Dispersionless and Giant Optical Activity in Terahertz Chiral Metamaterials

In this paper, we propose a new structure which is achieved via the combination of twist conjugated gammadion and four-L resonators pairs. The proposed chiral metamaterial can achieve dispersionless and giant optical activity simultaneously. The polarization ellipticity is lower than 0.46° through all function bands, and the polarization azimuth rotation angle is larger than 90.3° from 2.37 to 2.69 THz. Specifically, the structure can achieve 90° dispersionless polarization rotation at f?=?2.57 THz. The optical activity is optimized through changing the parameters of the chiral structure and the physical mechanism is also analyzed based on surface current distribution.     

Synthesis of Chiral NADH Model Compounds Containing a Sulfur Atom and Their Asymmetric Reduction

Oryzalexins A, B and C were isolated as a group of novel phytoalexins from rice (Oryza sativa) blast leaves infected with Pyricularia oryzae. The basis of the structures of Oryzalexins A, B and C was laid by spectroscopic methods and their inhibitory activities against spore germination and germ tube growth of P. oryzae were assayed.

Oryzalexins A, B and C, isolated from rice leaves infected with P. oryzae as a group of novel phytoalexins, were confirmed to be (+)-sandaracopimaradiene derivatives by chemical and spectroscopic studies, i.e. A: 3-oxy-7-oxo- (I); B: 3-oxo-7-oxy- (II) and C: 3,7-dioxo-(+)-sandaracopimaradiene (III).     

Stabilization of Precursor Solution and Perovskite Layer by Addition of Sulfur

Efficient perovskite solar cells (PSCs) are mainly fabricated by a solution coating processes. However, the efficiency of such devices varies significantly with the aging time of the precursor solution used to fabricate them, which includes a mixture of perovskite components, especially methylammonium (MA), and formamidinium (FA) cations. Herein, how the inorganic–organic hybrid perovskite precursor solution of (FAPbI₃)_0.95(MAPbBr₃)_0.05 degrades over time and how such degradation can be effectively inhibited is reported on, and the associated mechanism of degradation is discussed. Such degradation of the precursor solution is closely related to the loss of MA cations dissolved in the FA solution through the deprotonation of MA to volatile methylamine (CH₃NH₂). Addition of elemental sulfur (S₈) drastically stabilizes the precursor solution owing to amine–sulfur coordination, without compromising the power conversion efficiency (PCE) of the derived PSCs. Furthermore, sulfur introduced to stabilize the precursor solution results in improved PSC stability.     

Optical Activity Governed by Local Chiral Structures in Two‐Dimensional Curved Metallic Nanostructures

Chiral nanostructures show macroscopic optical activity. Local optical activity and its handedness are not uniform in the nanostructure, and are spatially distributed depending on the shape of the nanostructure. In this study we fabricated curved chain nanostructures made of gold by connecting linearly two or more arc structures in a two‐dimensional plane. Spatial features of local optical activity in the chain structures were evaluated with near‐field circular dichroism (CD) imaging, and analyzed with the aid of classical electromagnetic simulation. The electromagnetic simulation predicted that local optical activity appears at inflection points where arc structures are connected. The handedness of the local optical activity was dependent on the handedness of the local chirality at the inflection point. Chiral chain structures have odd inflection points and the local optical activity distributed symmetrically with respect to structural centers. In contrast, achiral chain structures have even inflection points and showed antisymmetric distribution. In the near‐field CD images of fabricated chain nanostructures, the symmetric and antisymmetric distributions of local CD were observed for chiral and achiral chain structures, respectively, consistent with the simulated results. The handedness of the local optical activity was found to be determined by the handedness of the inflection point, for the fabricated chain structures having two or more inflection points. The local optical activity was thus governed primarily by the local chirality of the inflection points for the gold chain structures. The total effect of all the inflection points in the chain structure is considered to be a predominant factor that determines the macroscopic optical activity. Chirality 28:540–544, 2016. © 2016 Wiley Periodicals, Inc.     

Remote Excited Raman Optical Activity of Adenine Along Ag Plasmonic Waveguide

We report the remote excited Raman optical activity (ROA) of adenine along Ag plasmonic waveguide. First, the surface plasmons that propagate along Ag nanowire is demonstrated experimentally. Second, the Raman spectra of adenine are measured experimentally. Third, the remote exited ROA by plasmonic waveguide are measured and compared. It is found that the plasmon chirality strongly influenced the molecular ORA by the local surface plasmon and remote plasmon waveguide. The plasmon chirality of nanostructures and the chirality plasmon waveguide should be considered in the experiments for the local and remote measurement.     

