Enhanced Hippocampal Long-Term Potentiation and Fear Memory in Btbd9 Mutant Mice

Polymorphisms in BTBD9 have recently been associated with higher risk of restless legs syndrome (RLS), a neurological disorder characterized by uncomfortable sensations in the legs at rest that are relieved by movement. The BTBD9 protein contains a BTB/POZ domain and a BACK domain, but its function is unknown. To elucidate its function and potential role in the pathophysiology of RLS, we generated a line of mutant Btbd9 mice derived from a commercial gene-trap embryonic stem cell clone. Btbd9 is the mouse homolog of the human BTBD9. Proteins that contain a BTB/POZ domain have been reported to be associated with synaptic transmission and plasticity. We found that Btbd9 is naturally expressed in the hippocampus of our mutant mice, a region critical for learning and memory. As electrophysiological characteristics of CA3-CA1 synapses of the hippocampus are well characterized, we performed electrophysiological recordings in this region. The mutant mice showed normal input-output relationship, a significant impairment in pre-synaptic activity, and an enhanced long-term potentiation. We further performed an analysis of fear memory and found the mutant mice had an enhanced cued and contextual fear memory. To elucidate a possible molecular basis for these enhancements, we analyzed proteins that have been associated with synaptic plasticity. We found an elevated level of dynamin 1, an enzyme associated with endocytosis, in the mutant mice. These results suggest the first identified function of Btbd9 as being involved in regulating synaptic plasticity and memory. Recent studies have suggested that enhanced synaptic plasticity, analogous to what we have observed, in other regions of the brain could enhance sensory perception similar to what is seen in RLS patients. Further analyses of the mutant mice will help shine light on the function of BTBD9 and its role in RLS

Negative feedback regulation of the ERK1/2 MAPK pathway

The extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinase (MAPK) signalling pathway regulates many cellular functions, including proliferation, differentiation, and transformation. To reliably convert external stimuli into specific cellular responses and to adapt to environmental circumstances, the pathway must be integrated into the overall signalling activity of the cell. Multiple mechanisms have evolved to perform this role. In this review, we will focus on negative feedback mechanisms and examine how they shape ERK1/2 MAPK signalling. We will first discuss the extensive number of negative feedback loops targeting the different components of the ERK1/2 MAPK cascade, specifically the direct posttranslational modification of pathway components by downstream protein kinases and the induction of de novo gene synthesis of specific pathway inhibitors. We will then evaluate how negative feedback modulates the spatiotemporal signalling dynamics of the ERK1/2 pathway regarding signalling amplitude and duration as well as subcellular localisation. Aberrant ERK1/2 activation results in deregulated proliferation and malignant transformation in model systems and is commonly observed in human tumours. Inhibition of the ERK1/2 pathway thus represents an attractive target for the treatment of malignant tumours with increased ERK1/2 activity. We will, therefore, discuss the effect of ERK1/2 MAPK feedback regulation on cancer treatment and how it contributes to reduced clinical efficacy of therapeutic agents and the development of drug resistance

