Universiteit Leiden

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New funding for advanced microscopy using gold nanorods

A consortium of researchers from the Leiden Institute of Physics (LION), the Institute of Biology Leiden (IBL), and the Leiden Institute of Chemistry (LIC) received a FOM program grant to develop a novel way of studying individual proteins inside a cell using gold nanorods.

Dr. John van Noort (LION), Prof. Dr. Michel Orrit (LION), Dr. Alexander Kros (LIC) and Dr. Marcel Schaaf (IBL) received a FOM program grant (1.4 M€) for a project in which gold nanorods will be tagged to proteins inside living cells in order to study their function. This multidisciplinary project, which integrates chemical, physical, and biological expertise of the Science Faculty of Leiden University, is entitled ‘Single gold nanorods in live cells’.

How does it work?

With GFP-labeled proteins it is possible to image individual molecules inside living cells and study their dynamic behavior. However, due to the limited stability of the fluorescence of these proteins they can only be followed for about half a second. A solution to this problem is labeling proteins with tiny gold particles of approximately 40 nm in length, so-called gold nanorods. These rods can emit very bright optical signals that do not blink or bleach and are stable for long periods of time. This way, it will be possible to locate individual proteins inside a cell with very high (~10 nm) accuracy, and follow them for hours, enabling the study of a wide array of dynamic cellular processes at the single-molecule level. In addition to the imaging of gold nanorods inside cells, it is also possible to ‘trap’ these particles using focused laser light. With this technique local forces and torques that proteins experience inside cells can be measured.

The gold nanorods will be synthesized in the group of Dr. Alexander Kros (LIC), where they will be functionalized in such a way that they can be tagged to specifically labeled proteins in living cells. Imaging and tracking will be performed in the group of Dr. John van Noort (LION) using a specialized two-photon-luminescence setup. The trapping and further characterization of the gold nanorods will be done in the laboratory of Prof. Dr. Michel Orrit (LION).

Within the IBL, Dr. Marcel Schaaf will apply the developed technology to image and track individual glucocorticoid receptors. These receptors mediate the effects of the stress hormone cortisol and synthetic analogs of this hormone like prednisone and dexamethasone which are widely used as anti-inflammatory drugs. They act as transcription factors, which means that they bind to specific target sequences in the genome and thereby regulate transcription of a nearby gene. Using the gold nanorod technology it will be studied how glucocorticoid receptors find their target sequence, how (long) it binds to this sequence and what happens to a receptor after this binding event.

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