Showing papers on "Optical tweezers published in 1993"
TL;DR: It is found that kinesin moves with 8-nm steps, similar to biological motors that move with regular steps.
Abstract: Do biological motors move with regular steps? To address this question, we constructed instrumentation with the spatial and temporal sensitivity to resolve movement on a molecular scale. We deposited silica beads carrying single molecules of the motor protein kinesin on microtubules using optical tweezers and analysed their motion under controlled loads by interferometry. We find that kinesin moves with 8-nm steps.
1,829 citations
TL;DR: Isometric forces generated by single molecules of the mechanochemical enzyme kinesin were measured with a laser-induced, single-beam optical gradient trap and the ability to measure force parameters of single macromolecules now allows direct testing of molecular models for contractility.
Abstract: Isometric forces generated by single molecules of the mechanochemical enzyme kinesin were measured with a laser-induced, single-beam optical gradient trap, also known as optical tweezers. For the microspheres used in this study, the optical tweezers was spring-like for a radius of 100 nanometers and had a maximum force region at a radius of approximately 150 nanometers. With the use of biotinylated microtubules and special streptavidin-coated latex microspheres as handles, microtubule translocation by single squid kinesin molecules was reversibly stalled. The stalled microtubules escaped optical trapping forces of 1.9 +/- 0.4 piconewtons. The ability to measure force parameters of single macromolecules now allows direct testing of molecular models for contractility.
425 citations
TL;DR: A fiber-optical version of a stable three-dimensional light-force trap is demonstrated, which has been used to hold and manipulate small dielectric spheres and living yeast.
Abstract: We demonstrate a fiber-optical version of a stable three-dimensional light-force trap, which we have used to hold and manipulate small dielectric spheres and living yeast. We show that the trap can be constructed by use of infrared diode lasers with fiber pigtails, without any external optics.
337 citations
TL;DR: A novel micromanipulator consisting of multiple optical traps created by scanning one single beam trap along a variable number of positions is developed which enables the orientation of irregularly shaped and relatively large structures which could not be oriented by just one trap as is demonstrated on long Escherichia coli bacteria filaments.
Abstract: We have developed a novel micromanipulator consisting of multiple optical traps created by scanning one single beam trap along a variable number of positions. Among other things, this enables the orientation of irregularly shaped and relatively large structures which could not be oriented by just one trap as is demonstrated on long Escherichia coli bacteria filaments. We expect that the multiple trap manipulator will broaden the field of applications of optical trapping as a micromanipulation technique. For example, it facilitates the study of mechanical properties of extended structures as illustrated by a "bending"-experiment using E. coli bacterium filaments. A special application of the multiple trap manipulator is the "indirect trapping" of objects which we did by keeping them held between other optically trapped particles. Indirect trapping makes it possible to trap particles which either cannot be trapped directly due to their optical properties (refractive index) or for which exposure to the laser radiation is undesirable. The multiple optical trap manipulator is controlled interactively by a UNIX workstation coupled to a VME instrumentation bus. This provides great flexibility in the control of the position and the orientation of the optical traps. Micromanipulation makes it desirable to have real time 3D microscopy for imaging and guidance of the optical traps. Therefore we integrated optical micromanipulation and a specially developed real-time confocal microscope. This so called bilateral confocal scanning laser microscope (bilateral CSLM) [Brakenhoff and Visscher, J Microsc 165:139-146, 1992] produces images at video rate.
184 citations
TL;DR: In this article, a Gaussian beam electromagnetic field model and a ray-optics model were used to predict axial trapping forces on polystyrene microspheres in water.
Abstract: Axial trapping forces exerted on microspheres are predicted using a Gaussian beam electromagnetic field model and a ray‐optics model, and compared with experimental measurements. Ray‐optics predicts a maximum trapping efficiency Q= −0.14 for optically trapped polystyrene microspheres in water, compared to a measured value of −0.12 ± 0.014 for 10 μm diam microspheres. When the microspheres are composed of amorphous silica, the predicted ray‐optics Q decreases to −0.11, compared to a Q = −0.034 predicted by the electromagnetic field model, and a measured value of −0.012 ± 0.001 for 1 μm diam microspheres. These results indicate that the two models have applicability in two different size regimes, and thus, are complementary.
164 citations
TL;DR: In this paper, a transient absorption microspectroscopic system with 200-fs temporal and micrometer (<25 μm) spatial resolutions was developed by using a microscope and a laser trapping technique using a pump beam, a white light continuum generated by focusing an intense femtosecond laser pulse into water, and a trapping laser beam were coaxially introduced into a microscope.
Abstract: A transient absorption microspectroscopic system with 200‐fs temporal and micrometer (<25 μm) spatial resolutions was developed by using a microscope and a laser trapping technique A pump beam, a white‐light continuum generated by focusing an intense femtosecond laser pulse into water, and a trapping laser beam were coaxially introduced into a microscope and focused onto a sample by a reflecting objective lens Advantages of a reflecting objective lens are discussed for the measurements of transient absorption spectra This method was applied to a dye‐doped single liquid droplet in water and α‐ and β‐perylene single microcrystals
23 citations
TL;DR: Use of a laser diode, collimated with a compact disc lens, provides a near-infrared light source that can be used for optical trapping and is compact and relatively cheap and can be easily incorporated into an existing microscope.
Abstract: We have designed and implemented an optical-trapping configuration that uses near-infrared laser diodes. The highly divergent output beam of the diode laser was collimated by using only one aspheric compact disc lens. The resulting output beams are astigmatic and elliptic and have a flat, non-Gaussian intensity profile. Calculations and measurements were performed to investigate the influence of this profile on the trapping forces. The results show that use of a laser diode, collimated with a compact disc lens, provides a near-infrared light source that can be used for optical trapping. The light source is compact and relatively cheap and can be easily incorporated into an existing microscope.
