Symmetry selective third harmonic generation from plasmonic metacrystals

Nonlinear processes are often governed by selection rules imposed by the symmetries of the molecular configurations. The most well-known examples include the role of mirror symmetry breaking for the generation of even harmonics, and the selection rule related to the rotation symmetry in harmonic generation for fundamental beams with circular polarizations. While the role of mirror symmetry breaking in second harmonic generation has been extensively studied in plasmonic systems, the investigation on selection rules pertaining to circular polarization states of harmonic generation has been limited to crystals, i.e. symmetries at the atomic level. Here we demonstrate the rotational symmetry dependent third harmonic generation from nonlinear plasmonic metacrystals. We show that the selection rule can be imposed by the rotational symmetry of meta-crystals embedded into an isotropic organic nonlinear thin film. The results presented here may open new avenues for designing symmetry-dependent nonlinear optical responses with tailored plasmonic nanostructures.Comment: 13 pages, 3 figure

Giant nonlinear optical activity of achiral origin in planar metasurfaces with quadratic and cubic nonlinearities

3D chirality is shown to be unnecessary for introducing strong circular dichroism for harmonic generations. Specifically, near-unity circular dichroism for both second-harmonic generation and third-harmonic generations is demonstrated on suitably designed ultrathin plasmonic metasurfaces with only 2D planar chirality. The study opens up new routes for designing chip-type biosensing platform, which may allow for highly sensitive detection of bio- and chemical molecules with weak chirality

The effects of a synthetic curcuminoid analogue,2,6-bis-(4-hydroxyl-3-methoxybenzylidine)cyclohexanone on proinflammatorysignaling pathways and CLP-induced lethal sepsis in mice.

We previously showed that 2,6-bis-(4-hydroxyl-3-methoxybenzylidine)cyclohexanone (BHMC), suppressed the synthesis of various proinflammatory mediators. In this study we explain the mechanism of action of BHMC in lipopolysaccharide (LPS)-induced U937 monocytes and further show that BHMC prevents lethality of CLP-induced sepsis. BHMC showed dose-dependent inhibitory effects on p38, JNK and ERK 1/2 activity as determined by inhibition of phosphorylation of downstream transcription factors ATF-2, c-Jun and Elk-1 respectively. Inhibition of these transcription factors subsequently caused total abolishment of AP-1–DNA binding. BHMC inhibited p65 NF-κB nuclear translocation and DNA binding of p65 NF-κB only at the highest concentration used (12.5 μM) but failed to alter phosphorylation of JNK, ERK1/2 and STAT-1. Since the inhibition of p38 activity was more pronounced we evaluated the possibility that BHMC may bind to p38. Molecular docking experiments confirmed that BHMC fits well in the highly conserved hydrophobic pocket of p38 MAP kinase. We also show that BHMC was able to improve survival from lethal sepsis in a murine caecal-ligation and puncture (CLP) model

Effects of 3-(2-Hydroxyphenyl)-1-(5-methyl-furan-2-y-l) propenone (HMP) upon signalling pathways of lipopolysaccharide-induced iNOS synthesis in RAW 264.7 cells.

NO synthesis in the RAW 264.7 murine macrophage line. The inhibition of NO synthesis was related to inhibition of p38 phosphorylation and kinase activity that led to significant inhibition of phosphorylation of ATF-2. This effect in turn caused inhibition of AP-1-DNA binding which partially explains the inhibitory effect upon the synthesis of iNOS. HMP had no effect upon phosphorylation of JNK, ERK1/2 and STAT-1. Kinase activity of JNK and ERK1/2 was also not affected by HMP as determined by levels of phosphorylated c-jun and phosphorylated elk-1. Furthermore HMP failed to block phosphorylation of IκBα, and subsequent nuclear translocation and DNA-binding activity of p65 NF-κB in IFN-γ/LPS-induced RAW 264.7 cells. Molecular docking experiments confirmed that HMP fits well in the highly conserved hydrophobic pocket of p38 MAP kinase. We conclude that the synthetic HMP is a chalcone analogue that selectively inhibits the p38/ATF-2 and AP-1 signaling pathways in the NO synthesis by the macrophage RAW 264.7

