Tweezers, optical

Optical tweezers are based on the premise that a particle placed into the focus of a collimated laser beam will feel two optical forces. The first one is the scattering force. 

To apply a force with optical tweezers to single molecules, typically a spherical particle of 1 pm diameter is trapped with the laset The bead will ad as a handle to 

Around 1970 it was found that laser radiation forces can be used to trap and manipulate small dielectric particles [83]. A laser beam can push a particle towards the centre of the beam, provided the particle has a higher refractive index than the surrounding medium. Thus, optical tweezers allow to pick up and manipulate 

A major advantage of optical tweezers is that the detected forces range between 10 and 10 N. Like TIRM, optical tweezers enable studying colloidal interactions in a non-invasive manner. Complementary to TIRM it enables to measure the interaction potentials between two colloidal particles, whereas TIRM and AFM 

The pair interaction measured using optical tweezers between two silica spheres in the presence of rather monodisperse, non-adsorbing DNA chains [89] is plotted in Fig. 2.39. Data are given for three DNA concentrations beyond the coil overlap concentration indicated in the plot. 

Division of Physical Biochemistry, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 lAA, UK 

The major impact of optical tweezers in biology arises from their use in the rapidly expanding field of single-molecule research. By chance, the optical forces produced by commonly available lasers (with output powers of a few hundred milliwatts) happen to be in the piconewton (pN) range, which is just right to experiment with 

Chemical Biology Edited by Banafshe Larijani, Colin. A. Rosser and Rudiger Woscholski 2006 John Wiley Sons, Ltd 

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Particles can be manipulated in suspension using strongly focused laser beams ( optical tweezers ) [25] or magnetic fields [26] and by collecting statistics on tire particle movements using video microscopy, infonnation on the particle interactions can be obtained. 

Nishizaka T, Miyata H, Yoshikawa H, Ishiwata S and Kinosita K 1995 Unbinding force of a single motor molecule of muscle measured using optical tweezers Nature 377 251-4... 

Experimental techniques based on the application of mechanical forces to single molecules in small assemblies have been applied to study the binding properties of biomolecules and their response to external mechanical manipulations. Among such techniques are atomic force microscopy (AFM), optical tweezers, biomembrane force probe, and surface force apparatus experiments (Binning et al., 1986 Block and Svoboda, 1994 Evans et ah, 1995 Israelachvili, 1992). These techniques have inspired us and others (see also the chapters by Eichinger et al. and by Hermans et al. in this volume) to adopt a similar approach for the study of biomolecules by means of computer simulations. 

Optical storage disks Optical storage media Optical switches Optical trapping Optical tweezers Optical wave guides... 

Although experimental studies of DNA and RNA structure have revealed the significant structural diversity of oligonucleotides, there are limitations to these approaches. X-ray crystallographic structures are limited to relatively small DNA duplexes, and the crystal lattice can impact the three-dimensional conformation [4]. NMR-based structural studies allow for the determination of structures in solution however, the limited amount of nuclear overhauser effect (NOE) data between nonadjacent stacked basepairs makes the determination of the overall structure of DNA difficult [5]. In addition, nanotechnology-based experiments, such as the use of optical tweezers and atomic force microscopy [6], have revealed that the forces required to distort DNA are relatively small, consistent with the structural heterogeneity observed in both DNA and RNA. 

Kuo, S. C. and Sheetz, M. P. (1993) force of single kinesin molecules measured with optical tweezers. Science, 260, 232-234. 

We have applied FCS to the measurement of local temperature in a small area in solution under laser trapping conditions. The translational diffusion coefficient of a solute molecule is dependent on the temperature of the solution. The diffusion coefficient determined by FCS can provide the temperature in the small area. This method needs no contact of the solution and the extremely dilute concentration of dye does not disturb the sample. In addition, the FCS optical set-up allows spatial resolution less than 400 nm in a plane orthogonal to the optical axis. In the following, we will present the experimental set-up, principle of the measurement, and one of the applications of this method to the quantitative evaluation of temperature elevation accompanying optical tweezers. 

Figure 8.6 Schematic illustration of the PCS system with optical tweezers.

With the aim of elucidating molecular dynamics in a small domain, we have constmcted several microspectroscopic systems, that is, (i) the confocal microscope with the excitation light source being a femtosecond NIR laser emitting a 35 fs pulse, and (ii) the fluorescence correlation spectroscopic system with optical tweezers. 

Agate, B., Brown, C., Sibbett, W. and Dholakia, K. (2004) Femtosecond optical tweezers for in-situ control of two-photon fluorescence. Opt. Express, 12, 3011-3017. 

In SMD an external force is applied in an attempt to accelerate a chemical process such as unfolding of a protein or dissociation of two molecules. In that respect, it is similar to AFM or optical-tweezers experiments. The applied force is given by ... 

Fuller, D.N., Gemmen, G.J., Rickgauer, J.P., Dupont, A., Millin, R., Recouvreux, P., and Smith, D.E. (2006) A general method for manipulating DNA sequences from any organism with optical tweezers. Nucleic Acids Res. 34, el5. 

In optical tweezer experiments, the optical scattering force is used to trap particles, but the force can also be used to control the shape of liquid droplets26. An infrared laser with 43-mW power focused onto a microdroplet on a superhydrophobic surface enabled up to 40% reversible tuning of the equatorial diameter of the droplet26. Such effects must naturally also be taken into account when exciting laser modes in droplets in experiments with levitated drops. 

Li Z, Anvari B, Takashima M, Brecht P, Torres JH, Brownell WE (2002) Membrane tether formation from outer hair cells with optical tweezers. Biophys. J. 82 1386-1395. 

Sleep, Wilson, D., Simmons, R., and Gratzer, W., Elasticity of the red cell membrane and its relation to hemolytic disorders an optical tweezers study, Biophys. /., 63, 1999, 3085-3095. 

Seeger, S., Monajembashi, S., Hutter, K.-J., Futterman, G., Wolfrum, J and Greulich, K. O. (1991) Application of laser optical tweezers in immunology and molecular genetics. Cytometry 12,497-504. 

Wiegand Steubing, R., Cheng, S., Wright, W. H., Numajiri, Y., and Bems, M. W. (1991) Laser induced cell fusion in combination with optical tweezers the laser cell fusion trap. Cytometry 12, 505-510. 

Chromatin fiber disassembly under applied force has been successfully studied so far only with optical tweezers. 

As mentioned earlier, the AFM data [70] set a lower limit of350 pN for the de-spooling process, while the OT data obtained in three different laboratories using three very different biological samples consistently gave a dissociation value of 20 pN. Why are the forces measured in the AFM and in the optical tweezers so... 

Bennink, M.L., Leuba, S.H., Leno, G.H., Zlatanova, J., de Grooth, B.G., and Greve, J. (2001) Unfolding individual nucleosomes by stretching single chromatin fibers with optical tweezers. Nat. Struct. Biol. 8, 606-610. 

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