Biology subjects

Hulleman, C. N.

Publications and source records attributed to Hulleman, C. N..

3 recordsLinked to original sources

bioRxiv2020

Simultaneous orientation and 3D localization microscopy with a Vortex point spread function

We have developed an engineered Point Spread Function (PSF) to enable the simultaneous estimation of dipole orientation, 3D position and degree of rotational constraint of single-molecule emitters from a single 2D focal plane. Besides giving access to orientation information, the Vortex PSF along with the vectorial PSF fitter avoids localization bias common in localization microscopy for fixed dipole emitters. We demonstrate this technique on reorienting single-molecules and using binding-activated localization microscopy on DNA intercalators, corroborating perpendicular azimuthal angles to the DNA axis for in-plane emitters but find a non-uniform distribution as a function of the polar angle. The Vortex PSF is realized by an affordable glass phase mask and has a compact footprint that can easily be combined with localization microscopy techniques on rotationally constrained emitters.

molecular biology↗

bioRxiv2018

Photon count estimation in single-molecule localization microscopy

Recently, Franke, Sauer and van de Linde1 introduced a way to estimate the axial position of single-molecules (TRABI). To this end, they compared the detected photon count from a temporal radial-aperture-based intensity estimation to the estimated count from Gaussian point-spread function (PSF) fitting to the data. Empirically they found this photometric ratio to be around 0.7-0.8 close to focus and decreasing away from it. Here, we explain this reported but unexplained discrepancy and furthermore show that the photometric ratio as indicator for axial position is susceptible even to typical optical aberrations.

molecular biology↗

bioRxiv2018

Photon yield enhancement of red fluorophores at cryogenic temperatures

Single Molecule Localization Microscopy has become one of the most successful and widely applied methods of Super-resolution Fluorescence Microscopy. Its achievable resolution strongly depends on the number of detectable photons from a single molecule until photobleaching. By cooling a sample from room temperature down to liquid nitrogen temperatures, the photostability of dyes can be enhanced by more than 100 fold, which results in an improvement in localization precision greater than 10 times. Here, we investigate a variety of fluorescent dyes in the red spectral region, and we find an average photon yield between 3.5 {middle dot} 106 to 11 {middle dot} 106 photons before bleaching at liquid nitrogen temperatures, corresponding to a theoretical localization precision around 0.1 nm.

biophysics↗