by Keyword: Light

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Tian, X., De Pace, C., Ruiz-Perez, L., Chen, B., Su, R., Zhang, M., Zhang, R., Zhang, Q., Wang, Q., Zhou, H., Wu, J., Zhang, Z., Tian, Y., Battaglia, G., (2020). A Cyclometalated iridium (III) complex as a microtubule probe for correlative super-resolution fluorescence and electron microscopy Advanced Materials 32, (39), 2003901

The visualization of microtubules by combining optical and electron microscopy techniques provides valuable information to understand correlated intracellular activities. However, the lack of appropriate probes to bridge both microscopic resolutions restricts the areas and structures that can be comprehended within such highly assembled structures. Here, a versatile cyclometalated iridium (III) complex is designed that achieves synchronous fluorescence–electron microscopy correlation. The selective insertion of the probe into a microtubule triggers remarkable fluorescence enhancement and promising electron contrast. The long-life, highly photostable probe allows live-cell super-resolution imaging of tubulin localization and motion with a resolution of ≈30 nm. Furthermore, correlative light–electron microscopy and energy-filtered transmission electron microscopy reveal the well-associated optical and electron signal at a high specificity, with an interspace of ≈41 Å of microtubule monomer in cells.

Keywords: Correlation light–electron microscopy, Microtubules, Organometallic probes, Super-resolution microscopy

Wang, Xu, Sridhar, Varun, Guo, Surong, Talebi, Nahid, Miguel-López, Albert, Hahn, Kersten, van Aken, Peter A., Sánchez, Samuel, (2018). Fuel-free nanocap-like motors actuated under visible light Advanced Functional Materials 28, (25), 1705862

The motion of nanomotors triggered by light sources will provide new alternative routes to power nanoarchitectures without the need of chemical fuels. However, most light-driven nanomotors are triggered by UV-light, near infrared reflection, or laser sources. It is demonstrated that nanocap shaped Au/TiO2 nanomotors (175 nm in diameter) display increased Brownian motion in the presence of broad spectrum visible light. The motion results from the surface plasmon resonance effect leading to self-electrophoresis between the Au and TiO2 layers, a mechanism called plasmonic photocatalytic effect in the field of photocatalysis. This mechanism is experimentally characterized by electron energy loss spectroscopy, energy-filtered transmission electron microscopy, and optical video tracking. This mechanism is also studied in a more theoretical manner using numerical finite-difference time-domain simulations. The ability to power nanomaterials with visible light may result in entirely new applications for externally powered micro/nanomotors.

Keywords: Enhanced Brownian motion, Fuel-free nanomotors, Nanomachines, Self-electrophoresis, Visible light

Izquierdo-Serra, Mercè, Trauner, Dirk, Llobet, Artur, Gorostiza, Pau, (2013). Optical control of calcium-regulated exocytosis Biochimica et Biophysica Acta (BBA) - General Subjects , 1830, (3), 2853-2860

Background Neurons signal to each other and to non-neuronal cells as those in muscle or glands, by means of the secretion of neurotransmitters at chemical synapses. In order to dissect the molecular mechanisms of neurotransmission, new methods for directly and reversibly triggering neurosecretion at the presynaptic terminal are necessary. Here we exploit the calcium permeability of the light-gated channel LiGluR in order to reversibly manipulate cytosolic calcium concentration, thus controlling calcium-regulated exocytosis. Methods Bovine chromaffin cells expressing LiGluR were stimulated with light. Exocytic events were detected by amperometry or by whole-cell patch-clamp to quantify membrane capacitance and calcium influx. Results Amperometry reveals that optical stimulation consistently triggers exocytosis in chromaffin cells. Secretion of catecholamines can be adjusted between zero and several Hz by changing the wavelength of illumination. Differences in secretion efficacy are found between the activation of LiGluR and native voltage-gated calcium channels (VGCCs). Our results show that the distance between sites of calcium influx and vesicles ready to be released is longer when calcium influx is triggered by LiGluR instead of native VGCCs. Conclusion and general significance LiGluR activation directly and reversibly increases the intracellular calcium concentration. Light-gated calcium influx allows for the first time to control calcium-regulated exocytosis without the need of applying depolarizing solutions or voltage clamping in chromaffin cells. Thus, LiGluR is a useful tool to study the secretory mechanisms and their spatiotemporal patterns in neurotransmission, and opens a window to study other calcium-dependent processes such as muscular contraction or cell migration.

Keywords: Optical control, Calcium, Exocytosis, Light-gated glutamate receptor (LiGluR), Neurotransmission, Optogenetics

Gorostiza, P., Isacoff, E. Y., (2008). Optical switches for remote and noninvasive control of cell signaling Science 322, (5900), 395-399

Although the identity and interactions of signaling proteins have been studied in great detail, the complexity of signaling networks cannot be fully understood without elucidating the timing and location of activity of individual proteins. To do this, one needs a means for detecting and controlling specific signaling events. An attractive approach is to use light, both to report on and control signaling proteins in cells, because light can probe cells in real time with minimal damage. Although optical detection of signaling events has been successful for some time, the development of the means for optical control has accelerated only recently. Of particular interest is the development of chemically engineered proteins that are directly sensitive to light.

Keywords: Ion channels, Acetylcholine receptor, Glutamate-receptor, Potassium channel, K+ channel, Light, Neurons, Channelrhodopsin-2, Manipulation, Activation