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Optical tweezers/ Photochromic


313

Author(s): Otto, O (Otto, Oliver); Gutsche, C (Gutsche, Christof); Kremer, F (Kremer, Friedrich); Keyser, UF (Keyser, Ulrich F.)

Title: Optical tweezers with 2.5 kHz bandwidth video detection for single-colloid electrophoresis - art. no. 023710

Source: REVIEW OF SCIENTIFIC INSTRUMENTS, 79 (2): 23710-23710 Part 1 FEB 2008

Abstract:

We developed an optical tweezers setup to study. the electrophoretic motion of colloids in an external electric field. The setup is based on standard components for illumination and video detection. Our video based optical tracking of the colloid motion has a time resolution of 0.2 ms, resulting in a bandwidth of 2.5 kHz. This enables calibration of the optical tweezers by Brownian motion without applying a quadrant photodetector. We demonstrate that our system has a spatial resolution of 0.5 nm and a force sensitivity of 20 fN using a Fourier algorithm to detect periodic oscillations of the trapped colloid caused by an external ac field. The electrophoretic mobility and zeta potential of a single colloid can be extracted in aqueous solution avoiding screening effects common for usual bulk measurements. (C) 2008 American Institute of Physics.


Addresses: Univ Leipzig, Inst Expt Phys 1, D-04103 Leipzig, Germany

Univ Cambridge, Cavendish Lab, Cambridge CB3 0HE, England

Reprint Address: KEYSER, UF, UNIV LEIPZIG, INST EXPT PHYS 1, LINNESTR 5, D-04103 LEIPZIG, GERMANY

Author's E-mail: keyser@physik.um-Ieipzig.de

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314


Author(s): Li, C (Li, Chuan); Liu, KK (Liu, K. K.)

Title: Nanomechanical characterization of red blood cells using optical tweezers

Source: JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 19 (4): 1529-1535 APR 2008

Abstract:

Deformation behaviours of red blood cells (RBCs) have been studied by applying stretching forces via optical tweezers. Combined with finite-element analyses (FEA), the RBCs' mechanical properties are determined quantitatively based on a best fitting between the experimental deformed geometries and the simulated counterparts. Experimentally, a silica beads attached erythrocyte is optical-mechanically stretched to different lengths. On the theoretical front, a large deformation model with Mooney-Rivlin constitutive equations has been simulated by using FEA to predict the cell deformation geometries. The numerically simulated transverse and longitudinal strains which are in a good agreement with the experimental measurements facilitate the determination of elastic constants of the cells.
Addresses: Keele Univ, Inst Sci & Technol, Stoke On Trent ST4 7QB, Staffs, England

Nanyang Technol Univ, Sch Mech & Aerosp Engn, Singapore 639798, Singapore

Reprint Address: LIU, KK, KEELE UNIV, INST SCI & TECHNOL, THORNBURROW DR, STOKE ON TRENT ST4 7QB, STAFFS, ENGLAND

Author's E-mail: i.k.liu@keele.ac.uk

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315


Author(s): Li, Q (Li Qin); Feng, WL (Feng Wan-Li); Hu, XM (Hu Xiao-Ming); Cao, Q (Cao Qun); Sha, DG (Sha Ding-Guo); Lin, JM (Lin Jia-Ming)

Title: Theoretical study of the trapping efficiency of an optical tweezers array system

Source: CHINESE PHYSICS B, 17 (2): 726-735 FEB 2008

Abstract:

Optical tweezers have been a valuable research tool since their invention in the 1980s. One of the most important developments in optical tweezers in recent years is the creation of two-dimensional arrays of optical traps. In this paper, a method based on interference is discussed to form gradient laser fields, which may cause the spatial modulation of particle concentration. The parameters related to the optical tweezers array are discussed in detail and simulated by the Matlab software to show the influence of important parameters on the distribution of particle concentration. The spatial redistribution of particles in a laser interference field can also be predicted according to the theoretical analysis.
Addresses: Beijing Inst Technol, Dept Biomed Engn, Beijing 100081, Peoples R China

