News: (Update) miCube: Rethinking modular fluorescence microscopy

Hurrah, we finalised the design of our miCube (V0.1)! Details can be found [here] and include part numbers, CAD-drawings and STL files for CNC machining/milling or 3D printing published under a Creative Common license. Big shout out to Sander Baas and Koen Martens. If you have any questions, remarks or ideas, please feel to contact me.

Posted in miCube, news, open access

News: Congratulations to Shazia and welcome to Sander…

Congratulations to Shazia Farooq for successfully defending her PhD thesis titled “Studying fast dynamics in biological complexes: from photosynthesis in vivo to single DNA molecules in vitro” [link]. Well done and thanks to all the helpers for the great party afterwards!

Already a few weeks ago, Sander Baas joined our lab for his Master’s thesis to set up three-dimensional super-resolution microscopy. Looks very promising!

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Publication: A single-molecule FRET sensor for monitoring DNA synthesis in real time

C. Fijen, A. Montón Silva, A. Hochkoeppler and J. Hohlbein, Physical Chemistry Chemical Physics, 19, 4222-4230, 2017, [link]

fig1We developed a versatile DNA assay and framework for monitoring polymerization of DNA in real time and at the single-molecule level. The assay consists of an acceptor labelled DNA primer annealed to a DNA template that is labelled on its single stranded, downstream overhang with a donor fluorophore. Upon extension of the primer using a DNA polymerase, the overhang of the template alters its conformation from a random coil to the canonical structure of double stranded DNA. This conformational change increases the distance between the donor and the acceptor fluorophore and can be detected as a decrease in the Förster resonance energy transfer (FRET) efficiency between both fluorophores. Remarkably, the DNA assay does not require any modification of the DNA polymerase and albeit the simple and robust spectroscopic readout facilitates measurements even with conventional fluorimeters or stopped-flow equipment, single-molecule FRET provides additional access to parameters such as the processivity of DNA synthesis and, for one of the three DNA polymerases tested, the detection of binding and dissociation of the DNA polymerase to DNA. We furthermore demonstrate that primer extensions by a single base can be resolved.

Posted in published

Publication: Visualization of BRI1 and SERK3/BAK1 Nanoclusters in Arabidopsis Roots

S.J. Hutten, D.S. Hamers, M.A. an den Toorn, W. van Esse, A. Nolles, C.A. Bücherl, S.C. de Vries, J. Hohlbein, J.W. Borst, PLoS ONE 12(1): e0169905, 2017, [link]


Brassinosteroids (BRs) are plant hormones that are perceived at the plasma membrane (PM) by the ligand binding receptor BRASSINOSTEROID-INSENSITIVE1 (BRI1) and the co-receptor SOMATIC EMBRYOGENESIS RECEPTOR LIKE KINASE 3/BRI1 ASSOCIATED KINASE 1 (SERK3/BAK1). To visualize BRI1-GFP and SERK3/BAK1-mCherry in the plane of the PM, variable-angle epifluorescence microscopy (VAEM) was employed, which allows selective illumination of a thin surface layer. VAEM revealed an inhomogeneous distribution of BRI1-GFP and SERK3/BAK1-mCherry at the PM, which we attribute to the presence of distinct nanoclusters. Neither the BRI1 nor the SERK3/BAK1 nanocluster density is affected by depletion of endogenous ligands or application of exogenous ligands. To reveal interacting populations of receptor complexes, we utilized selective-surface observation—fluorescence lifetime imaging microscopy (SSO-FLIM) for the detection of Förster resonance energy transfer (FRET). Using this approach, we observed hetero-oligomerisation of BRI1 and SERK3 in the nanoclusters, which did not change upon depletion of endogenous ligand or signal activation. Upon ligand application, however, the number of BRI1-SERK3 /BAK1 hetero-oligomers was reduced, possibly due to endocytosis of active signalling units of BRI1-SERK3/BAK1 residing in the PM. We propose that formation of nanoclusters in the plant PM is subjected to biophysical restraints, while the stoichiometry of receptors inside these nanoclusters is variable and important for signal transduction.

Posted in open access, published

News: Welcome to Charlotte Westbroek…

…who joins the group for her MSc thesis. In collaboration with the group of Food Process Engineering (Prof. Atze Jan van der Groot), Charlotte will explore a variety of fluorescence based techniques to image meat replacers.

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miCube V0.1: first tests

We finally managed to perform some test experiments and it is looking very promising! We tracked small fluorescent quantum dots (< 5 nm diameter) diffusing in water (20% glycerol) and we were happy to learn that even for such a demanding application new sCMOS-based cameras are doing just fine. Here a picture of the current assembly. More soon!


Posted in miCube

News: Welcome to Jan Groen…

…who joins the group for his MSc thesis. In collaboration with the group of Stan Brouns (now Delft, previously WUR) he will enzymatically modify DNA to allow the labelling with fluorescent dyes and then image the labelled DNA in vivo and in vitro using super-resolution microscopy.

Posted in news