| 1. |
- Molin, Mikael, 1973, et al.
(författare)
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Protein kinase A controls yeast growth in visible light
- 2020
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Ingår i: BMC Biology. - : Springer Science and Business Media LLC. - 1741-7007. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: A wide variety of photosynthetic and non-photosynthetic species sense and respond to light, having developed protective mechanisms to adapt to damaging effects on DNA and proteins. While the biology of UV light-induced damage has been well studied, cellular responses to stress from visible light (400–700 nm) remain poorly understood despite being a regular part of the life cycle of many organisms. Here, we developed a high-throughput method for measuring growth under visible light stress and used it to screen for light sensitivity in the yeast gene deletion collection. Results: We found genes involved in HOG pathway signaling, RNA polymerase II transcription, translation, diphthamide modifications of the translational elongation factor eEF2, and the oxidative stress response to be required for light resistance. Reduced nuclear localization of the transcription factor Msn2 and lower glycogen accumulation indicated higher protein kinase A (cAMP-dependent protein kinase, PKA) activity in many light-sensitive gene deletion strains. We therefore used an ectopic fluorescent PKA reporter and mutants with constitutively altered PKA activity to show that repression of PKA is essential for resistance to visible light. Conclusion: We conclude that yeast photobiology is multifaceted and that protein kinase A plays a key role in the ability of cells to grow upon visible light exposure. We propose that visible light impacts on the biology and evolution of many non-photosynthetic organisms and have practical implications for how organisms are studied in the laboratory, with or without illumination.
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| 2. |
- Andrén, Daniel, 1991, et al.
(författare)
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Large-Scale Metasurfaces Made by an Exposed Resist
- 2020
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 7:4, s. 885-892
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Tidskriftsartikel (refereegranskat)abstract
- Phase-gradient metasurfaces have the potential to revolutionize photonics by offering ultrathin alternatives to a wide range of common optical elements, including bulky refractive optics, waveplates, and axicons. However, the fabrication of state-of-the-art metasurfaces typically involves several expensive, time-consuming, and potentially hazardous processing steps. To address this limitation, a facile methodology to construct phase-gradient metasurfaces from an exposed standard electron beam resist is developed. The method dramatically cuts the required processing time and cost as well as reduces safety hazards. The advantages of the method are demonstrated by constructing high-performance flat optics based on the Pancharatnam-Berry phase gradient concept for the entire visible wavelength range. Manufactured devices include macroscopic (1 cm diameter) positive lenses, gratings exhibiting anomalous reflection, and cylindrical metalenses on flexible plastic substrates.
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| 3. |
- Andrén, Daniel, 1991, et al.
(författare)
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Metasurfaces for Divergent Beams and Large-Area Metasurfaces
- 2021
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Ingår i: International Conference on Metamaterials, Photonic Crystals and Plasmonics. - 2429-1390. ; , s. 517-518
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Konferensbidrag (refereegranskat)abstract
- We will give an overview of our recent work on the design and fabrication of metasurfaces, i.e., dense arrays of subwavelength-sized scatterers (meta-atoms) designed in shape, size, position, and orientation. First, we have developed simulation strategies for large-scale metasurfaces and metasurfaces for strongly divergent beams. Second, we have developed a facile fabrication technique based on an exposed resist to build large-scale metasurfaces. These novel computational and fabrication techniques allow us to achieve metasurfaces with unprecedented functionality.
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| 4. |
- Andrén, Daniel, 1991, et al.
(författare)
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Microscopic metavehicles powered and steered by embedded optical metasurfaces
- 2021
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Ingår i: Nature Nanotechnology. - : Springer Science and Business Media LLC. - 1748-3387 .- 1748-3395. ; 16:9, s. 970-974
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured dielectric metasurfaces offer unprecedented opportunities to manipulate light by imprinting an arbitrary phase gradient on an impinging wavefront(1). This has resulted in the realization of a range of flat analogues to classical optical components, such as lenses, waveplates and axicons(2-6). However, the change in linear and angular optical momentum(7) associated with phase manipulation also results in previously unexploited forces and torques that act on the metasurface itself. Here we show that these optomechanical effects can be utilized to construct optical metavehicles-microscopic particles that can travel long distances under low-intensity plane-wave illumination while being steered by the polarization of the incident light. We demonstrate movement in complex patterns, self-correcting motion and an application as transport vehicles for microscopic cargoes, which include unicellular organisms. The abundance of possible optical metasurfaces attests to the prospect of developing a wide variety of metavehicles with specialized functional behaviours.