Lateral forces on circularly polarizable particles near a surface

Optical forces allow manipulation of small particles and control of nanophotonic structures with light beams. While some techniques rely on structured light to move particles using field intensity gradients, acting locally, other optical forces can push particles on a wide area of illumination but only in the direction of light propagation. Here we show that spin orbit coupling, when the spin of the incident circularly polarized light is converted into lateral electromagnetic momentum, leads to a lateral optical force acting on particles placed above a substrate, associated with a recoil mechanical force. This counterintuitive force acts in a direction in which the illumination has neither a field gradient nor propagation. The force direction is switchable with the polarization of uniform, plane wave illumination, and its magnitude is comparable to other optical forces.This work has been supported, in part, by EPSRC (UK). A.V.Z. acknowledges support from the Royal Society and the Wolfson Foundation. N.E. acknowledges partial support from the US Office of Naval Research Multidisciplinary University Research Initiative Grant No. N00014-10-1-0942. A.M. acknowledges support from the Spanish Government (contract Nos TEC2011-28664-C02-02 and TEC2014-51902-C2-1-R).Rodríguez Fortuño, FJ.; Engheta, N.; Martínez Abietar, AJ.; Zayats, AV. (2015). Lateral forces on circularly polarizable particles near a surface. Nature Communications. 6(8799):1-7. https://doi.org/10.1038/ncomms9799S1768799Novotny, L. & Hecht, B. Principles of Nano-Optics Cambridge University Press (2011).Jackson, J. D. Classical Electrodynamics Wiley (1998).Ashkin, A. & Dziedzic, J. M. Optical levitation by radiation pressure. Appl. Phys. Lett. 19, 283 (1971).Ashkin, A. Acceleration and trapping of particles by radiation pressure. Phys. Rev. Lett. 24, 156–159 (1970).Omori, R., Kobayashi, T. & Suzuki, A. Observation of a single-beam gradient-force optical trap for dielectric particles in air. Opt. Lett. 22, 816–818 (1997).Ashkin, A., Dziedzic, J. M., Bjorkholm, J. E. & Chu, S. Observation of a single-beam gradient force optical trap for dielectric particles. Opt. Lett. 11, 288–290 (1986).Ashkin, A., Dziedzic, J. M. & Yamane, T. Optical trapping and manipulation of single cells using infrared laser beams. Nature 330, 769–771 (1987).Bagnato, V. S. et al. Continuous stopping and trapping of neutral atoms. Phys. Rev. Lett. 58, 2194–2197 (1987).Phillips, W. D. Nobel lecture: laser cooling and trapping of neutral atoms. Rev. Mod. Phys. 70, 721–741 (1998).Wang, M. M. et al. Microfluidic sorting of mammalian cells by optical force switching. Nat. Biotechnol. 23, 83–87 (2005).Dholakia, K. & Čižmár, T. Shaping the future of manipulation. Nat. Photon. 5, 335–342 (2011).Zhao, R., Zhou, J., Koschny, T., Economou, E. N. & Soukoulis, C. M. Repulsive Casimir force in chiral metamaterials. Phys. Rev. Lett. 103, 103602 (2009).Leonhardt, U. & Philbin, T. G. Quantum levitation by left-handed metamaterials. New J. Phys. 9, 254–254 (2007).Ginis, V., Tassin, P., Soukoulis, C. M. & Veretennicoff, I. Enhancing optical gradient forces with metamaterials. Phys. Rev. Lett. 110, 057401 (2013).Rodríguez-Fortuño, F. J., Vakil, A. & Engheta, N. Electric levitation using ɛ-near-zero metamaterials. Phys. Rev. Lett. 112, 033902 (2014).Grier, D. G. A revolution in optical manipulation. Nature 424, 810–816 (2003).Yang, X., Liu, Y., Oulton, R. F., Yin, X. & Zhang, X. Optical forces in hybrid plasmonic waveguides. Nano Lett. 11, 321–328 (2011).Oskooi, A., Favuzzi, P. A., Kawakami, Y. & Noda, S. Tailoring repulsive optical forces in nanophotonic waveguides. Opt. Lett. 36, 4638 (2011).Shalin, A. S., Ginzburg, P., Belov, P. A., Kivshar, Y. S. & Zayats, A. V. Nano-opto-mechanical effects in plasmonic waveguides. Laser Photon. Rev. 8, 131–136 (2014).Abajo, F. J. G., de, Brixner, T. & Pfeiffer, W. Nanoscale force manipulation in the vicinity of a metal nanostructure. J. Phys. B At. Mol. Opt. Phys. 40, S249–S258 (2007).Juan, M. L., Righini, M. & Quidant, R. Plasmon nano-optical tweezers. Nat. Photon. 5, 349–356 (2011).Beth, R. Mechanical detection and measurement of the angular momentum of light. Phys. Rev. 50, 115–125 (1936).Padgett, M. & Bowman, R. Tweezers with a twist. Nat. Photon. 5, 343–348 (2011).Liu, M., Zentgraf, T., Liu, Y., Bartal, G. & Zhang, X. Light-driven nanoscale plasmonic motors. Nat. Nanotechnol. 5, 570–573 (2010).Marston, P. L. & Crichton, J. H. Radiation torque on a sphere caused by a circularly-polarized electromagnetic wave. Phys. Rev. A 30, 2508–2516 (1984).Sokolov, I. V. The angular momentum of an electromagnetic wave, the Sadovski effect, and the generation of magnetic fields in a plasma. Phys. Uspekhi 34, 925–932 (1991).Wang, S. B. & Chan, C. T. Lateral optical force on chiral particles near a surface. Nat. Commun. 5, 3307 (2014).Hayat, A., Müller, J. P. B. & Capasso, F. Lateral chirality-sorting optical forces. doi:10.1073/pnas.1516704112 (2015).Bliokh, K. Y., Bekshaev, A. Y. & Nori, F. Extraordinary momentum and spin in evanescent waves. Nat. Commun. 5, 3300 (2014).Antognozzi, M. et al. Direct measurement of the extraordinary optical momentum using a nano-cantilever. Preprint at http://arxiv.org/abs/1506.04248 (2015).Bekshaev, A. Y., Bliokh, K. Y. & Nori, F. Transverse spin and momentum in two-wave interference. Phys. Rev. X 5, 011039 (2015).Bliokh, K. Y., Smirnova, D. & Nori, F. Quantum spin Hall effect of light. Science 348, 1448–1451 (2015).Rodríguez-Fortuño, F. J. et al. Near-field interference for the unidirectional excitation of electromagnetic guided modes. Science 340, 328–330 (2013).Kapitanova, P. V. et al. Photonic spin Hall effect in hyperbolic metamaterials for polarization-controlled routing of subwavelength modes. Nat. Commun. 5, 3226 (2014).Bliokh, K. Y., Rodríguez-Fortuño, F. J., Nori, F. & Zayats, A. V. Spin-orbit interactions of light. Preprint at http://arxiv.org/abs/1505.02864 (2015).O’Connor, D., Ginzburg, P., Rodríguez-Fortuño, F. J., Wurtz, G. A. & Zayats, A. V. Spin–orbit coupling in surface plasmon scattering by nanostructures. Nat. Commun. 5, 5327 (2014).Neugebauer, M., Bauer, T., Banzer, P. & Leuchs, G. Polarization tailored light driven directional optical nanobeacon. Nano Lett. 14, 2546–2551 (2014).Mueller, J. P. B. & Capasso, F. Asymmetric surface plasmon polariton emission by a dipole emitter near a metal surface. Phys. Rev. B 88, 121410 (2013).Xi, Z. et al. Controllable directive radiation of a circularly polarized dipole above planar metal surface. Opt. Express 21, 30327 (2013).Carbonell, J. et al. Directive excitation of guided electromagnetic waves through polarization control. Phys. Rev. B 89, 155121 (2014).Young, A. B. et al. Polarization engineering in photonic crystal waveguides for spin-photon entanglers. Phys. Rev. Lett. 115, 153901 (2015).Mitsch, R., Sayrin, C., Albrecht, B., Schneeweiss, P. & Rauschenbeutel, A. Quantum state-controlled directional spontaneous emission of photons into a nanophotonic waveguide. Nat. Commun. 