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optical tweezers

Joana S Paiva, Pedro A S Jorge, Carla C Rosa, João P S Cunha
BACKGROUND: The tip of an optical fiber has been considered an attractive platform in Biology. The simple cleaved end of an optical fiber can be machined, patterned and/or functionalized, acquiring unique properties enabling the exploitation of novel optical phenomena. Prompted by the constant need to measure and manipulate nanoparticles, the invention of the Scanning Near-Field Optical Microscopy (SNOM) triggered the optimization and development of novel fiber tip microfabrication methods...
February 15, 2018: Biochimica et Biophysica Acta
Shuya Ishii, Masataka Kawai, Shin'ichi Ishiwata, Madoka Suzuki
The interaction between actin filaments and myosin molecular motors is a power source of a variety of cellular functions including cell division, cell motility, and muscular contraction. In vitro motility assay examines actin filaments interacting with myosin molecules that are adhered to a substrate (e.g., glass surface). This assay has been the standard method of studying the molecular mechanisms of contraction under an optical microscope. While the force generation has been measured through an optically trapped bead to which an actin filament is attached, a force vector vertical to the glass surface has been largely ignored with the in vitro motility assay...
2018: PloS One
Xiaoyan Gao, Chen Cai, Jiabi Ma, Yunhong Zhang
Repartitioning of semi-volatile organic compounds (SVOCs) between particles is an important process to understand the particle growth and shrinkage in the atmosphere environment. Here, by using optical tweezers coupled with cavity-enhanced Raman spectroscopy, we report the repartitioning of glycerol between a levitated glycerol/NaNO3/H2O droplet and surrounding glycerol/NaNO3/H2O droplets deposited on the inner wall of a chamber with different organic to inorganic molar ratios (OIRs). For the high OIR with 3 : 1, no NaNO3 crystallization occurs both for levitated and deposited droplets in the whole relative humidity (RH) range, the radius of the levitated droplet decreases slowly due to the evaporation of glycerol from the levitated droplet at constant RHs...
January 2018: Royal Society Open Science
Xu-Zhen Gao, Yue Pan, Meng-Dan Zhao, Guan-Lin Zhang, Yu Zhang, Chenghou Tu, Yongnan Li, Hui-Tian Wang
We introduce a general fractal lattice growth model, significantly expanding the application scope of the fractal in the realm of optics. This model can be applied to construct various kinds of fractal "lattices" and then to achieve the design of a great diversity of fractal vector optical fields (F-VOFs) combinating with various "bases". We also experimentally generate the F-VOFs and explore their universal focusing behaviors. Multiple focal spots can be flexibly enginnered, and the optical tweezers experiment validates the simulated tight focusing fields, which means that this model allows the diversity of the focal patterns to flexibly trap and manipulate micrometer-sized particles...
January 22, 2018: Optics Express
Georgia Anastasiadi, Mark Leonard, Lynn Paterson, William N Macpherson
Optical tweezing is a non-invasive technique that can enable a variety of single cell experiments; however, it tends to be based on a high numerical aperture (NA) microscope objective to both deliver the tweezing laser light and image the sample. This introduces restrictions in system flexibility when both trapping and imaging. Here, we demonstrate a novel, high NA tweezing system based on micro-machined multicore optical fibers. Using the machined, multicore fiber tweezer, cells are optically manipulated under a variety of microscopes, without requiring a high NA objective lens...
February 5, 2018: Optics Express
Jeffrey E Melzer, Euan McLeod
Optical tweezers are a non-contact method of 3D positioning applicable to the fields of micro- and nano-manipulation and assembly, among others. In these applications, the ability to manipulate particles over relatively long distances at high speed is essential in determining overall process efficiency and throughput. In order to maximize manipulation speeds, it is necessary to increase the trapping laser power, which is often accompanied by undesirable heating effects due to material absorption. As such, the majority of previous studies focus primarily on trapping large dielectric microspheres using slow movement speeds at low laser powers, over relatively short translation distances...
February 5, 2018: ACS Nano
Pedro Almendarez-Rangel, Beatriz Morales-Cruzado, Erick Sarmiento-Gómez, Francisco G Pérez-Gutiérrez
Obtaining trap stiffness and calibration of the position detection system is the basis of a force measurement using optical tweezers. Both calibration quantities can be calculated using several experimental methods available in the literature. In most cases, stiffness determination and detection system calibration are performed separately, often requiring procedures in very different conditions, and thus confidence of calibration methods is not assured due to possible changes in the environment. In this work, a new method to simultaneously obtain both the detection system calibration and trap stiffness is presented...