Intense Chiral Optical Phenomena in Racemic Polymers by Cocrystallization With Chiral Guest Molecules: A Brief Overview

This review is devoted to the chiral optical behavior of films of racemic polymers whose chirality is induced by cocrystallization with nonracemic (also temporary) guest molecules. We provide examples of macromolecular amplification of chirality, produced by molecular and supramolecular mechanisms, on industrially relevant polymers like poly(2,6‐dimethyl‐1,4‐phenylene)oxide (PPO) and syndiotactic polystyrene (s‐PS). Chirality 28:29–38, 2016. © 2015 Wiley Periodicals, Inc.     

Promotion of Cocklebur Seed Germination by Allyl, Sulfur and Cyanogenic Compounds

The effects of allyl, sulfur and cyanogenic compounds on thegermination of upper cocklebur (Xanthium pennsylvanicum Wallr.)seeds were examined. Mercaptoethanol and methylmercaptan aswell as KCN, substrates for rßcyanoalanine synthase(CAS), and H₂S and thiocyanate, the products of the CAS catalyzingreaction, were effective in promoting germination, suggestingthe involvement of CAS in germination. Most of allyl compounds, especially allylthiourea, as well asethylene which activated CAS [Hasegawa et al. (1994) Physiol.Plant. 91: 141], promoted the germination in an abnormal typewhich occurred by the predominant growth of cotyledons as didC₂H₄ [Katoh and Esashi (1975) Plant Cell Physiol. 16: 687].However, they failed to activate CAS unlike ethylene, and toliberate free ethylene during an incubation period. It was thuspossible that an C₂H₄-like double bond within allyl compoundscan act to promote seed germination. (Received June 10, 1996; Accepted August 21, 1996)     

Thermothrix thiopara: Growth and Metabolism of a Newly Isolated Thermophile Capable of Oxidizing Sulfur and Sulfur Compounds

Thermothrix thiopara is isolated from hot sulfur springs. It occurs in situ at a temperature of 72°C, a pH of 7.0, and an HS^- concentration of 17.4 μmol/liter (0.8 ppm). The organism was capable of autotrophic growth. Sulfite, sulfur, and polythionates were formed and subsequently degraded to sulfate during growth with thiosulfate as the sole energy source. Thiosulfate was oxidized by the polythionate pathway, and the stoichiometry of growth on thiosulfate was determined. The organism was also capable of heterotrophic growth in amino acids and simple sugars. A source of reduced sulfur (methionine, glutathione) was required for heterotrophic growth. Growth occurred aerobically or anaerobically with nitrate as a terminal oxidant. Both nitrous oxide and dinitrogen were produced. At 73°C the maximum autotrophic growth rate in batch culture using thiosulfate was 0.56 generation per h. Under the same conditions in continuous culture, washout occurred at a dilution rate of 0.3 to 0.4 per h, corresponding to a cellular growth rate of 0.43 to 0.58 generation per h. This was nearly three times the growth rate for Thiobacillus denitrificans. T. thiopara is gram negative. It was also found to be both lysozyme and penicillin susceptible. As a result, this organism cannot be considered an archaebacterium.     

Plasmonic Interaction Between Silver Nano-Cubes and a Silver Ground Plane Studied by Surface-Enhanced Raman Scattering

The plasmonic interaction between silver nano-cubes and a silver ground plane with and without a dielectric spacer is studied for surface-enhanced Raman scattering (SERS) for rhodamine 6G (R6G) molecules absorbed onto the silver nano-cubes. Experimental results show that the composite substrates made from silver nano-cubes and the silver ground plane produce a stronger SERS signal than by the cubes alone, due to the plasmonic interaction between the cubes and the film. Numerical simulation is used to verify the plasmonic enhancement of the composite substrate and is consistent with the experimental results. The lowest concentration of R6G molecules which can be detected with the composite substrate is about 10⁻¹¹ M with our setup.     