5, 5713 (2014).Le Kien, F. & Rauschenbeutel, A. Anisotropy in scattering of light from an atom into the guided modes of a nanofiber. Phys. Rev. A 90, 023805 (2014).Luxmoore, I. J. et al. Interfacing spins in an InGaAs quantum dot to a semiconductor waveguide circuit using emitted photons. Phys. Rev. Lett. 110, 037402 (2013).Rodríguez-Fortuño, F. J. et al. Universal method for the synthesis of arbitrary polarization states radiated by a nanoantenna. Laser Photon. Rev. 8, L27–L31 (2014).Rodríguez-Fortuño, F. J., Barber-Sanz, I., Puerto, D., Griol, A. & Martinez, A. Resolving light handedness with an on-chip silicon microdisk. ACS Photon. 1, 762–767 (2014).Petersen, J., Volz, J. & Rauschenbeutel, A. Chiral nanophotonic waveguide interface based on spin-orbit interaction of light. Science 346, 67–71 (2014).Xi, Z., Lu, Y., Yu, W., Wang, P. & Ming, H. Unidirectional surface plasmon launcher: rotating dipole mimicked by optical antennas. J. Opt. 16, 105002 (2014).Frisch, R. Experimental demonstration of Einstein’s radiation recoil. Zeitschrift für Phys. 86, 42–45 (1933).Wylie, J. M. & Sipe, J. E. Quantum electrodynamics near an interface. II. Phys. Rev. A 32, 2030–2043 (1985).Fichet, M., Schuller, F., Bloch, D. & Ducloy, M. van der Waals interactions between excited-state atoms and dispersive dielectric surfaces. Phys. Rev. A 51, 1553–1564 (1995).Failache, H., Saltiel, S., Fichet, M., Bloch, D. & Ducloy, M. Resonant van der Waals repulsion between excited Cs atoms and sapphire surface. Phys. Rev. Lett. 83, 5467–5470 (1999).Gordon, J. P. & Ashkin, A. Motion of atoms in a radiation trap. Phys. Rev. A 21, 1606–1617 (1980).Chaumet, P. C. & Nieto-Vesperinas, M. Time-averaged total force on a dipolar sphere in an electromagnetic field. Opt. Lett. 25, 1065–1067 (2000).Ishimaru, A. Electromagnetic Wave Propagation, Radiation, and Scattering Prentice Hall (1990).Söllner, I., Mahmoodian, S., Javadi, A. & Lodahl, P. A chiral spin-photon interface for scalable on-chip quantum-information processing. Preprint at http://arxiv.org/abs/1406.4295 (2014).Rotenberg, N. et al. Magnetic and electric response of single subwavelength holes. Phys. Rev. B Condens. Matter Mater. Phys. 88, 241408 (2013).Sukhov, S., Kajorndejnukul, V. & Dogariu, A. Dynamic Consequences of Optical Spin-Orbit Interaction. Preprint at http://arxiv.org/abs/1504.01766 (2015).Scheel, S., Buhmann, S. Y., Clausen, C. & Schneeweiss, P. Directional spontaneous emission and lateral Casimir-Polder force on an atom close to a nanofiber. Preprint at http://arxiv.org/abs/1505.01275 (2015).Rodríguez-Fortuño, F. J., Engheta, N., Martínez, A. & Zayats, A. V. Lateral Forces Acting on Particles Near a Surface Under Circularly Polarized Illumination. in 5th Inte rnational Topical Meeting on Nanophotonics and Metamaterials (Nanometa) (2-914771-91-6, Seefeld, Austria 2015).Bochenkov, V. et al. Applications of plasmonics: general discussion. Faraday Discuss. 178, 435–466 (2015).Dogariu, A. & Schwartz, C. Conservation of angular momentum of light in single scattering. Opt. Express 14, 8425–8433 (2006).Haefner, D., Sukhov, S. & Dogariu, A. Spin hall effect of light in spherical geometry. Phys. Rev. Lett. 102, 123903 (2009).Bliokh, K. Y. et al. Spin-to-orbit angular momentum conversion in focusing, scattering, and imaging systems. Opt. Express 19, 26132–26149 (2011)