Beijing Inst Technol, Dept Optoelect Engn, Beijing 100081, Peoples R China

Reprint Address: LI, Q, BEIJING INST TECHNOL, DEPT BIOMED ENGN, BEIJING 100081, PEOPLES R CHINA

Author's E-mail: liqin70@bit.edu.cn

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316


Author(s): Takahashi, K (Takahashi, Kenji); Ichikawa, M (Ichikawa, Masatoshi); Kimura, Y (Kimura, Yasuyuki)

Title: Force between colloidal particles in a nematic liquid crystal studied by optical tweezers - art. no. 020703

Source: PHYSICAL REVIEW E, 77 (2): 703-703 Part 1 FEB 2008

Abstract:

We measure the dependence of the interparticle force F on the distance R between two colloidal particles with hyperbolic hedgehog defects in a nematic liquid crystal using optical tweezers. The particle-defect pair can be regarded as an elastic "dipole" in the electrostatic analogy. In a parallel configuration, where the dipole vectors are parallel with each other, F is attractive and proportional to R-4. However, F becomes repulsive at small R due to the existence of a defect between the particles. In an antiparallel configuration, where the particles directly face each other, F is repulsive over the whole range of R and proportional to R-3.6. In another antiparallel configuration, where two hyperbolic hedgehog defects directly face each other, F is proportional to R-3.6 and F at small R turns out to be attractive upon tilting the dipoles. Furthermore, we yield the force between particles connected by a stringlike defect called a bubblegum defect.
Addresses: Kyushu Univ, Sch Sci, Dept Phys, Higashi Ku, Fukuoka 8128581, Japan

Reprint Address: TAKAHASHI, K, KYUSHU UNIV, SCH SCI, DEPT PHYS, HIGASHI KU, 6-10-1 HAKOZAKI, FUKUOKA 8128581, JAPAN

Author's E-mail: ken8scp@mbox.nc.kyushu-u.ac.jp

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317

Author(s): Thomson, LC (Thomson, Laura C.); Boissel, Y (Boissel, Yannick); Whyte, G (Whyte, Graeme); Yao, E (Yao, Eric); Courtial, J (Courtial, Johannes)



Title: Simulation of superresolution holography for optical tweezers - art. no. 023015

Source: NEW JOURNAL OF PHYSICS, 10: 23015-23015 FEB 13 2008

Abstract:

Optical tweezers manipulate microscopic particles using foci of light beams. Their performance is therefore limited by diffraction. Using computer simulations of a model system, we investigate the application of superresolution holography for two-dimensional (2D) light shaping in optical tweezers, which can beat the diffraction limit. We use the direct-search and Gerchberg algorithms to shape the center of a light beam into one or two bright spots; we do not constrain the remainder of the beam. We demonstrate that superresolution algorithms can significantly improve the normalized stiffness of an optical trap and the minimum separation at which neighboring traps can be resolved. We also test if such algorithms can be used interactively, as is desirable in optical tweezers.


Addresses: Univ Glasgow, Dept Phys & Astron, SUPA, Glasgow G12 8QQ, Lanark, Scotland

Reprint Address: COURTIAL, J, UNIV GLASGOW, DEPT PHYS & ASTRON, SUPA, GLASGOW G12 8QQ, LANARK, SCOTLAND

Author's E-mail: j.courtial@physics.gla.ac.uk

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318

Author(s): Farias, PMA (Farias, Patricia M. A.); Santos, BS (Santos, Beate S.); de Thomaz, AA (de Thomaz, Andre A.); Ferreira, R (Ferreira, Ricardo); Menezes, FD (Menezes, Frederico D.); Cesar, CL (Cesar, Carlos L.); Fontes, A (Fontes, Adriana)