Modulation of DMT1 Activity by Redox Compounds

Iron(II) exacerbates the effects of oxidative stress via the Fenton reaction. A number of human diseases are associated with iron accumulation including ischemia-reperfusion injury, inflammation and certain neurodegenerative diseases. The functional properties and localization in plasma membrane of cells and endosomes suggest an important role for the divalent metal transporter DMT1 (also known as DCT1 and Nramp2) in iron transport and cellular iron homeostasis. Although iron metabolism is strictly controlled and the activity of DMT1 is central in controlling iron homeostasis, no regulatory mechanisms for DMT1 have been so far identified. Our studies show that the activity of DMT1 is modulated by compounds that affect its redox status. We also show that both iron and zinc are transported by DMT1 when expressed in Xenopus laevis oocytes. Radiotracer uptake and electrophysiological measurements revealed that H₂O₂ and Hg²⁺ treatments result in substantial inhibition of DMT1. These findings may have a profound relevance from a physiological and pathophysiological standpoint. Present address for D.T.: Department of Neurology, Cecil B. Day Laboratory for Neuromuscular Research, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA     

Carbon Conversion Efficiency and Limits of Productive Bacterial Degradation of Methyl tert-Butyl Ether and Related Compounds

The utilization of the fuel oxygenate methyl tert-butyl ether (MTBE) and related compounds by microorganisms was investigated in a mainly theoretical study based on the Y_ATP concept. Experiments were conducted to derive realistic maintenance coefficients and K_s values needed to calculate substrate fluxes available for biomass production. Aerobic substrate conversion and biomass synthesis were calculated for different putative pathways. The results suggest that MTBE is an effective heterotrophic substrate that can sustain growth yields of up to 0.87 g g⁻¹, which contradicts previous calculation results (N. Fortin et al., Environ. Microbiol. 3:407-416, 2001). Sufficient energy equivalents were generated in several of the potential assimilatory routes to incorporate carbon into biomass without the necessity to dissimilate additional substrate, efficient energy transduction provided. However, when a growth-related kinetic model was included, the limits of productive degradation became obvious. Depending on the maintenance coefficient m_s and its associated biomass decay term b, growth-associated carbon conversion became strongly dependent on substrate fluxes. Due to slow degradation kinetics, the calculations predicted relatively high threshold concentrations, S_min, below which growth would not further be supported. S_min strongly depended on the maximum growth rate μ_max, and b and was directly correlated with the half maximum rate-associated substrate concentration K_s, meaning that any effect impacting this parameter would also change S_min. The primary metabolic step, catalyzing the cleavage of the ether bond in MTBE, is likely to control the substrate flux in various strains. In addition, deficits in oxygen as an external factor and in reduction equivalents as a cellular variable in this reaction should further increase K_s and S_min for MTBE.     

Live Cell Response to Mechanical Stimulation Studied by Integrated Optical and Atomic Force Microscopy

To understand the mechanism by which living cells sense mechanical forces, and how they respond and adapt to their environment, a new technology able to investigate cells behavior at sub-cellular level with high spatial and temporal resolution was developed. Thus, an atomic force microscope (AFM) was integrated with total internal reflection fluorescence (TIRF) microscopy and fast-spinning disk (FSD) confocal microscopy. The integrated system is broadly applicable across a wide range of molecular dynamic studies in any adherent live cells, allowing direct optical imaging of cell responses to mechanical stimulation in real-time. Significant rearrangement of the actin filaments and focal adhesions was shown due to local mechanical stimulation at the apical cell surface that induced changes into the cellular structure throughout the cell body. These innovative techniques will provide new information for understanding live cell restructuring and dynamics in response to mechanical force. A detailed protocol and a representative data set that show live cell response to mechanical stimulation are presented.Download video file.^{(57M, mov)}     

Removal of Sulfur Compounds from Coal by the Thermophilic Organism Sulfolobus acidocaldarius

The thermophilic, reduced-sulfur, iron-oxidizing bacterium Sulfolobus acidocaldarius was used for the removal of sulfur compounds from coal. The inclusion of complex nutrients such as yeast extract and peptone, and chemical oxidizing agents, 0.01 M FeCl₃ into leaching medium, reduced the rate and the extent of sulfur removal from coal. The rate of sulfur removal by S. acidocaldarius was strongly dependent on the sulfur content of the coal and on the total external surface area of coal particles. Approximately 96% of inorganic sulfur was removed from a 5% slurry of coal which had an initial total sulfur content of 4% and an inorganic (pyritic S and sulfate) sulfur content of 2.1%. This resulted in removal of 50% of initial total sulfur present in coal.     

