arXiv subjects

Johannes Hohlbein

Publications and source records attributed to Johannes Hohlbein.

3 recordsLinked to original sources

arXiv2025

Viscophoretic particle transport

Viscosity is a fundamental property of liquids and determines the diffusivity of suspended particles. A gradient in viscosity leads to a gradient in diffusivity, yet it is unknown whether such a gradient can lead to directed transport of particles. In this work, we generate a steep, stable viscosity gradient in a microfluidic channel and image the resulting transport of suspended nanoparticles at the single-particle level using high-resolution microscopy. We observe high viscophoretic drift velocities that significantly exceed theoretical predictions. In addition, we utilize viscophoresis for a new type of particle trap. We provide a first quantification of a transport phenomenon that is of importance in any system and any application exhibiting viscosity gradients, for example in separation using membrane technology as well as in inter- and intracellular biomolecular transport.

physics.flu-dyn↗

arXiv2021

Open microscopy in the life sciences: Quo Vadis?

Light microscopy allows observing cellular features and objects with sub-micrometer resolution. As such, light microscopy has been playing a fundamental role in the life sciences for more than a hundred years. Fueled by the availability of mass-produced electronics and hardware, publicly shared documentation and building instructions, open-source software, wide access to rapid prototyping and 3D printing, and the enthusiasm of contributors and users involved, the concept of open microscopy has been gaining incredible momentum, bringing new sophisticated tools to an expanding user base. Here, we will first discuss the ideas behind open science and open microscopy before highlighting recent projects and developments in open microscopy. We argue that the availability of well-designed open hardware and software solutions targeting broad user groups or even non-experts, will increasingly be relevant to cope with the increasing complexity of cutting-edge imaging technologies. We will then extensively discuss the current and future challenges of open microscopy.

q-bio.OT↗

arXiv2017

Precision and accuracy of single-molecule FRET measurements - a worldwide benchmark study

Single-molecule Förster resonance energy transfer (smFRET) is increasingly being used to determine distances, structures, and dynamics of biomolecules in vitro and in vivo. However, generalized protocols and FRET standards ensuring both the reproducibility and accuracy of measuring FRET efficiencies are currently lacking. Here we report the results of a worldwide, comparative, blind study, in which 20 labs determined the FRET efficiencies of several dye-labeled DNA duplexes. Using a unified and straightforward method, we show that FRET efficiencies can be obtained with a standard deviation between $Δ$E = +-0.02 and +-0.05. We further suggest an experimental and computational procedure for converting FRET efficiencies into accurate distances. We discuss potential uncertainties in the experiment and the modelling. Our extensive quantitative assessment of intensity-based smFRET measurements and correction procedures serve as an essential step towards validation of distance networks with the ultimate aim to archive reliable structural models of biomolecular systems obtained by smFRET-based hybrid methods.

q-bio.QM↗