic liquid crystal spatial light modulator is sufficient to achieve an optimal velocity approaching the theoretical limit in the respective holographic trap for beads with radius larger than the wavelength of light.

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