Plant-Derived Enzymes Producing Chiral Aroma Compounds and Potential Application

Aroma (volatile) compounds play important ecological functions in plants, and also contribute to the quality of plant-derived foods. Moreover, chiral aroma compounds affect their functions in plants and lead to different flavor quality properties. Formations of chiral aroma compounds are due to the presence of enzymes producing these compounds in plants, which are generally involved in the final biosynthetic step of the aroma compounds. Here, we review recent progress in research on the plant-derived enzymes producing chiral aroma compounds, and their changes in response to environmental factors. The chiral aroma enzymes that have been reported produce (R)-linalool, (S)-linalool, (R)-limonene, and (S)-limonene, etc., and these enzymes are found in various plant species. We also discuss the origins of enantioselectivity in the plant-derived enzymes producing chiral aroma compounds and summarize the potential use of plants containing enzymes producing chiral aroma compounds for producing chiral flavors/fragrances.     

Phototrophic Community in Gypsum Crust from the Atacama Desert Studied by Raman Spectroscopy and Microscopic Imaging

The hyperarid core of the Atacama Desert represents one of the driest places on Earth with an exceptional occurrence of microbial life coping with extreme environmental stress factors. The gypsum crusts have already been found to harbor diverse communities in this area. Here, we present a Raman spectroscopic study, complemented by correlative microscopic imaging using SEM-BSE and fluorescence microscopy, of the endolithic microbial communities inside the Ca-sulphate crusts dominated by phototrophic microorganisms. Differences of pigment composition within different zones follow the cyanobacterial and algal colonization and also reveal the degradation of phycobiliproteins within the decayed biomass of cyanobacteria. Carotenoids of at least three different types were recognized, differing in dependence on the particular phylum of phototrophic microorganisms. Moreover, calcium oxalate monohydrate – whewellite – was found to be associated with the algae and hyphal associations living in the lower regions of the crust. The 785 nm excitation wavelength employed here was found to be the correct source for studying pigment composition as well as for the detection of the oxalate. A comparison of these results with those using 514.5 nm laser excitation which is widely adopted for the detection of carotenoids due to the resonance Raman effect is made and discussed.     

Maltodextrins as Chiral Selectors in CE: Molecular Structure Effect of Basic Chiral Compounds on the Enantioseparation

Prediction of chiral separation for a compound using a chiral selector is an interesting and debatable work. For this purpose, in this study 23 chiral basic drugs with different chemical structures were selected as model solutes and the influence of their chemical structures on the enantioseparation in the presence of maltodextrin (MD) as chiral selector was investigated. For chiral separation, a 100‐mM phosphate buffer solution (pH 3.0) containing 10% (w/v) MD with dextrose equivalent (DE) of 4‐7 as chiral selector at the temperature of 25°C and voltage of 20 kV was used. Under this condition, baseline separation was achieved for nine chiral compounds and partial separation was obtained for another six chiral compounds while no enantioseparation was obtained for the remaining eight compounds. The results showed that the existence of at least two aromatic rings or cycloalkanes and an oxygen or nitrogen atom or –CN group directly bonded to the chiral center are necessary for baseline separation. With the obtained results in this study, chiral separation of a chiral compound can be estimated with MD‐modified capillary electrophoresis before analysis. This prediction will minimize the number of preliminary experiments required to resolve enantiomers and will save time and cost. Chirality 26:620–628, 2014. © 2014 Wiley Periodicals, Inc.     

氰类和酯类取代基水溶金属卟啉与DNA相互作用的共振拉曼研究

用共振拉曼和紫外－可见吸收光谱研究了水溶金属卟啉４－Ｎ－乙酸乙酯基－吡啶基铜卟啉和镍卟啉［简称Ｃｕ（ＮＥＡＥ）和Ｎｉ（ＮＥＡＥ）］及４－Ｎ－乙腈基－吡啶基铜卟啉［简称Ｃｕ（ＮＡＣＮ）］与小牛胸腺ＤＮＡ的相互作用。分析表明Ｃｕ（ＮＥＡＥ）、Ｎｉ（ＮＥＡＥ）和Ｃｕ（ＮＡＣＮ）分别以外部键联、部分插入和沟槽方式与ＤＮＡ作用;卟啉插入ＤＮＡ时吡啶基团向卟啉环平面转动但不可能转成与之共面;而以非插入方式作用时吡啶基团会向垂直于或者平行于卟啉环平面转动。吡啶取代基的大小和空间位阻是影响相互作用方式的关键因素之一。