[The role and mechanism of leucyl-tRNA synthetase in the regulation of protein synthesis in aging skeletal muscle].

The imbalance of protein metabolism is the major cause of skeletal muscle atrophy, and the decrease of protein synthesis directly leads to the occurrence and development of age-related sarcopenia. The canonical role of leucyl-tRNA synthetase (LeuRS) is ligating leucine to the cognate tRNA, and thus it plays a central role in genetic coding. With the further studies of LeuRS in recent years, LeuRS has been found to control protein homeostasis in aging skeletal muscle via its non-canonical role. In this paper, we reviewed the structure and biological features of aminoacyl-tRNA synthetase and LeuRS, and summarized the recent advances in studies on the effects of LeuRS in regulating aging skeletal muscle protein synthesis as an intracellular leucine sensor. Moreover, we also analyzed the potential role of LeuRS in activation of mammalian target of rapamycin complex 1 (mTORC1) signaling transduction pathway in response to anabolic stimuli such as exercise and amino acids ingestion. This paper may provide some new ideas for the prevention, diagnosis and treatment of age-related sarcopenia.

Strong Localization of Surface Plasmon Polaritons with Engineered Disorder.

In this work, we experimentally demonstrate for the first time strong localization of surface plasmon polaritons (SPPs) at visible regime in metallic nanogratings with short-range correlated disorder. By increasing the degree of disorder, the confinement of SPPs is significantly enhanced, and the effective SPP propagation length dramatically shrinks. Strong localization of SPPs eventually emerges at visible regime, which is verified by the exponentially decayed fields and the vanishing autocorrelation function of the SPPs. Physically, the short-range correlated disorder induces strong interference among multiple scattered SPPs and provides an adequate fluctuation to effective permittivity, which leads to the localization effect. Our study demonstrates a unique opportunity for disorder engineering to manipulate light on nanoscale and may achieve various applications in random nanolasing, solar energy, and strong light-matter interactions.

Mycobacterium marinum Infection in Zebrafish and Microglia Imitates the Early Stage of Tuberculous Meningitis.

Mycobacterium tuberculosis (M. tuberculosis) invading and activating microglia causes the most serious subtypes of tuberculosis called tubercular meningitis. However, the developmental process of tubercular meningitis, especially the early phase, is poorly understood due to lacking well-established and well-accepted visible models in vitro and in vivo. Here, consistent with one recent report, we found Mycobacterium marinum (M. marinum) invade the zebrafish brain and subsequently cause granuloma-like structures. We further showed that M. marinum, which shares similar characteristics with M. tuberculosis, can invade microglia and replicate in microglia, which subsequently promote the secretion of pro-inflammatory cytokines such as IL-1ß, IL-6, and TNF-α. M. marinum infection in microglia can also promote autophagy, which conversely limits the replication of M. marinum. Thus, pharmacological activation of autophagy by rapamycin could prevent M. marinum replication. Our study provides in vivo and in vitro models to study underlying pathogenic mechanisms of tubercular meningitis by using M. marinum. Our results also showed that activation of autophagy could be a meaningful way to prevent tubercular meningitis.

Polarization-dependent strong coupling between surface plasmon polaritons and excitons in an organic-dye-doped nanostructure.

In this work, we demonstrate polarization-dependent strong coupling between surface plasmon polaritons (SPPs) and excitons in the J-aggregates-attached aperture array. It is shown that the excitons strongly couple with the polarization-dependent SPPs, and Rabi splittings are consequently observed. As a result, the polarization-dependent polariton bands are generated in the system. Increasing the incident angle, the polaritons disperse to higher energies under transverse-electric illumination, while the polaritons disperse to lower energies under transverse-magnetic illumination. Therefore, at different polarization incidence, we experimentally achieve distinct polaritons with opposite dispersion directions. In this way, tuning the polarization of the incident light, we can excite different polaritons whose energy propagates to different directions. Furthermore, by retrieving the mixing fractions of the components in these polariton bands, we find that the dispersion properties of the polaritons are inherited from both the SPPs and the excitons. Our investigation may inspire related studies on tunable photon-exciton interactions and achieve some potential applications on active polariton devices.

Miniature spectrometer based on diffraction in a dispersive hole array.

We present an ultra-compact spectrometer that uses a 10×10 hole array as the dispersive component. Our analysis shows that the two-dimensional intensity distribution can be modeled by a system of simultaneous linear equations when the size of each hole in the dispersive component has been pre-designed appropriately. One can readily recover the spectral contents of the input radiation by solving the linear equation system with regularized procedure. Experimental results show that the reconstruction range is at least within the entire visible band, which can be further extended if a near-infrared CCD is used. One therefore envisions strong potential for many wavelength analysis applications.

Ultra-broadband and strongly enhanced diffraction with metasurfaces.

Enhanced high-order diffractions which are spatially dispersive are desirable in such as spectroscopy studies, thin-film solar cells, etc. Conventionally, the dielectric gratings can be used to realize the enhanced diffraction, but the facets are usually rugged and optically thick (~µm). Plasmonic materials may exhibit unprecedented ability for manipulating light. Nonetheless, much interest has been focused on the subwavelength metasurfaces working in the zero-order regime. Here, we show that ultra-broadband and strongly enhanced diffraction can be achieved with the super-wavelength metasurfaces. For the purpose, we employ symmetric or asymmetric metal patches on a ground metal plane, which support the localized oscillation of free electrons and enhanced scattering of light. The zero-order reflection is suppressed, giving rise to an enhancement of first-order diffraction (50 ~ 95%) in an ultra-wide bandwidth (600 ~ 1500 nm). The proposed plasmonic structure is planar and ultra-thin (with an etching depth of only 80 nm), showing new potential for constructing compact and efficient dispersive elements.