The High-Order Toroidal Moments and Anapole States in All-Dielectric Photonics

All-dielectric nanophotonics attracts ever increasing attention nowadays due to the possibility of controlling and configuring light scattering on high-index semiconductor nanoparticles. It opens a room of opportunities for designing novel types of nanoscale elements and devices, and paves the way for advanced technologies of light energy manipulation. One of the exciting and promising prospects is associated with utilizing the so-called toroidal moment, being the result of poloidal currents excitation, and anapole states, corresponding to the interference of dipole and toroidal electric moments. Here, higher-order toroidal moments of both types (up to the electric octupole toroidal moment) are presented and investigated in detail via the direct Cartesian multipole decomposition allowing new near- and far-field configurations to be obtained. Poloidal currents can be associated with vortex-like distributions of the displacement currents inside nanoparticles, revealing the physical meaning of the high-order toroidal moments and the convenience of the Cartesian multipoles as an auxiliary tool for analysis. High-order nonradiating anapole states accompanied by the excitation of intense near-fields are demonstrated. It is believed that the results are of high importance for both the fundamental understanding of light scattering by high-index particles and a variety of nanophotonics applications and light governing on nanoscale

Theory, observation, and ultrafast response of the hybrid anapole regime in light scattering

Modern nanophotonics has witnessed the rise of "electric anapoles" (EDAs), destructive interferences of electric and toroidal electric dipoles, actively exploited to resonantly decrease radiation from nanoresonators. However, the inherent duality in Maxwell equations suggests the intriguing possibility of "magnetic anapoles," involving a nonradiating composition of a magnetic dipole and a magnetic toroidal dipole. Here, a hybrid anapole (HA) of mixed electric and magnetic character is predicted and observed experimentally via dark field spectroscopy, with all the dominant multipoles being suppressed by the toroidal terms in a nanocylinder. Breaking the spherical symmetry allows to overlap up to four anapoles stemming from different multipoles with just two tuning parameters. This effect is due to a symmetry-allowed connection between the resonator multipolar response and its eigenstates. The authors delve into the physics of such current configurations in the stationary and transient regimes and explore new ultrafast phenomena arising at sub-picosecond timescales, associated with the HA dynamics. The theoretical results allow the design of non-Huygens metasurfaces featuring a dual functionality: perfect transparency in the stationary regime and controllable ultrashort pulse beatings in the transient. Besides offering significant advantages with respect to EDAs, HAs can play an essential role in developing the emerging field of ultrafast resonant phenomena

‘Photonic Hook’ based optomechanical nanoparticle manipulator

Abstract Specialized electromagnetic fields can be used for nanoparticle manipulation along a specific path, allowing enhanced transport and control over the particle’s motion. In this paper, we investigate the optical forces produced by a curved photonic jet, otherwise known as the “photonic hook”, created using an asymmetric cuboid. In our case, this cuboid is formed by appending a triangular prism to one side of a cube. A gold nanoparticle immersed in the cuboid’s transmitted field moves in a curved trajectory. This result could be used for moving nanoparticles around obstacles; hence we also consider the changes in the photonic hook’s forces when relatively large glass and gold obstacles are introduced at the region where the curved photonic jet is created. We show, that despite the obstacles, perturbing the field distribution, a particle can move around glass obstacles of a certain thickness. For larger glass slabs, the particle will be trapped stably near it. Moreover, we noticed that a partial obstruction of the photonic jet’s field using the gold obstacle results in a complete disruption of the particle’s trajectory

Information storage and retrieval in a single levitating colloidal particle

The binary switch is a basic component of digital information. From phase-change alloys to nanomechanical beams, molecules and atoms, new strategies for controlled bistability hold great interest for emerging technologies. We present a generic methodology for precise and parallel spatiotemporal control of nanometre-scale matter in a fluid, and demonstrate the ability to attain digital functionalities such as switching, gating and data storage in a single colloid, with further implications for signal amplification and logic operations. This fluid-phase bit can be arrayed at high densities, manipulated by either electrical or optical fields, supports low-energy, high-speed operation and marks a first step toward ‘colloidal information’. The principle generalizes to any system where spatial perturbation of a particle elicits a differential response amenable to readout