Laser tweezers

Kellermayer et aJ., 1997] Kellermayer, M., Smith, S., Granzier, H., and Bustamante, C. Folding-unfolding transition in single titin modules characterized with laser tweezers. Science. 276 (1997) 1112-1116... 

In this chapter, we will show how nonequilibrium methods can be used to calculate equilibrium free energies. This may appear contradictory at first glance. However, as was shown by Jarzynski [1, 2], nonequilibrium perturbations can be used to obtain equilibrium free energies in a formally exact way. Moreover, Jarzynski s identity also provides the basis for a quantitative analysis of experiments involving the mechanical manipulation of single molecules using, e.g., force microscopes or laser tweezers [3-6]. 

Kellermayer MSZ, Smith SB, Granzier HL, Bustamante C. Folding-unfolding transitions in single titin molecules characterized with laser tweezers. Science 1997 276 1112-1126. 

Transcription of DNA and transportation by laser tweezer vesicles behaved as a barrier preventing the attack of RNAase. 

Tsumoto, K., Nomura, S. M., Nakatani, Y., and Yoshikawa, K. (2002). Giant liposome as a biochemical reactor transcription of DNA and transportation by laser tweezers. Langmuir, 17,7225-8. 

In terms of beam delivery, the DLW method is based on optical microscopy, confocal microscopy [4,6,13] and laser tweezers [14] (for reviews on laser tweezers see [ 15,16]). These techniques allow for a high spatial 3D resolution of a tightly focused laser beam with optical exposure of micrometric-sized volumes via linear and nonlinear absorption. In addition, mechanical and thermal forces can be exerted upon objects as small as 10 nm molecular dipolar alignment can be controlled by polarization of light in volumes of with submicrometric cross-sections. This circumstance widens the field of applications for laser nano- and microfabrication in liquid and solid materials [17-22]. 

A clever way to minimize the unwanted background from the cover plate or the environment is combining laser tweezers and confocal Raman spectroscopy (LTRS) [73, 74], While the single cells are levitated well off the surface and held in the focus of the laser beam the Raman spectral patterns of these cells are recorded with high sensitivity. Another appealing fact is the usage of one laser for both Raman excitation and optical trapping to keep the instrumental efforts as low as possible. Additionally the trapped cells can also be micro-manipulated and moved from one place to another, e.g., from the native matrix to a clean collection chamber. 

Recent laser-tweezer experiments used antibody pairs to demarcate tandem Ig segments within single titin molecules (Leake et al, 2004)... 

Optical trapping (also known as laser tweezers) 2.5 Diametrical compression (also called compression 35... 

Optical trapping (also known as laser tweezers)... 

Figure 12 Combination of dielectrophoretic field cage (DFC) and optical tweezers (OT) for the measurement of bead-cell adhesion (A) 4.1-(xm polystyrene particle trapped with laser tweezers (right) in contact with T-lymphoma cell ( — 1 5 pm in diameter). Cell and bead were brought into contact. The time for stable adhesion was measured. (B) Schematic representation of the experimental system used to measure the adhesion forces between bead and cell with the cell trapped in a DFC and the bead trapped in the laser focus of the OT. (C) Probing different surface regions of the cell for bead-cell adhesion (five beads are attached to a single cell). (Reprinted from Ref. 91 with permission.)...

There are other major objections to Crocker and Grier s claim [13, 14], one of which we consider in Chapter 7. First, there is the timescale of the measurements. The laser tweezer experiments measure transient collisions, whereas equilibrium in these dispersions usually takes weeks or months to achieve [17], Inspection of Figure 3.8 reveals that any transient experiment is going to be dominated by the medium-range strong repulsion. The minimum is so shallow that the true equilibrium nature of the forces takes weeks to reveal itself against the background of the Brownian motion. We also observed that when an n-butylammonium vermiculite gel had been compressed... 

The integration of laser tweezers with Raman spectroscopy for optical manipulation and spectroscopic analysis of individual micro- and nanoscopic objects in physics, chemistry, and the life sciences. 

In 1986, Ashkin and coworkers reported on the first successful single-beam gradient-force trap, or laser tweezers, for dielectric particles [21]. They were able to trap particles of glass, silica, and polystyrene (PS) in the range from 25 nm to 10 pm in water. Optical trapping techniques have since been integrated to a range of different... 

Zheng F, Qin YJ, Chen K (2007) Sensitivity map of laser tweezers Raman spectroscopy for single-cell analysis of colorectal cancer. J Biomed Opt 12(3) 034002 Chan JW et al (2008) Nondestmctive identification of iudividual leukemia cells by laser trapping Raman spectroscopy. Anal Chem 80(6) 2180-2187... 

Chan JW, Taylor DS, Thompson DL (2009) The effect of cell fixation on the discrimination of normal and leukemia cells with laser tweezers Raman spectroscopy. Biopolymers 91(2) 132-139... 

Rong X et al (2010) Real-time detection of single-living pancreatic beta-cell by laser tweezers Raman spectroscopy high glucose stimulation. Biopolymers 93(7) 587-594... 

Chan JW et al (2004) Reagentless identification of single bacterial spores in aqueaous solution by confocal laser tweezers Raman spectroscopy. Anal Chem 76 599-603... 

Konig K et al (1996) Effects of ultraviolet exposure and near infrared laser tweezers on human spermatozoa. Hum Reprod 11(10) 2162-2164... 

Xie, C., Mace, J., Dinno, M.A., Li, Y.Q., Tang, W., Newton, R.J. and Gemperline, P.J. (2005) Identification of single bacterial cells in aqueous solution using conflocal laser tweezers Raman spectroscopy. Anal.Chem., 77, 4390-4397. 

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