Position-sensitive spectral splitting with a plasmonic nanowire on silicon chip.

On-chip nanophotonics serves as the foundation for the new generation of information technology, but it is challenged by the diffraction limit of light. With the capabilities of confining light into (deep) subwavelength volumes, plasmonics makes it possible to dramatically miniaturize optical devices so as to integrate them into silicon chips. Here we demonstrate that by cascading nano-corrugation gratings with different periodicities on silver nanowires atop silicon, different colors can be spatially separated and chronologically released at different grating junctions. The released light frequency depends on the grating arrangement and corrugation periodicities. Hence the nanowire acts as a spectral splitter for sorting/demultiplexing photons at different nano-scale positions with a ten-femtosecond-level interval. Such nanowires can be constructed further into compact 2D networks or circuits. We believe that this study provides a new and promising approach for realizing spatiotemporal-sensitive spectral splitting and optical signal processing on nanoscales, and for general integration of nanophotonics with microelectronics.

An investigation of the effects of self-assembled monolayers on protein crystallisation.

Most protein crystallisation begins from heterogeneous nucleation; in practice, crystallisation typically occurs in the presence of a solid surface in the solution. The solid surface provides a nucleation site such that the energy barrier for nucleation is lower on the surface than in the bulk solution. Different types of solid surfaces exhibit different surface energies, and the nucleation barriers depend on the characteristics of the solid surfaces. Therefore, treatment of the solid surface may alter the surface properties to increase the chance to obtain protein crystals. In this paper, we propose a method to modify the glass cover slip using a self-assembled monolayer (SAM) of functional groups (methyl, sulfydryl and amino), and we investigated the effect of each SAM on protein crystallisation. The results indicated that both crystallisation success rate in a reproducibility study, and crystallisation hits in a crystallisation screening study, were increased using the SAMs, among which, the methyl-modified SAM demonstrated the most significant improvement. These results illustrated that directly modifying the crystallisation plates or glass cover slips to create surfaces that favour heterogeneous nucleation can be potentially useful in practical protein crystallisation, and the utilisation of a SAM containing a functional group can be considered a promising technique for the treatment of the surfaces that will directly contact the crystallisation solution.

Optical properties of a planar metamaterial with chiral symmetry breaking.

The optical properties of a planar metamaterial with gammadion-shaped chiral symmetry breaking holes array have been investigated both theoretically and experimentally. The results indicate that the introduction of the chiral symmetry breaking causes the split of the transmission peak and exerts large influence on the optical rotation and circular dichroism. Our metamaterials might have potential applications in future design of plasmonic devices.

Fanolike resonance due to plasmon excitation in linear chains of metal bumps.

We report the transmission anomaly in a modified slit grating, which is dressed, on the slit sidewalls, with the linear chains of metal bumps. An asymmetric lineshape, which is characteristic of the Fano resonance, has been found in a narrow frequency range of the spectrum. The effect can be attributed to the interference between nonresonant background transmission and resonant plasmonic wave excitation in the linear chains. The dispersion of chain plasmon mode has been suggested, enabling the dynamic tuning of spectral position of the Fano effect.

Optical properties of a metal film perforated with coaxial elliptical hole arrays.

The optical properties of a metal film perforated with coaxial elliptical hole arrays have been investigated experimentally and a simple analysis model that qualitatively explains the experimental results has been presented. In our structure, two localized excitations, i.e., the short- and long-axis localized surface-plasmon modes of the elliptical nanoparticles or nanoholes can be excited, which couples, respectively, with the surface-plasmon polariton modes and causes different optical response. As a consequence, the transmission features can be manipulated by the polarization state of the incident light.

Microfiber-probe-based ultrasmall interferometric sensor.

We report an ultrasmall microfiber-probe-based reflective interferometer for highly sensitive liquid refractive index measurement. It has a 3.5 microm micronotch cavity fabricated by focused ion beam micromachining. A sensitivity of 110 nm/RIU (refractive index unit) in liquid is achieved with over 20 dB extinction ratio. Theoretical analysis shows this kind of device is a hybrid of Fabry-Perot and modal interferometers. In comparison with normal fiber interferometers, this probe sensor is very compact, stable, and cheap, offering great potentials for detecting inside sub-wavelength bubbles, droplets, or biocells.

Long-wavelength optical properties of a plasmonic crystal.

The optical properties of a plasmonic crystal composed of gold nanorod particles have been studied. Because of the strong coupling between the incident light and vibrations of free electrons, the long-wavelength optical properties such as the dielectric abnormality and polariton excitation etc., which were suggested originally in ionic crystals, can also be present in the plasmonic crystal. The results show that the plasmonic and ionic lattices may share a common physics.

Nanoscale optical field localization by resonantly focused plasmons.

We experimentally demonstrate use of plasmonic resonant phenomena combined with strong field localization to enhance efficiency of confining optical fields in a Si waveguide. Our approach utilizes a plasmonic resonant nano-focusing-antenna (RNFA), that simultaneously supports several focusing mechanisms in a single nanostructure, integrated with a lossless Si waveguide utilized with silicon-on-insulator (SOI) technology, to achieve a sub-diffraction limited focusing with a nanoscale (deeply subwavelength) spot size. The metallic RNFA effectively converts an incoming propagating waveguide mode to a localized resonant plasmon mode in an ultrasmall volume in all 3 dimensions. The near-field optical measurements of the fabricated RNFA using heterodyne near-field scanning optical microscope (H-NSOM) validate the theoretical predictions showing strong optical field localization.