Optical Torque Wrench: Angular Trapping, Rotation, and Torque Detection of Quartz Microparticles

Porta, A. La; Wang, Michelle D.

doi:10.1103/physrevlett.92.190801

Cited by 350 publications

(284 citation statements)

References 19 publications

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“…Because the change in plectoneme number constitutes the signal used for the detection of initiation, torque and tension are interdependent and cannot be varied at will in magnetic tweezer assays. Newer forms of sensitive optical instrumentation are being developed that may permit a wider range of torques and tensions to be explored at high bandwidth (52).…”

Section: Open-complex Formationmentioning

confidence: 99%

Single-Molecule Studies of RNA Polymerase: Motoring Along

Herbert

Greenleaf

Block

2008

Annu. Rev. Biochem.

189

141

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Single-molecule techniques have advanced our understanding of transcription by RNA polymerase. A new arsenal of approaches, including single-molecule fluorescence, atomic-force microscopy, magnetic tweezers, and optical traps have been employed to probe the many facets of the transcription cycle. These approaches supply fresh insights into the means by which RNA polymerase identifies a promoter; initiates transcription, translocates and pauses along the DNA template, proofreads errors, and ultimately terminates transcription. Results from single-molecule experiments complement knowledge gained from biochemical and genetic assays by facilitating the observation of states that are otherwise obscured by ensemble averaging, such as those resulting from heterogeneity in molecular structure, elongation rate, or pause propensity. Most studies to date have been performed with bacterial RNA polymerase, but work is also being carried out with eukaryotic polymerase (Pol II) and single-subunit polymerases from bacteriophages. We discuss recent progress achieved by single-molecule studies, highlighting some of the unresolved questions and ongoing debates.

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Section: Open-complex Formationmentioning

confidence: 99%

Single-Molecule Studies of RNA Polymerase: Motoring Along

Herbert

Greenleaf

Block

2008

Annu. Rev. Biochem.

189

141

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“…The optical radiation torque [1] which arises from the transfer of angular momentum of light to a (lossy) dielectric sphere has received significant attention in optical levitation [2-4] and particle rotation applications in atomic physics [5,6], cell biology [7] and other areas [8,9]. In common optical laser beams, and under some conditions related to the particle absorptive properties, a spin torque causing the particle to rotate around its center of mass arises, in addition to an orbital component causing the particle to rotate around the beam's axis of wave propagation [1].…”

Section: Abstract: Negative Spin Torque Dielectric Sphere Dipole Apmentioning

confidence: 99%

Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

Mitri

2016

Journal of Quantitative Spectroscopy and Radiative Transfer

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-An absorptive Rayleigh dielectric sphere in a non-diffracting non-paraxial fractional Bessel vortex beam experiences a spin torque. The axial and transverse radiation spin torque components are evaluated in the dipole approximation using the radiative correction of the electric field. Particular emphasis is given on the polarization as well as changing the topological charge  and the beam's half-cone angle. When  is zero, the axial spin torque component vanishes. However, when  becomes a real positive number, the vortex beam induces left-handed (negative) axial spin torque as the sphere shifts off-axially from the center of the beam. The results show that a non-diffracting non-paraxial fractional Bessel vortex beam is capable to induce a spin reversal of an absorptive Rayleigh sphere placed arbitrarily in its path. Potential applications are yet to be explored in particle manipulation, rotation in optical tweezers, optical tractor beams, the design of optically-engineered metamaterials to name a few areas. Keywords: Negative spin torque, dielectric sphere, dipole approximation.The optical radiation torque [1] which arises from the transfer of angular momentum of light to a (lossy) dielectric sphere has received significant attention in optical levitation [2-4] and particle rotation applications in atomic physics [5,6], cell biology [7] and other areas [8,9]. In common optical laser beams, and under some conditions related to the particle absorptive properties, a spin torque causing the particle to rotate around its center of mass arises, in addition to an orbital component causing the particle to rotate around the beam's axis of wave propagation [1]. Note that the orbital torque component exerted on the sphere vanishes at the center of the beam. Moreover, the sphere should be absorptive in order to experience a spin torque [1]. Various standard types of laser beams have been suggested and investigated for this purpose [10,11]. Examples of beams also include optical vortices of Gaussian-like [12,13] and nondiffracting beams [14].A particular kind of vortices with fractional topological charge (or order) has received increasing attention due to their special In contrast, another class for factional vortex beams (which can be realized experimentally using blazed-phase hologram encoded in a programmable liquid crystal display illuminated with a He-Ne laser [19]) and displays limited-diffracting features during propagation exists [19,20]. The physically-realizable apodized beam carrying finite energy preserves the nondiffracting propagation property. It is also known as a high-order Bessel vortex beam of fractional type  (HOBVB-F) [21][22][23]. A HOBVB-F with fractional order  connects standard nondiffracting Bessel (vortex) beams (Fig. 1) of successive integer order in a smooth transition. It also generates individual vortices in the (lateral) plane perpendicular to the axis of wave propagation corresponding to a cross-section of the incident nondiffracting beam [19]. This specific feature provides ...

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“…[22][23][24][25][26][27][28][29][30] Force-spectroscopy techniques such as magnetic tweezers and optical torque wrenches have been developed for mechanical measurements on supercoiled DNA with precise control of the tension and torque applied. [31][32][33] However, most of these single-molecule techniques merely measure the end-to-end extension of the DNA which provides only limited structural information. Real-time visualization of the dynamics of plectonemes within a single DNA molecule has only recently been achieved by combining fluorescence microscopy and magnetic tweezers in a side-pulling geometry.…”

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confidence: 99%

Intercalation-Based Single-Molecule Fluorescence Assay To Study DNA Supercoil Dynamics

et al. 2016

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DNA supercoiling crucially affects cellular processes such as DNA replication, gene expression, and chromatin organization. However, mechanistic understanding of DNA supercoiling and the related DNA-processing enzymes has remained limited, mainly due to the lack of convenient experimental tools to probe these phenomena. Here, we report a novel high-throughput single-molecule assay for real-time visualization of supercoiled DNA molecules, named ISD (Intercalation-induced Supercoiling of DNA). We use an intercalating dye to induce supercoiling of surface-attached DNA molecules as well as to visualize coiled-loop structures (i.e., plectonemes) formed on DNA. The technique is solely based on epifluorescence microscopy and requires no mechanical manipulation of the DNA molecules. This new assay allows to track positions and sizes of individual plectonemes and characterize their position-dependent dynamics such as nucleation, termination, and diffusion. We describe the ISD technique and demonstrate its potential by establishing that plectonemes are pinned to a local 10-nucleotide long mispaired sequence along a double-stranded DNA molecule.

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Optical Torque Wrench: Angular Trapping, Rotation, and Torque Detection of Quartz Microparticles

Cited by 350 publications

References 19 publications

Single-Molecule Studies of RNA Polymerase: Motoring Along

Single-Molecule Studies of RNA Polymerase: Motoring Along

Negative optical spin torque wrench of a non-diffracting non-paraxial fractional Bessel vortex beam

Intercalation-Based Single-Molecule Fluorescence Assay To Study DNA Supercoil Dynamics

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