Title: Fluorescent II-VI semiconductor quantum dots in living cells: Nonlinear microspectroscopy in an optical tweezers system

Source: JOURNAL OF PHYSICAL CHEMISTRY B, 112 (9): 2734-2737 MAR 6 2008

Abstract:

In this work we used a setup consisting of an optical tweezers combined with a nonlinear microspectroscopy system to perform scanning microscopy and obtain emission spectra using two photon excited (TPE) luminescence of captured single living cells labeled with core-shell fluorescent semiconductor quantum dots (QDs). The QDs were obtained via colloidal synthesis in aqueous medium with an adequate physiological resulting pH. Sodium polyphosphate was used as the stabilizing agent. The results obtained show the potential presented by this system as well as by these II-VI fluorescent semiconductor quantum dots to perform spectroscopy in living trapped cells in any neighborhood and dynamically observe the cell chemical reactions in real time.


Addresses: Univ Fed Pernambuco, Dept Biofis & Radiobiol, Recife, PE, Brazil

Univ Fed Pernambuco, Dept Ciencias Farmaceut, Recife, PE, Brazil

Univ Estadual Campinas, Inst Fis Gleb Wataghin, Campinas, SP, Brazil

Univ Fed Pernambuco, Dept Quim Fundamental, Recife, PE, Brazil

Reprint Address: FARIAS, PMA, UNIV FED PERNAMBUCO, DEPT BIOFIS & RADIOBIOL, RECIFE, PE, BRAZIL

Author's E-mail: pmaf@ufpe.br

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319


Author(s): Minzioni, P (Minzioni, Paolo); Bragheri, F (Bragheri, Francesca); Liberale, C (Liberale, Carlo); Di Fabrizio, E (Di Fabrizio, Enzo); Cristiani, I (Cristiani, Ilaria)

Title: A novel approach to fiber-optic tweezers: Numerical analysis of the trapping efficiency

Source: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, 14 (1): 151-157 JAN-FEB 2008

Abstract:

We present a novel all-fiber optical tweezer (OT) for biological applications. The tweezer is based on a new approach relying on total internal reflection in an annular core fiber or into a fiber bundle. The proposed device, whose trapping efficacy has been recently demonstrated experimentally, is extremely promising, also because optical manipulation and analysis functions can be easily added to the tweezer basic structure, leading to the realization of a powerful biotool. In this paper, a detailed numerical analysis of the structure properties and of its efficiency is carried out in the Mie regime. Moreover, by defining a new parameter to evaluate the trapping efficiency, we perform a comparison between the proposed tweezer structure and a standard OT based on a strongly focused Gaussian beam.
Addresses: CNISM, I-27100 Pavia, Italy

Univ Pavia, I-27100 Pavia, Italy

Magna Graecia Univ Catanzaro, Dipartimento Med Sperimentale & Clin, I-88100 Catanzaro, Italy

Reprint Address: MINZIONI, P, CNISM, I-27100 PAVIA, ITALY

Author's E-mail: paolo.minzioni@unipv.it

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320

Author(s): Schonbrun, E (Schonbrun, Ethan); Rinzler, C (Rinzler, Charles); Crozier, KB (Crozier, Kenneth B.)



Title: Microfabricated water immersion zone plate optical tweezer - art. no. 071112

Source: APPLIED PHYSICS LETTERS, 92 (7): 71112-71112 FEB 18 2008

Abstract:

We demonstrate the trapping of beads in water with a microfabricated Fresnel zone plate. Beads are loaded onto the microfabricated optical traps using conventional optical tweezers and fluorescence microscopy is used to track bead position. Analysis of the bead position as a function of time is used to determine trapping stiffness. We present experiments showing the three-dimensional trapping of 2 mu m diameter beads with trapping stiffnesses that are comparable to conventional optical tweezers when the zone plate efficiency is taken into account. (C) 2008 American Institute of Physics.