February 1, 2018: Applied Optics
Michael Bugiel, Aniruddha Mitra, Salvatore Girardo, Stefan Diez, Erik Schäffer
Three-dimensional (3D) nanometer tracking of single biomolecules provides important information about their biological function. However, existing microscopy approaches often have only limited spatial or temporal precision and do not allow the application of defined loads. Here, we developed and applied a high-precision 3D-optical-tweezers force clamp to track in vitro the 3D motion of single kinesin-1 motor proteins along microtubules. To provide the motors with unimpeded access to the whole microtubule lattice, we mounted the microtubules on topographic surface features generated by UV-nanoimprint lithography...
January 30, 2018: Nano Letters
Deyu Zhao, Siyun Liu, Ying Gao
Compared to conventional ensemble methods, studying macromolecules at single-molecule level can reveal extraordinary clear and even surprising views for a biological reaction. In the past 20 years, single-molecule techniques have been undergoing a very rapid development, and these cutting edge technologies have revolutionized the biological research by facilitating single-molecule manipulation and detection. Here we give a brief review about these advanced techniques, including optical tweezers, magnetic tweezers, atomic force microscopy (AFM), hydrodynamic flow-stretching assay, and single-molecule fluorescence resonance energy transfer (smFRET)...
January 25, 2018: Acta Biochimica et Biophysica Sinica
Xin Lou, Nan Yu, Rui Liu, Ke Chen, Mingcheng Yang
The effects of light on colloidal particles in solution are multiple, including transfer of photonic linear/angular momentum and heating of the particles or their surroundings. The temperature increase around colloidal particles due to light heating can drive a thermoosmotic flow along a nearby boundary wall, which significantly influences the motion of the particles. Here we perform mesoscopic dynamics simulations to study two typical scenarios, where thermoosmosis is critical. In the first scenario, we consider a light-absorbing colloidal particle heated by uniform illumination...
January 25, 2018: Soft Matter
Chengyu Li, Di Cao, Chu-Bo Qi, Ya-Feng Kang, Chong-Yang Song, Dang-Dang Xu, Bei Zheng, Dai-Wen Pang, Hong-Wu Tang
Establishment of a stable analytical methodology with high-quality results is an urgent need for screening cancer biomarkers in early diagnosis of cancer. In this study, we incorporate holographic optical tweezers with upconversion luminescence encoding to design an imageable suspension array, and apply it to conduct the detection of two liver cancer related biomarkers, carcinoembryonic antigen and alpha fetal protein. This bead-based assay is actualized by forming a bead array with holographic optical tweezers and synchronously exciting the upconversion luminescence of corresponding trapped complex beads fabricated with a simple one-step sandwich immunological recognition...
January 24, 2018: Analytical Chemistry
Maurizio Righini, Antony Lee, Cristhian Cañari-Chumpitaz, Troy Lionberger, Ronen Gabizon, Yves Coello, Ignacio Tinoco, Carlos Bustamante
In recent years, highly stable optical tweezers systems have enabled the characterization of the dynamics of molecular motors at very high resolution. However, the motion of many motors with angstrom-scale dynamics cannot be consistently resolved due to poor signal-to-noise ratio. Using an acousto-optic deflector to generate a "time-shared" dual-optical trap, we decreased low-frequency noise by more than one order of magnitude compared with conventional dual-trap optical tweezers. Using this instrument, we implemented a protocol that synthesizes single base-pair trajectories, which are used to test a Large State Space Hidden Markov Model algorithm to recover their individual steps...
January 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
L Oliveira, M S Rocha
In the present work we have gone a step forward in the understanding of the DNA-cisplatin interaction, investigating the role of the ionic strength on the complexes formation. To achieve this task, we use optical tweezers to perform force spectroscopy on the DNA-cisplatin complexes, determining their mechanical parameters as a function of the drug concentration in the sample for three different buffers. From such measurements, we determine the binding parameters and study their behavior as a function of the ionic strength...
September 2017: Physical Review. E
Wenxia Lin, Jianbing Ma, Daguan Nong, Chunhua Xu, Bo Zhang, Jinghua Li, Qi Jia, Shuoxing Dou, Fangfu Ye, Xuguang Xi, Ying Lu, Ming Li
Single-molecule Förster resonance energy transfer is widely applied to study helicases by detecting distance changes between a pair of dyes anchored to overhangs of a forked DNA. However, it has been lacking single-base pair (1-bp) resolution required for revealing stepping kinetics of helicases. We designed a nanotensioner in which a short DNA is bent to exert force on the overhangs, just as in optical or magnetic tweezers. The strategy improved the resolution of Förster resonance energy transfer to 0.5 bp, high enough to uncover differences in DNA unwinding by yeast Pif1 and E...