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| 5. |
- Baranov, Denis, 1990, et al.
(författare)
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Circular dichroism mode splitting and bounds to its enhancement with cavity-plasmon-polaritons
- 2020
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Ingår i: Nanophotonics. - : Walter de Gruyter GmbH. - 2192-8614. ; 9:2, s. 283-293
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Tidskriftsartikel (refereegranskat)abstract
- Geometrical chirality is a widespread phenomenon that has fundamental implications for discriminating enantiomers of biomolecules. In order to enhance the chiral response of the medium, it has been suggested to couple chiral molecules to resonant optical cavities in order to enhance the circular dichroism (CD) signal at the resonant frequency of the cavity. Here, we studied a distinctly different regime of chiral light-matter interaction, wherein the CD signal of a chiral medium splits into polaritonic modes by reaching the strong coupling regime with an optical microcavity. Specifically, we show that by strongly coupling chiral plasmonic nanoparticles to a non-chiral Fabry-Pérot microcavity one can imprint the mode splitting on the CD spectrum of the coupled system and thereby effectively shift the initial chiral resonance to a different energy. We first examined the effect with the use of analytical transfer-matrix method as well as numerical finite-difference time-domain (FDTD) simulations. Furthermore, we confirmed the validity of theoretical predictions in a proof-of-principle experiment involving chiral plasmonic nanoparticles coupled to a Fabry-Pérot microcavity.
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| 6. |
- Cui, Ximin, 1991, et al.
(författare)
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Synchronization of optically self-assembled nanorotors
- 2024
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of nanoparticles by means of interparticle optical forces provides a compelling approach toward contact-free organization and manipulation of nanoscale entities. However, exploration of the rotational degrees of freedom in this process has remained limited, primarily because of the predominant focus on spherical nanoparticles, for which individual particle orientation cannot be determined. Here, we show that gold nanorods, which self-assemble in water under the influence of circularly polarized light, exhibit synchronized rotational motion at kilohertz frequencies. The synchronization is caused by strong optical interactions and occurs despite the presence of thermal diffusion. Our findings elucidate the intricate dynamics arising from the transfer of photon spin angular momentum to optically bound matter and hold promise for advancing the emerging field of light-driven nanomachinery.
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| 7. |
- Dara, Pantea, 1994, et al.
(författare)
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Directional Control of Transient Flows Generated by Thermoplasmonic Bubble Nucleation
- 2023
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Ingår i: Journal of Physical Chemistry C. - 1932-7447 .- 1932-7455. ; 127:35, s. 17454-17459
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been shown that strong flow transients, reaching mm/s flow speeds, are induced when microscopic vapor bubbles nucleate on spatially isolated laser-heated plasmonic nanoantennas supported on a substrate. However, the flow pattern is cylindrically symmetric and always directed toward the nanoantenna at the substrate plane. This limits its applicability in, for example, particle manipulation schemes. Here, we show that the flow direction can be locally reversed by breaking the photothermal symmetry using two nearby nanoantennas that differ either in size or polarization response. The in-plane flow transient is strong enough to push microparticles tens of microns across a surface. Directional flow control may provide the means for rapid and precise mass transport near surfaces for applications in microfluidics, bionanotechnology, and particle sorting.
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| 8. |
- Green, Thomas D, 1984, et al.
