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optical tweezers

Imogen Sparkes, Rhiannon R White, Benjamin Coles, Stanley W Botchway, Andy Ward
Optical tweezers have been used to trap and micromanipulate several biological specimens ranging from DNA, macromolecules, organelles to single celled organisms. Using a combination of the refraction and scattering of laser light from a focused laser beam, refractile objects are physically captured and can be moved within the surrounding media. The technique is routinely used to determine biophysical properties such as the forces exerted by motor proteins. Here, we describe how optical tweezers combined with total internal reflection fluorescence (TIRF) microscopy can be used to assess physical interactions between organelles, more specifically the ER and Golgi bodies in plant cells...
2018: Methods in Molecular Biology
Z L Liu, Y X Liu, Y Tang, N Zhang, F P Wu, B Zhang
A double-tapered optical fiber tweezers (DOFTs) was fabricated by a chemical etching called interfacial layer etching. In this method, the second taper angle (STA) of DOFTs can be controlled easily by the interfacial layer etching time. Application of the DOFTs to the optical trapping of the yeast cells was presented. Effects of the STA on the axile trapping efficiency and the trapping position were investigated experimentally and theoretically. The experimental results are good agreement with the theoretical ones...
September 18, 2017: Optics Express
F G Mitri
This work demonstrates the generation of auto-bending cylindrical/tubular Bessel-Gauss bottle beams in homogeneous two-dimensional (2D) space. The corresponding wave fields flow through a two-dimensional curved trajectory leaving a singularity hollow central region, exhibiting the characteristic of circumventing obstacles. Scalar and vector fields are derived based on the angular spectrum decomposition method, the Helmholtz equation, the Lorenz gauge condition, and Maxwell's equations. The profile and area of the 2D bottle beams, together with the location of the autofocusing spots, are controlled by the intrinsic parameters of the illuminating waves and polarizations of the vector potential forming the incident fields...
July 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Chaoyang Ti, Minh-Tri Ho-Thanh, Qi Wen, Yuxiang Liu
Position detection with high accuracy is crucial for force calibration of optical trapping systems. Most existing position detection methods require high-numerical-aperture objective lenses, which are bulky, expensive, and difficult to miniaturize. Here, we report an affordable objective-lens-free, fiber-based position detection scheme with 2 nm spatial resolution and 150 MHz bandwidth. This fiber based detection mechanism enables simultaneous trapping and force measurements in a compact fiber optical tweezers system...
October 13, 2017: Scientific Reports
Nyha Hameed, Ali Nouho Ali, Fadi I Baida
In this paper, we propose and numerically simulate a novel optical trapping process based on the enhancement and the confinement of both magnetic and electric near-fields by using gold Diabolo Antenna (DA). The later was recently proposed to generate huge magnetic near-field when illuminated by linearly polarized wave along its axis. Numerical 3D - FDTD simulation results demonstrate the high confinement of the electromagnetic field in the vicinity of the DA. This enhancement is then exploited for the trapping of nano-particles (NP) as small as 30 nm radius...
October 9, 2017: Scientific Reports
Teresa Naranjo, Fernando Cerrón, Belén Nieto-Ortega, Alfonso Latorre, Álvaro Somoza, Borja Ibarra, Emilio M Pérez
Decades after the birth of supramolecular chemistry, there are many techniques to measure noncovalent interactions, such as hydrogen bonding, under equilibrium conditions. As ensembles of molecules rapidly lose coherence, we cannot extrapolate bulk data to single-molecule events under non-equilibrium conditions, more relevant to the dynamics of biological systems. We present a new method that exploits the high force resolution of optical tweezers to measure at the single molecule level the mechanical strength of a hydrogen bonded host-guest pair out of equilibrium and under near-physiological conditions...
September 1, 2017: Chemical Science
Raphaël Clément, Benoît Dehapiot, Claudio Collinet, Thomas Lecuit, Pierre-François Lenne
Tissue morphogenesis relies on the production of active cellular forces. Understanding how such forces are mechanically converted into cell shape changes is essential to our understanding of morphogenesis. Here, we use myosin II pulsatile activity during Drosophila embryogenesis to study how transient forces generate irreversible cell shape changes. Analyzing the dynamics of junction shortening and elongation resulting from myosin II pulses, we find that long pulses yield less reversible deformations, typically a signature of dissipative mechanics...