September 29, 2017: Physical Review Letters
Márcio Santos Rocha, Ingeborg M Storm, Raniella Falchetto Bazoni, Ésio Bessa Ramos, Armando Hernandez-Garcia, Martien A Cohen Stuart, Frans Leermakers, Renko de Vries
As a model system to study the elasticity of bottle-brush polymers, we here introduce self-assembled DNA bottle brushes, consisting of a DNA main chain that can be very long and still of precisely defined length, and precisely monodisperse polypeptide side chains that are physically bound to the DNA main chains. Polypeptide side chains have a diblock architecture, where one block is a small archaeal nucleoid protein Sso7d that strongly binds to DNA. The other block is a net neutral, hydrophilic random coil polypeptide with a length of exactly 798 amino acids...
January 9, 2018: Macromolecules
Allan Raudsepp, Lisa M Kent, Simon B Hall, Martin A K Williams
The force-extension behaviour of synthesized double-stranded DNAs (dsDNAs) designed to have 2.1% or 6.6% of the thyamine bases alkyne functionalized was studied using near infrared (NIR) optical tweezers. Measurements were carried out on substrates with and without flurophores covalently attached to the alkyne moiety over an extended force range (F=0-70 pN) and results were compared to those obtained from an unmodified control. In accordance with earlier work [1] (measured over a force range F=0-5 pN), the force-extension of the dsDNA containing 2...
January 12, 2018: Biochemical and Biophysical Research Communications
Iris Elvira, Juan F Muñoz-Martínez, Álvaro Barroso, Cornelia Denz, José B Ramiro, Angel García-Cabañes, Fernando Agulló-López, Mercedes Carrascosa
Optical tools for manipulation and trapping of micro- and nano-objects are a fundamental issue for many applications in nano- and biotechnology. This work reports on the use of one such method, known as photovoltaic optoelectronics tweezers, to orientate and organize cylindrical microcrystals, specifically elongated zeolite L, on the surface of Fe-doped LiNbO3 crystal plates. Patterns of aligned zeolites have been achieved through the forces and torques generated by the bulk photovoltaic effect. The alignment patterns with zeolites parallel or perpendicular to the substrate surface are highly dependent on the features of light distribution and crystal configuration...
January 1, 2018: Optics Letters
Dedy Septiadi, Federica Crippa, Thomas Lee Moore, Barbara Rothen-Rutishauser, Alke Petri-Fink
Progress in the field of nanoparticles has enabled the rapid development of multiple products and technologies; however, some nanoparticles can pose both a threat to the environment and human health. To enable their safe implementation, a comprehensive knowledge of nanoparticles and their biological interactions is needed. In vitro and in vivo toxicity tests have been considered the gold standard to evaluate nanoparticle safety, but it is becoming necessary to understand the impact of nanosystems on cell mechanics...
January 9, 2018: Advanced Materials
Coline Prévost, Feng-Ching Tsai, Patricia Bassereau, Mijo Simunovic
The reshaping of the cell membrane is an integral part of many cellular phenomena, such as endocytosis, trafficking, the formation of filopodia, etc. Many different proteins associate with curved membranes because of their ability to sense or induce membrane curvature. Typically, these processes involve a multitude of proteins making them too complex to study quantitatively in the cell. We describe a protocol to reconstitute a curved membrane in vitro, mimicking a curved cellular structure, such as the endocytic neck...
December 7, 2017: Journal of Visualized Experiments: JoVE
Prakash Shrestha, Yunxi Cui, Jia Wei, Sagun Jonchhe, Hanbin Mao
Due to the fast diffusion, small molecules such as hydronium ions (H3O+) are expected to be homogeneously distributed, even close to the site-of-origin. Given the importance of H3O+ in numerous processes, it is surprising that H3O+ concentration ([H3O+]) is yet to be profiled near its generation site with nanometer resolution. Here, we innovated a single-molecule method to probe [H3O+] in nanometer proximity of individual alkaline phosphatases. We designed a mechanophore with cytosine(C)-C mismatch pairs in a DNA hairpin...
December 29, 2017: Analytical Chemistry
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