Addresses: Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA

Reprint Address: SCHONBRUN, E, HARVARD UNIV, SCH ENGN & APPL SCI, CAMBRIDGE, MA 02138 USA

Author's E-mail: kcrozier@seas.harvard.edu

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321

Author(s): Andersson, M (Andersson, Magnus); Axner, O (Axner, Ove); Almqvist, F (Almqvist, Fredrik); Uhlin, BE (Uhlin, Bernt Eric); Fallman, E (Fallman, Erik)



Title: Physical properties of biopolyrners assessed by optical tweezers: Analysis of folding and refolding of bacterial pili

Source: CHEMPHYSCHEM, 9 (2): 221-235 FEB 1 2008

Abstract:

Bacterial adhesion to surfaces mediated by specific adhesion organelles that promote infections, as exemplified by the pill of uropathogenic E. coli, is studied mostly at the level of cell-cell interactions and thereby reflects the averaged behavior of multiple pill. The role of pilus rod structure has therefore only been estimated from the outcome of experiments involving large numbers of organelles at the some time. It has, however, lately become clear that the biomechanical behavior of the pilus shafts play an important, albeit hitherto rather unrecognized, role in the adhesion process. For example, it has been observed that shafts from two different strains, even though they are similar in structure, result in large differences in the ability of the bacteria to adhere to their host tissue. However, in order to identify all properties of pilus structures that ore of importance in the adhesion process, the biomechanical properties of pili must be assessed at the single-molecule level. Due to the low range of forces of these structures, until recently it was not possible to obtain such information. However, with the development of force-measuring optical tweezers (FMOT) with force resolution in the low piconewton range, it has lately become possible to assess forces mediated by individual pili on single living bacteria in real time. FMOT allows for a more or less detailed mapping of the biomechanical properties of individual pilus shafts, in particular those that are associated with their elongation and contraction under stress. This Minireview presents the FMOT technique, the biological model system, and results from assessment of the biomechanical properties of bacterial pili. The information retrieved is also compared with that obtained by atomic force microscopy.


Addresses: Umea Univ, Dept Phys, S-90187 Umea, Sweden

Umea Univ, Dept Organ Chem, S-90187 Umea, Sweden

Dept Mol Biol, S-90187 Umea, Sweden

Reprint Address: FALLMAN, E, UMEA UNIV, DEPT PHYS, S-90187 UMEA, SWEDEN

Author's E-mail: erik.fallman@physics.umu.se

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322

Author(s): Nieminen, TA (Nieminen, Timo A.); Heckenberg, NR (Heckenberg, Norman R.); Rubinsztein-Dunlop, H (Rubinsztein-Dunlop, Halina)



Title: Forces in optical tweezers with radially and azimuthally polarized trapping beams

Source: OPTICS LETTERS, 33 (2): 122-124 JAN 15 2008

Abstract:

It has been suggested that radially polarized beams can be used to improve the performance of optical tweezers, with reduced scattering force resulting from both the polarization and the dark center of the beam [Opt. Lett. 32, 1839 (2007)]. We calculate the forces on particles in such traps, using rigorous electromagnetic theory, comparing the results with azimuthally polarized beam, circularly polarized LG(01) beams, and Gaussian beams. Our results agree qualitatively with Opt. Lett. 32, 1839 (2007), but differ quantitatively. (c) 2008 Optical Society of America.


Addresses: Univ Queensland, Sch Phys Sci, Ctr Biophoton & Laser Sci, Brisbane, Qld 4072, Australia

Reprint Address: NIEMINEN, TA, UNIV QUEENSLAND, SCH PHYS SCI, CTR BIOPHOTON & LASER SCI, BRISBANE, QLD 4072, AUSTRALIA

Author's E-mail: timo@physics.uq.edu.au

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323

Author(s): Liao, GB (Liao, Guan-Bo); Bareil, PB (Bareil, Paul B.); Sheng, YL (Sheng, Yunlong); Chiou, A (Chiou, Arthur)