October 4, 2017: Current Biology: CB
Kyle Gorkowski, Neil M Donahue, Ryan C Sullivan
We demonstrate the first capture and analysis of secondary organic aerosol (SOA) on a droplet suspended in an aerosol optical tweezers (AOT). We examine three initial chemical systems of aqueous NaCl, aqueous glycerol, and squalane at ∼75% relative humidity. For each system we added α-pinene SOA-generated directly in the AOT chamber-to the trapped droplet. The resulting morphology was always observed to be a core of the original droplet phase surrounded by a shell of the added SOA. We also observed a stable emulsion of SOA particles when added to an aqueous NaCl core phase, in addition to the shell of SOA...
October 18, 2017: Environmental Science & Technology
Avin Ramaiya, Basudev Roy, Michael Bugiel, Erik Schäffer
Cytoskeletal motors drive many essential cellular processes. For example, kinesin-1 transports cargo in a step-wise manner along microtubules. To resolve rotations during stepping, we used optical tweezers combined with an optical microprotractor and torsion balance using highly birefringent microspheres to directly and simultaneously measure the translocation, rotation, force, and torque generated by individual kinesin-1 motors. While, at low adenosine 5'-triphosphate (ATP) concentrations, motors did not generate torque, we found that motors translocating along microtubules at saturating ATP concentrations rotated unidirectionally, producing significant torque on the probes...
September 25, 2017: Proceedings of the National Academy of Sciences of the United States of America
Omri Malik, Hadeel Khamis, Sergei Rudnizky, Ailie Marx, Ariel Kaplan
Reverse transcriptase (RT) catalyzes the conversion of the viral RNA into an integration-competent double-stranded DNA, with a variety of enzymatic activities that include the ability to displace a non-template strand concomitantly with polymerization. Here, using high-resolution optical tweezers to follow the activity of the murine leukemia Virus RT, we show that strand-displacement polymerization is frequently interrupted. Abundant pauses are modulated by the strength of the DNA duplex ∼8 bp ahead, indicating the existence of uncharacterized RT/DNA interactions, and correspond to backtracking of the enzyme, whose recovery is also modulated by the duplex strength...
September 29, 2017: Nucleic Acids Research
Jacob W Black, Maria Kamenetska, Ziad Ganim
Observation at the single molecule level has been a revolutionary tool for molecular biophysics and materials science, but single molecule studies of solution-phase chemistry are less widespread. In this work we develop an experimental platform for solution-phase single molecule force spectroscopy in organic solvents. This optical-tweezer-based platform was designed for broad chemical applicability and utilizes optically trapped core-shell microspheres, synthetic polymer tethers, and click chemistry linkages formed in situ...
October 17, 2017: Nano Letters
Qiangzhou Rong, Yi Zhou, Xunli Yin, Zhihua Shao, Xueguang Qiao
Optical manipulation using optical micro- and nano-fibers has shown potential for controlling bacterial activities such as E. coli trapping, propelling, and binding. Most of these manipulations have been performed using the propagation of the fundamental mode through the fiber. However, along the maximum mode-intensity axis, the higher-order modes have longer evanescent field extensions and larger field amplitudes at the fiber waist than the fundamental mode, opening up new possibilities for manipulating E...
September 1, 2017: Biomedical Optics Express
Thomas F Dixon, Lachlan W Russell, Ana Andres-Arroyo, Peter J Reece
We experimentally investigate the influence of geometric aberrations in optical tweezers using back focal plane interferometry. We found that the introduction of coma aberrations causes significant modification to the Brownian motion of the trapped particle, producing an apparent cross-coupling between the in-plane aberrated axis and the weaker propagation axis. This coupling is evidenced by the emergence of a second dominant low frequency Lorentzian feature in the position power spectral density. The effect on Brownian motion was confirmed using a secondary unaberrated probe beam, ruling out the possibility of systematic optical effects related to the detection system...