14 citations
Patent•
28 Sep 1993
TL;DR: An optical or laser trapping device (also known as an optical tweezer) is used to trap a particle within a fluid as mentioned in this paper, and the motion of the particle under the applied optical force is observed, for instance by detecting light reflected from the particle using an array of photodiodes.
Abstract: An optical or laser trapping device (also known as an optical tweezer) is used to trap a particle within a fluid. Usually the fluid is a liquid (2) and the particle (3) is suspended at the surface of the liquid. The particle is trapped in the optical tweezer and caused to move by an optical force created by displacing the beam (7), for instance by applying an electric field across a nicol prism (6) in the path of the beam. The motion of the particle under the applied optical force is observed, for instance by detecting light reflected from the particle using an array (10) of photodiodes. Preferably an oscillatory motion is applied to the beam and thence to the particle. The amplitude and/or frequency of the oscillation, as well as its phase relative to the phase of the laser beam motion, give information concerning the surface rheology, for instance the viscosity and elasticity, of the liquid. The apparatus is, for instance, used to observe clotting reactions in biological systems, for instance the clotting reaction of horseshoe crab amoebocyte upon contact with endotoxin.
13 citations
10 citations
TL;DR: A cell manipulator capable of trapping single living cells, making a direct binary contact from a chosen direction, and judging the formation of cell-to-cell adhesion is produced by means of optical trapping in combination with a fixed micropipette.
Abstract: A cell manipulator capable of (1) trapping single living cells, (2) making a direct binary contact from a chosen direction, and (3) judging the formation of cell-to-cell adhesion is produced by means of optical trapping in combination with a fixed micropipette. The specificity of the cell adhesive capability is tested with isolated hydra cells, demonstrating a clear difference in adhesive properties between ectodermal and endodermal epithelial cells
8 citations
15 Nov 1993
TL;DR: The recent results in modeling and measuring the optical trapping forces that are applied to dielectric microsphere and biological sperm cell samples are described.
Abstract: Optical tweezers are an important tool for use as non-contact micromanipulators of biological cells and organisms. The ability to apply optical forces in the pN regime means that optical tweezers can also be used as transducers of the fundamental forces responsible for cell locomotion, cell adhesion, and intracellular transport. Herein, we describe our recent results in modeling and measuring the optical trapping forces that are applied to dielectric microsphere and biological sperm cell samples. >
01 Jan 1993
TL;DR: In this paper, a scanned probe optical microscope allowing non-destructive studies of a wide range of objects and surfaces is described, which utilizes a non-intrusive optical trap to position a microscopic probe light source in immediate proximity to the studied object.
Abstract: A scanned probe optical microscope allowing non-destructive studies of a wide range of objects and surfaces is described. The microscope utilizes a non-intrusive optical trap to position a microscopic probe light source in immediate proximity to the studied object. Recent theoretical and experimental work aiming at optical imaging with sub-diffraction-limited resolution of, e.g., living biological objects, is discussed.
Abstract: The development of the single beam gradient force optical trap has improved the experimental capabilities available to cell biologists for noninvasive micromanipulation and mechanical measurement on living cells. Laser traps can be used not only to optically manipulate particles including bacteria, yeast cells, and intracellular organelles ranging in size from 25 nm to 25 micrometers with fine control of position (10 nm) but also to measure small (0.1 pN) forces in biological systems. For a given particle, trapping forces are linearly related to the laser power so that a relatively simple way of measuring force is to trap a particle at high power and gradually reduce it until the particle just escapes from the trap. The `escape' power, which is usually calibrated against the viscous drag of the aqueous medium at varying laser power levels, is a measure of the force.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
28 Oct 1993
TL;DR: In this paper, a two-beam opucal tweezer system is described that applies uniform trapping forces over a 100 x 100 pm2 scan field, with a deflection resolution of 10 nm.
Abstract: A scanning two-beam opucal tweezer system is described that applies uniform trapping forces over a 100 x 100 pm2 scan field, with a deflection resolution of 10 nm. The system, designed for the confinement, manipulation, and force measurement of non-spherical and elongated ceiIs and organisms, is applied to the study of chromosomes at two separate sites simultaneously. The application of optical trapping forces at multiple locations on a single cell or organism ptovides a new method far isolating and transporting single cells and organisms for subsequent diagnostic studies.
01 Jan 1993
TL;DR: Optical traps are intrinsically stable and localized in their effects as discussed by the authors and can be incorporated into relatively simple devices that allow single cells, chromosomes, and other cell organelles to be accurately positioned and transported.
Abstract: Optical trapping, a new technique for the manipulation of microscopic particles, was invented in the late ’60s by Arthur Ashkin of AT&T Bell Labs. This technique, examples of which were first reported by Ashkin (1970), relies on the pressure created by one or more laser beams that are scattered by a microscopic object in order to trap, levitate, and move that object. As opposed to other trapping techniques, optical traps are intrinsically stable and very localized in their effects. As such, they can be incorporated into relatively simple devices that allow single cells, chromosomes, and other cell organelles to be accurately positioned and transported. Furthermore, optical trapping only requires low-intensity laser beams and can be operated at wavelengths at which absorption by the trapped particle is minimized. As reported in Ashkin and Dziedzic (1987) and Ashkin et al. (1987), the trapping laser beams seem to have negligible biological effects on most cells that have been optically trapped.