A synthetic curcuminoid derivative inhibits nitric oxide and proinflammatory cytokine synthesis

Curcumin is a highly pleiotropic molecule with significant regulatory effects upon inflammation and inflammatory related diseases. However curcumin has one major important limitation in which it has poor bioavailability. Design of synthetic structural derivatives of curcumin is but one approach that has been used to overcome its poor bioavailability while retaining, or further enhancing, its drug-like effects. We have synthesized a series of curcumin analogues and describe the effects of 2,6-bis-4-(hydroxyl-3-methoxy-benzylidine)-cyclohexanone or BHMC upon nitric oxide and cytokine synthesis in cellular models of inflammation. BHMC showed a significant dose-response inhibitory action upon the synthesis of NO and we have shown that this effect was due to suppression of both iNOS gene and enzyme expression without any effects upon scavenging of nitrite. We also demonstrated that BHMC has a very minimal effect upon iNOS activity with no effect at all upon the secretion of PGE(2) but has a strong inhibitory effect upon MCP-1 and IL-10 secretion and gene expression. Secretion and gene expression of TNF-alpha and IL-6 were moderately inhibited whereas IL-8 and IL-1beta were not altered. We conclude that BHMC selectively inhibits the synthesis of several inflammatory mediators. BHMC should be considered a promising drug lead for preclinical and further pharmacological studies

Role of deep eutectic solvents as pretreatment medium for biomass transformation

Traditionally, biomass utilization was realized through the concept of biorefineries and the purpose of using biomass was mostly energy-driven. Over the years, the concept of biomass valorization shifted its focus toward unleashing the maximum potential of biomass in downstream processing such as for the production of various energy carriers and value-added bioproducts or chemicals. The main stepping stone toward realizing biomass transformation can be attributed to the ubiquitous nature of biomass, from which most of the biopolymers exhibited high recalcitrance in common solvents due to the heterogeneous polyphenolic structure of the lignin and the highly ordered cellulose’s crystalline structure. The recalcitrance of biomass poses constraints in the biomass-to-biofuels conversion or other valueadded bioproducts which typically involves three major steps: pretreatment, hydrolysis, and fermentation (Binod & Pandey, 2015). The pretreatment of biomass can be regarded as the most important step in biomass processing. In this sense, the goal of biomass pretreatment is to disintegrate the lignin barrier and make the celluloses, hemicelluloses, and other substrates accessible, as well as to enable the further processing and recovery of the valuable components embedded within the biomass

Role of deep eutectic solvents as pretreatment medium for biomass transformation

Traditionally, biomass utilization was realized through the concept of biorefineries and the purpose of using biomass was mostly energy-driven. Over the years, the concept of biomass valorization shifted its focus toward unleashing the maximum potential of biomass in downstream processing such as for the production of various energy carriers and value-added bioproducts or chemicals. The main stepping stone toward realizing biomass transformation can be attributed to the ubiquitous nature of biomass, from which most of the biopolymers exhibited high recalcitrance in common solvents due to the heterogeneous polyphenolic structure of the lignin and the highly ordered cellulose’s crystalline structure. The recalcitrance of biomass poses constraints in the biomass-to-biofuels conversion or other valueadded bioproducts which typically involves three major steps: pretreatment, hydrolysis, and fermentation (Binod & Pandey, 2015). The pretreatment of biomass can be regarded as the most important step in biomass processing. In this sense, the goal of biomass pretreatment is to disintegrate the lignin barrier and make the celluloses, hemicelluloses, and other substrates accessible, as well as to enable the further processing and recovery of the valuable components embedded within the biomass