(författare)
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Optical material anisotropy in high-index transition metal dichalcogenide Mie nanoresonators
- 2020
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Ingår i: Optica. - 2334-2536. ; 7:6, s. 680-686
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Tidskriftsartikel (refereegranskat)abstract
- Resonant optical antennas provide unprecedented opportunities to control light on length scales far below the diffraction limit. Recent studies have demonstrated that nanostructures made of multilayer transition metal dichalcogenides (TMDCs) can exhibit well-defined and intense Mie resonances in the visible to the near-infrared spectral range. These resonances are realizable because the TMDC materials exhibit very high in-plane refractive indices, in fact higher than what is found in typical high-index dielectric materials like Si orGaAs. However, their out-of-plane refractive indices are comparatively low. Here we experimentally and theoretically investigate how this unusually large material anisotropy influences the optical response of individual TMDC nanoresonators made of MoS2. We find that anisotropy strongly affects the far-field optical response of the resonators, as well as complex interference effects, such as anapole and resonant Kerker conditions. Moreover, we show that it is possible to utilize the material anisotropy to probe the vectorial nature of the nanoresonator internal near fields. Specifically, we show that Raman spectra originating from individual MoS2 nanoresonators exhibit mode-specific anisotropic enhancement factors that vary with the nanoresonator size and correlate with specific modes supported at resonance. Our study indicates that exploring material anisotropy in novel high-index dielectrics may lead to new nanophotonic effects and applications. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 9. |
- Jones, Steven, 1990, et al.
(författare)
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Strong Transient Flows Generated by Thermoplasmonic Bubble Nucleation
- 2020
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 14:12, s. 17468-17475
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Tidskriftsartikel (refereegranskat)abstract
- The challenge of inducing and controlling localized fluid flows for generic force actuation and for achieving efficient mass transport in microfluidics is key to the development of next-generation miniaturized systems for chemistry and life sciences. Here we demonstrate a methodology for the robust generation and precise quantification of extremely strong flow transients driven by vapor bubble nucleation on spatially isolated plasmonic nanoantennas excited by light. The system is capable of producing peak flow speeds of the order mm/s at modulation rates up to ∼100 Hz in water, thus allowing for a variety of high-throughput applications. Analysis of flow dynamics and fluid viscosity dependence indicates that the transient originates in the rapid bubble expansion that follows nucleation rather than being strictly thermocapillary in nature.
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| 10. |
- Juhlin, Lars, et al.
(författare)
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Selective surface-enhanced Raman scattering detection of Tabun, VX and Cyclosarin nerve agents using 4-pyridine amide oxime functionalized gold nanopillars
- 2020
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 211
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Tidskriftsartikel (refereegranskat)abstract
- We have earlier demonstrated sensitive detection of low the volatile nerve agents Tabun, Cyclosarin and VX by using handheld Raman instrumentation in conjunction with surface-enhanced Raman scattering (SERS) attained with gold and silver coated Si nanopillar substrates. In the present proof-of-concept study, the gold substrates chemically are functionalized to realize selectivity towards organophosphorus compounds (OPs) with high sensitivity. A potential capturer and reporter molecule, chemical nerve agent antidote, 4-pyridine amide oxime, is evaluated due to its high Raman cross section, high chemical affinity towards gold, and binding specificity to the target substances Tabun, VX and Cyclosarin via the oxime group. Upon selective and covalent binding, the SERS probe undergoes structural changes which are reflected in the spectral SERS responses, making it suitable for indirect monitoring of nerve agents in aqueous solution. With the probe attached to the hotspots of Au-coated Si nanopillars, the SERS signals distinctly discriminate between specific and non-specific analyte binding of Tabun, Cyclosarin and VX down to sub ppm levels. SERS spectrum of 4-PAO is measured after microliter drop coating of aqueous sample solution onto the functionalized substrates and subsequent water evaporation from surfaces. This binding assay is complemented by letting functionalized substrates being immersed into sample solutions 1 h before measuring. Binding specific SERS response decreases in following order: Tabun > VX > Cyclosarin. Overall, the concept looks promising, as expected the candidate probe 4-PAO introduces selectivity to the nanopillar gold substrates without loss of sensitivity.
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