Title: One-dimensional jumping optical tweezers for optical stretching of bi-concave human red blood cells

Source: OPTICS EXPRESS, 16 (3): 1996-2004 FEB 4 2008

Abstract:

We report the experimental demonstration of optical stretching of individual bio-concave human red blood cells (RBCs) with one-dimensional jumping optical tweezers. We trapped a RBC in isotonic buffer solution in a conventional stationary single-beam gradient-force optical trap and discretely scanned the trapping beam with an acousto-optic modulator such that the focal point of the trapping beam jumped back-and-forth between two fixed points. At the jumping frequency on the order of a 100 Hz and higher, and the jumping distance in the range of a few microns, the biconcave RBC was stably trapped and stretched. The elongation of the stretched RBC was measured as a function of the beam-scanning amplitude, and the experimental results were explained qualitatively by a theoretical model. (C) 2007 Optical Society of America.


Addresses: Natl Yang Ming Univ, Inst Biophoton Engn, Taipei 112, Taiwan

Univ Laval, Ctr Opt Photon & Laser, Quebec City, PQ G1K 7P4, Canada

Reprint Address: LIAO, GB, NATL YANG MING UNIV, INST BIOPHOTON ENGN, TAIPEI 112, TAIWAN

Author's E-mail: sheng@phy.ulaval.ca

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324


Author(s): Maruyama, H (Maruyama, Hisataka); Arai, F (Arai, Fumihito); Fukuda, T (Fukuda, Toshio)

Title: On-chip pH measurement using functionalized gel-microbeads positioned by optical tweezers

Source: LAB ON A CHIP, 8 (2): 346-351 2008

Abstract:

This paper demonstrates local pH measurement in a microchip using a pH-sensing gel-microbead. To achieve this, the gel-microbead made of a hydrophilic photo-crosslinkable resin was functionalized with the pH indicator bromothymol blue (BTB). The primary constituent of this photo-crosslinkable resin is poly(ethylene glycol). Gel-microbeads impregnated with BTB were obtained by stirring the mixture solution, which was composed of the resin, BTB, and an electrolyte solution. The gel-microbead is polymerized by UV illumination. The polymerized gel-microbead can be manipulated by optical tweezers and made to adhere to a glass surface. The local pH was measured from the color of the gel-microbead impregnated with BTB by calibrated color information in the YCrCb color space. We succeeded in measuring the local pH value using the pH-sensing gel-microbead by manipulating and positioning it at the desired point in the microchip.
Addresses: Nagoya Univ, Dept Micronano Syst Engn, Chikusa Ku, Nagoya, Aichi 4648603, Japan

Tohoku Univ, Dept Bioengn & Robot, Aoba Ku, Sendai, Miyagi 9808579, Japan

Reprint Address: MARUYAMA, H, NAGOYA UNIV, DEPT MICRONANO SYST ENGN, CHIKUSA KU, NAGOYA, AICHI 4648603, JAPAN

Author's E-mail: maruyama@robo.mein.nagoya-u.ac.jp

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325


Author(s): Zhou, JH (Zhou Jin-Hua); Qu, LJ (Qu Lian-Jie); Yao, K (Yao Kun); Zhong, MC (Zhong Min-Cheng); Li, YM (Li Yin-Mei)

Title: Observing nanometre scale particles with light scattering for manipulation using optical tweezers

Source: CHINESE PHYSICS LETTERS, 25 (1): 329-331 JAN 2008

Abstract:

Nanometre-scale particles can be manipulated using optical tweezers, but cannot be directly observed. We present a simple method that nanoparticles can be directly observed using optical tweezers combined with dark field microscopy. A laser beam perpendicular to a tightly focused laser beam for trap illuminates specimen and does not enter objective, nanoparticles in focal plane all can be directly observed in dark field because of light scattering. It is implemented that the polystyrene beads of diameter 100nm can be directly observed and trapped.
Addresses: Univ Sci & Technol China, Dept Phys, Hefei 230026, Peoples R China