August 1, 2017: Optics Letters
L A Shaw, Robert M Panas, C M Spadaccini, J B Hopkins
The aim of this Letter is to introduce a new optical tweezers approach, called scanning holographic optical tweezers (SHOT), which drastically increases the working area (WA) of the holographic-optical tweezers (HOT) approach, while maintaining tightly focused laser traps. A 12-fold increase in the WA is demonstrated. The SHOT approach achieves its utility by combining the large WA of the scanning optical tweezers (SOT) approach with the flexibility of the HOT approach for simultaneously moving differently structured optical traps in and out of the focal plane...
August 1, 2017: Optics Letters
Ali Akbar Khorshad, S Nader S Reihani, Mohammad Taghi Tavassoly
Optical tweezers have proven to be indispensable tools for pico-Newton range force spectroscopy. A quadrant photodiode (QPD) positioned at the back focal plane of an optical tweezers' condenser is commonly used for locating the trapped object. In this Letter, for the first time, to the best of our knowledge, we introduce a moiré pattern-based detection method for optical tweezers. We show, both theoretically and experimentally, that this detection method could provide considerably better position sensitivity compared to the commonly used detection systems...
September 1, 2017: Optics Letters
Tatsuya Shoji, Ayaka Mototsuji, Armandas Balčytis, Denver Linklater, Saulius Juodkazis, Yasuyuki Tsuboi
Nowadays, optical tweezers have undergone explosive developments in accordance with a great progress of lasers. In the last decade, a breakthrough brought optical tweezers into the nano-world, overcoming the diffraction limit. This is called plasmonic optical tweezers (POT). POT are powerful tools used to manipulate nanomaterials. However, POT has several practical issues that need to be overcome. First, it is rather difficult to fabricate plasmonic nanogap structures regularly and rapidly at low cost. Second, in many cases, POT suffers from thermal effects (Marangoni convection and thermophoresis)...
September 26, 2017: Scientific Reports
Anna Bezryadina, Jinxing Li, Junxiang Zhao, Alefia Kothambawala, Joseph Ponsetto, Eric Huang, Joseph Wang, Zhaowei Liu
Localized plasmonic structured illumination microscopy (LPSIM) is a recently developed super resolution technique that demonstrates immense potential via arrays of localized plasmonic antennas. Microlens microscopy represents another distinct approach for improving resolution by introducing a spherical lens with a large refractive index to boost the effective numerical aperture of the imaging system. In this paper, we bridge together the LPSIM and optically trapped spherical microlenses, for the first time, to demonstrate a new super resolution technique for surface imaging...
October 12, 2017: Nanoscale
Loïc Anderegg, Benjamin L Augenbraun, Eunmi Chae, Boerge Hemmerling, Nicholas R Hutzler, Aakash Ravi, Alejandra Collopy, Jun Ye, Wolfgang Ketterle, John M Doyle
We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and either rf modulated or dc magnetic fields. The rf magneto-optical trap (MOT) confines 1.0(3)×10^{5} CaF molecules at a density of 7(3)×10^{6}  cm^{-3}, which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of 340(20)  μK are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation...
September 8, 2017: Physical Review Letters
Yang Zhao, Amr A E Saleh, Marie Anne van de Haar, Brian Baum, Justin A Briggs, Alice Lay, Olivia A Reyes-Becerra, Jennifer A Dionne
Circularly polarized light (CPL) exerts a force of different magnitude on left- and right-handed enantiomers, an effect that could be exploited for chiral resolution of chemical compounds as well as controlled assembly of chiral nanostructures. However, enantioselective optical forces are challenging to control and quantify because their magnitude is extremely small (sub-piconewton) and varies in space with sub-micrometre resolution. Here, we report a technique to both strengthen and visualize these forces, using a chiral atomic force microscope probe coupled to a plasmonic optical tweezer...
September 25, 2017: Nature Nanotechnology
Kalpesh D Mahajan, Yixiao Cui, C Jenny Dorcéna, Nathan F Bouxsien, George D Bachand, Jeffrey J Chalmers, Jessica O Winter
BACKGROUND: The microtubule (MT)-kinesin system has been extensively studied because of its role in cellular processes, as well as its potential use for controllably transporting objects at the nanoscale. Thus, there is substantial interest in methods to evaluate MT properties, including bending radius and the binding energy of kinesin motor proteins to MT tracks. Current methods to identify these properties include optical tweezers, microfluidic devices, and magnetic fields. METHODS: Here, the use of magnetic quantum dots (i...
September 23, 2017: Biotechnology Journal
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