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  1. Article: All-optical constant-force laser tweezers.

    Nambiar, Rajalakshmi / Gajraj, Arivalagan / Meiners, Jens-Christian

    Biophysical journal

    2004  Volume 87, Issue 3, Page(s) 1972–1980

    Abstract: Optical tweezers are a powerful tool for the study of single biomolecules. Many applications require that a molecule be held under constant tension while its extension is measured. We present two schemes based on scanning-line optical tweezers to ... ...

    Abstract Optical tweezers are a powerful tool for the study of single biomolecules. Many applications require that a molecule be held under constant tension while its extension is measured. We present two schemes based on scanning-line optical tweezers to accomplish this, providing all-optical alternatives to force-clamp traps that rely on electronic feedback to maintain constant-force conditions for the molecule. In these schemes, a laser beam is rapidly scanned along a line in the focal plane of the microscope objective, effectively creating an extended one-dimensional optical potential over distances of up to 8 microm. A position-independent lateral force acting on a trapped particle is created by either modulating the laser beam intensity during the scan or by using an asymmetric beam profile in the back focal plane of the microscope objective. With these techniques, forces of up to 2.69 pN have been applied over distances of up to 3.4 microm with residual spring constants of <26.6 fN/microm. We used these techniques in conjunction with a fast position measurement scheme to study the relaxation of lambda-DNA molecules against a constant external force with submillisecond time resolution. We compare the results to predictions from the wormlike chain model.
    MeSH term(s) Biophysical Phenomena ; Biophysics ; DNA/chemistry ; DNA/ultrastructure ; Lasers ; Light ; Micromanipulation/instrumentation ; Micromanipulation/methods ; Microscopy/methods ; Microspheres ; Models, Statistical ; Scattering, Radiation ; Stress, Mechanical ; Time Factors
    Chemical Substances DNA (9007-49-2)
    Language English
    Publishing date 2004-09
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Research Support, U.S. Gov't, P.H.S.
    ZDB-ID 218078-9
    ISSN 1542-0086 ; 0006-3495
    ISSN (online) 1542-0086
    ISSN 0006-3495
    DOI 10.1529/biophysj.103.037697
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.A 235: Show issues Location:
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  2. Article: Three-dimensional characterization of tethered microspheres by total internal reflection fluorescence microscopy.

    Blumberg, Seth / Gajraj, Arivalagan / Pennington, Matthew W / Meiners, Jens-Christian

    Biophysical journal

    2005  Volume 89, Issue 2, Page(s) 1272–1281

    Abstract: Tethered particle microscopy is a powerful tool to study the dynamics of DNA molecules and DNA-protein complexes in single-molecule experiments. We demonstrate that stroboscopic total internal reflection microscopy can be used to characterize the three- ... ...

    Abstract Tethered particle microscopy is a powerful tool to study the dynamics of DNA molecules and DNA-protein complexes in single-molecule experiments. We demonstrate that stroboscopic total internal reflection microscopy can be used to characterize the three-dimensional spatiotemporal motion of DNA-tethered particles. By calculating characteristic measures such as symmetry and time constants of the motion, well-formed tethers can be distinguished from defective ones for which the motion is dominated by aberrant surface effects. This improves the reliability of measurements on tether dynamics. For instance, in observations of protein-mediated DNA looping, loop formation is distinguished from adsorption and other nonspecific events.
    MeSH term(s) DNA/analysis ; DNA/chemistry ; DNA/ultrastructure ; Image Enhancement/instrumentation ; Image Enhancement/methods ; Image Interpretation, Computer-Assisted/instrumentation ; Image Interpretation, Computer-Assisted/methods ; Imaging, Three-Dimensional/instrumentation ; Imaging, Three-Dimensional/methods ; Microscopy, Fluorescence/instrumentation ; Microscopy, Fluorescence/methods ; Microspheres ; Motion ; Nucleic Acid Conformation ; Stroboscopy/instrumentation ; Stroboscopy/methods
    Chemical Substances DNA (9007-49-2)
    Language English
    Publishing date 2005-08
    Publishing country United States
    Document type Evaluation Studies ; Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, Non-P.H.S. ; Research Support, U.S. Gov't, P.H.S.
    ZDB-ID 218078-9
    ISSN 1542-0086 ; 0006-3495
    ISSN (online) 1542-0086
    ISSN 0006-3495
    DOI 10.1529/biophysj.105.061242
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Cologne/Königswinter

    Zs.A 235: Show issues Location:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
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  3. Article: Mg2+-induced compaction of single RNA molecules monitored by tethered particle microscopy.

    Newby Lambert, Meredith / Vöcker, Eva / Blumberg, Seth / Redemann, Stefanie / Gajraj, Arivalagan / Meiners, Jens-Christian / Walter, Nils G

    Biophysical journal

    2006  Volume 90, Issue 10, Page(s) 3672–3685

    Abstract: We have applied tethered particle microscopy (TPM) as a single molecule analysis tool to studies of the conformational dynamics of poly-uridine(U) messenger (m)RNA and 16S ribosomal (r)RNA molecules. Using stroboscopic total internal reflection ... ...

    Abstract We have applied tethered particle microscopy (TPM) as a single molecule analysis tool to studies of the conformational dynamics of poly-uridine(U) messenger (m)RNA and 16S ribosomal (r)RNA molecules. Using stroboscopic total internal reflection illumination and rigorous selection criteria to distinguish from nonspecific tethering, we have tracked the nanometer-scale Brownian motion of RNA-tethered fluorescent microspheres in all three dimensions at pH 7.5, 22 degrees C, in 10 mM or 100 mM NaCl in the absence or presence of 10 mM MgCl(2). The addition of Mg(2+) to low-ionic strength buffer results in significant compaction and stiffening of poly(U) mRNA, but not of 16S rRNA. Furthermore, the motion of poly(U)-tethered microspheres is more heterogeneous than that of 16S rRNA-tethered microspheres. Analysis of in-plane bead motion suggests that poly(U) RNA, but less so 16S rRNA, can be modeled both in the presence and absence of Mg(2+) by a statistical Gaussian polymer model. We attribute these differences to the Mg(2+)-induced compaction of the relatively weakly structured and structurally disperse poly(U) mRNA, in contrast to Mg(2+)-induced reinforcement of existing secondary and tertiary structure contacts in the highly structured 16S rRNA. Both effects are nonspecific, however, as they are dampened in the presence of higher concentrations of monovalent cations.
    MeSH term(s) Adsorption ; Binding Sites ; Elasticity ; Magnesium/chemistry ; Microscopy, Atomic Force ; Nucleic Acid Conformation ; Particle Size ; RNA/chemistry ; RNA/ultrastructure ; Stress, Mechanical
    Chemical Substances RNA (63231-63-0) ; Magnesium (I38ZP9992A)
    Language English
    Publishing date 2006-05-15
    Publishing country United States
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S.
    ZDB-ID 218078-9
    ISSN 1542-0086 ; 0006-3495
    ISSN (online) 1542-0086
    ISSN 0006-3495
    DOI 10.1529/biophysj.105.067793
    Database MEDical Literature Analysis and Retrieval System OnLINE

    Full text online

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    In stock of ZB MED Cologne/Königswinter

    Zs.A 235: Show issues Location:
    Je nach Verfügbarkeit (siehe Angabe bei Bestand)
    bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
    Jg. 1995 - 2021: Lesesall (1.OG)
    ab Jg. 2022: Lesesaal (EG)
    Zs.MO 2: Show issues

    Order via subito

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