Journal: bioRxiv
Article Title: Digital holography-based 3D particle localisation for single molecule tweezer techniques
doi: 10.1101/2022.05.03.490423
Figure Lengend Snippet: Comparison of HoloMiP and look-up table cross-correlation (LUT x-corr) for localising superparamagnetic microbeads. (a) An in silico synthetic diffraction pattern, positioned 10 μm from the focus, is moved in-plane by discrete steps (Δx). The x, y localisation through time of the diffraction pattern moving in steps of 19.5 nm (b) and 2 nm (c) are shown for each technique. The mean standard deviation was 0.68 nm for HoloMiP and 1.63 nm for the LUT. (d) The signal-to-noise ratios (SNR) are shown for each technique. The dashed line shows a SNR value of 1. (e) The through-plane resolution of the two techniques is tested by using a nano-positioning stage to move an immobilised microbead in steps (Δz) along the optical axis (z) after an initial defocusing of the microscope objective (Δf 0 ). Resolution of 30 nm steps with a 10 μm (f) and 20 μm defocus (g). (h) The corresponding SNR shows the two techniques are similar at a 10 μm defocus; however, HoloMiP outperforms the look-up table technique at the 20 μm defocus. (i) The magnetic field gradient ( ∇B ) from two permanent magnets induces a magnetic dipole ( μ ) in, and exerts an upwards force ( F mag ) on, a 2.8 μm magnetic microbead tethered to a 16.3 μm length of DNA. When the magnets are moved out of position, the microbead descends to the surface under gravity ( F grav ). (j, k, l) The position of the microbead in response to the magnetic field is tracked through time in 3D using both HoloMiP and the look-up table technique; blue shading indicates when a magnetic force of 15 pN is applied.
Article Snippet: Antibodies specific for CR2 (clone b-ly4, BD Biosciences) or for digoxigenin (sheep anti-digoxigenin, Bio-Rad Laboratories) were conjugated to 2.8 μm diameter superparamagnetic Dynabeads (M270 Epoxy; Thermo Fisher Scientific Inc.) using the manufacturer’s protocol.
Techniques: In Silico, Standard Deviation, Microscopy