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Proceedings Paper

Single-cell and single-molecule laser biotechnology
Author(s): Karl-Otto Greulich; Eckhard Bauer; Ursula Fiedler; Carsten Hoyer; Karsten Koenig; Shamci Monajembashi
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Paper Abstract

While lasers have found a wide field of application in the analysis of cells and biomolecules, their use in manipulation is less common. Now, new applications of lasers are emerging, which aim at cells and even molecules as biotechnological individuals: For example, in single cell gel electrophoresis individual cells are irradiated by UV laser pulses which cause radiation damage to DNA. When the whole cell is positioned in an electric field and the UV induced damages are converted into DNA strand breaks, the resulting DNA fragments are eluted out of the cell nucleus. Small fragments are running further than large ones. After staining of the DNA fragments, the cell has the appearance like a comet (therefore comet assay). The tail moment, a parameter quantifying the shape of the tail, gives information on the degree of DNA damage. The kinetics of DNA damage induction can be described by a type of exponential law with parameters which are related to radiation sensitivity of the DNA. A further emerging technique aims at DNA as a molecular individuum. One pivotal step for single molecule DNA analysis is single molecule handling. For that purpose, a DNA molecule is coupled to a micrometer sized polystyrene bead, either via an avidin-biotin bridge or, more specifically, by strand recognition, and labeled with fluorescence dyes such as DAPI. In order to visualize the dynamics of individual DNA molecules, highly sensitive video processing and single photon counting is required. Moving the polystyrene bead using optical tweezers, the molecule can be deformed, i.e., bent, turned or stretched. Using a laser microbeam, the same individual molecule can be cut into smaller portions.

Paper Details

Date Published: 8 January 1996
PDF: 8 pages
Proc. SPIE 2629, Biomedical Optoelectronics in Clinical Chemistry and Biotechnology, (8 January 1996); doi: 10.1117/12.229503
Show Author Affiliations
Karl-Otto Greulich, Institut fuer Molekulare Biotechnologie (Germany)
Eckhard Bauer, Institut fuer Molekulare Biotechnologie (Germany)
Ursula Fiedler, Institut fuer Molekulare Biotechnologie (Germany)
Carsten Hoyer, Institut fuer Molekulare Biotechnologie (Germany)
Karsten Koenig, Institut fuer Molekulare Biotechnologie (Germany)
Shamci Monajembashi, Institut fuer Molekulare Biotechnologie (Germany)


Published in SPIE Proceedings Vol. 2629:
Biomedical Optoelectronics in Clinical Chemistry and Biotechnology
Stefan Andersson-Engels; Mario Corti; Ivan Kertesz; Norbert Kroo; Heinz P. Weber; Terence A. King; Riccardo Pratesi; Stefan Seeger, Editor(s)

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