Reprint Address: LI, YM, UNIV SCI & TECHNOL CHINA, DEPT PHYS, HEFEI 230026, PEOPLES R CHINA

Author's E-mail: liyinmei@ustc.edu.cn

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326

Author(s): Campbell, KS (Campbell, Kenneth S.); Lakie, M (Lakie, Martin)



Title: Response to Bianco et al.: Interaction forces between F-actin and titin PEVK domain measured with optical tweezers

Source: BIOPHYSICAL JOURNAL, 94 (1): 327-328 JAN 1 2008

Abstract:

A recent publication in Biophysical Journal by Bianco et al.("Interaction forces between F-actin and titin PEVK domain measured with optical tweezers'') shows that the PEVK domain of titin molecules interacts with F-actin. This newly discovered behavior could influence the mechanical properties of striated muscles, and Bianco et al. suggest that the interactions between actin and titin could modulate thixotropic behavior. In this Comment to the Editor, we suggest that the thixotropic properties of striated muscles in vivo are more likely to reflect dynamic changes in the proportion of myosin cross-bridges bound between the myofilaments.


Addresses: Univ Kentucky, Dept Physiol, Lexington, KY 40536 USA

Univ Birmingham, Sch Sport & Exercise Sci, Appl Physiol Res Grp, Birmingham, W Midlands, England

Reprint Address: CAMPBELL, KS, UNIV KENTUCKY, DEPT PHYSIOL, MS-508 CHANDLER MED CTR,800 ROSE ST, LEXINGTON, KY 40536 USA

Author's E-mail: k.s.campbell@uky.edu

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327


Author(s): Li, M (Li, Martin); Arlt, J (Arlt, Jochen)

Title: Trapping multiple particles in single optical tweezers

Source: OPTICS COMMUNICATIONS, 281 (1): 135-140 JAN 1 2008

Abstract:

Optical trapping of multiple particles in three dimensions in a single inverted optical tweezers is investigated. The effect of trapping pairs of beads on the voltage signal recorded by a quadrant photo diode detector is examined, with particular emphasise on its power spectral density. It is found that trapped pairs of beads could be mistaken for single beads in a trap of half the strength. Stokes drag measurements reveal that both beads of the pair are confined less than a single particle in the same trap and that the quadrant signal provides some information of their mean displacements. (c) 2007 Elsevier B.V. All rights reserved.
Addresses: Univ Reading, Dept Phys, Reading RG6 6AF, Berks, England

Reprint Address: ARLT, J, UNIV EDINBURGH, SCH PHYS, SUPA, COSMIC, KINGS BLDG, EDINBURGH EH9 3JZ, MIDLOTHIAN, SCOTLAND

Author's E-mail: j.arlt@ed.ac.uk

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328

Author(s): Wood, TA (Wood, Tiffany A.); Roberts, GS (Roberts, G. Seth); Eaimkhong, S (Eaimkhong, Sarayoot); Bartlett, P (Bartlett, Paul)



Title: Characterization of microparticles with driven optical tweezersw

Source: FARADAY DISCUSSIONS, 137: 319-333 2008

Abstract:

We discuss how actively- driven optical tweezers may be used to characterize Brownian microparticles. Two experiments are described in detail. We follow the thermal fluctuations of a charged particle in an oscillatory electricfield and demonstrate that charges as low as a few elementary charges can be measured accurately and reproducibly. Secondly, we measure the orientational dynamics of a trapped rotating droplet and use circular polarimetry within optical tweezers to determine in situ birefringence.


Addresses: Univ Bristol, Sch Chem, Bristol BS8 1TS, Avon, England

Reprint Address: BARTLETT, P, UNIV BRISTOL, SCH CHEM, CANTOCKS CLOSE, BRISTOL BS8 1TS, AVON, ENGLAND

Author's E-mail: p.bartlett@bristol.ac.uk

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