Polymerization of Acrylamide in Aqueous Solution of Poly(N‐isopropylacrylamide) at Lower Critical Solution Temperature

Acrylamide (AAm) was found to polymerize in a solution of poly(N‐isopropylacrylamide) (PNIPAAm) in water at around its lower critical solution temperature (LCST) (32°C) without any initiators. This phenomenon was specifically observed in aqueous solutions of the polymers having LCST such as PNIPAAm and poly(methylvinylether) (PMVE). AAm polymerized only when PNIPAAm and AAm were dissolved in water below LCST of PNIPAAm and then the solution was warmed up to the polymerization temperature (40°C). On the other hand, the polymerization of AAm did not proceed when AAm was added into aqueous PNIPAAm solution during and after the phase separation above 32°C. Furthermore the polymerizability of AAm was remarkably affected by the concentration and molecular weight of the PNIPAAm additives. Under the condition of lower PNIPAAm concentration (0.30 mol/L), the increase in the molecular weight of PNIPAAm considerably increased the molecular weight of the resulting PAAm but decreased the yield of PAAm. Under the condition of higher PNIPAAm concentration (0.60 mol/L) the polymerizability was not so affected by the molecular weight of PNIPAAm, while the molecular weight of PAAm formed by using higher molecular weight PNIPAAm was higher than those of PAAm formed by using lower molecular weight PNIPAAm. Moreover, the molecular weight of PAAm formed by the PNIPAAm induced polymerization of AAm was much higher than that of the polymer obtained by the radical polymerization using AIBN in THF or VA‐ 061 in water.     

Extended string field theory for massless higher-spin fields

We propose a new gauge field theory which is an extension of ordinary string field theory by assembling multiple state spaces of the bosonic string. The theory includes higher-spin fields in its massless spectrum together with the infinite tower of massive fields. From the theory, we can easily extract the minimal gauge-invariant quadratic action for tensor fields with any symmetry. As examples, we explicitly derive the gauge-invariant actions for some simple mixed symmetric tensor fields. We also construct covariantly gauge-fixed action by extending the method developed for string field theory.     

Magnetically and Near‐Infrared Light‐Powered Supramolecular Nanotransporters for the Remote Control of Enzymatic Reactions

Cancer is one of the primary causes of death worldwide. A high‐precision analysis of biomolecular behaviors in cancer cells at the single‐cell level and more effective cancer therapies are urgently required. Here, we describe the development of a magnetically‐ and near infrared light‐triggered optical control method, based on nanorobotics, for the analyses of cellular functions. A new type of nanotransporters, composed of magnetic iron nanoparticles, carbon nanohorns, and liposomes, was synthesized for the spatiotemporal control of cellular functions in cells and mice. Our technology will help to create a new state‐of‐the‐art tool for the comprehensive analysis of “real” biological molecular information at the single‐cell level, and it may also help in the development of innovative cancer therapies.     

Synthesis and crystal structures of CaY2Ge3O10 and CaY2Ge4O12

New compounds CaY₂Ge₃O₁₀ and CaY₂Ge₄O₁₂ were prepared by heating mixtures of CaCO₃, Y₂O₃ and GeO₂ at 1200 °C. CaY₂Ge₃O₁₀ is stable at 1300 °C, while CaY₂Ge₄O₁₂ decomposes into a melt and CaY₂Ge₃O₁₀ at approximately 1250 °C. We obtained single crystals of CaY₂Ge₃O₁₀ by cooling a sample with an initial composition of Ca:Y:Ge=1:2:8 from 1300 °C with a rate of −6 °C/h. The crystal structure of CaY₂Ge₃O₁₀ was determined by single crystal X-ray diffraction. CaY₂Ge₃O₁₀ crystallizes in the monoclinic space group P2₁/c with a=6.0906(8), b=6.8329(8), and β=109.140(3)°, Z=4, and R₁=0.029 for I>2σ(I). In the structure of CaY₂Ge₃O₁₀, Ca and Y atoms are situated disorderly in three 7-fold coordination sites between isolated germanate groups of triple GeO₄ tetrahedra, Ge₃O₁₀. The structural formula of CaY₂Ge₃O₁₀ is expressed as (Ca_0.45Y_0.55)(Ca_0.46Y_0.54)(Ca_0.09Y_0.91)Ge₃O₁₀. The crystal structure of CaY₂Ge₄O₁₂ was analyzed by the Rietveld method for the X-ray powder diffraction pattern. CaY₂Ge₄O₁₂ is isotypic with SrNa₂P₄O₁₂, crystallizing in the orthorhombic space group P4/nbm, a=9.99282(6), , Z=2, R_wp=0.092, R_p=0.067. CaY₂Ge₄O₁₂ contains four-membered GeO₄-tetrahedra rings, Ge₄O₁₂. Eight-fold coordinated square-anitiprism sites and 6-fold octahedral sites between the layers of the Ge₄O₁₂ rings are occupied by Y atom and Ca/Y atoms, respectively The structural formula is Y(Ca_0.5Y_0.5)₂Ge₄O₁₂.     

Total Synthesis of Proposed Structure of Yuremamine and All Diastereomers Using [3+2]‐Cycloaddition of Platinum‐Containing Azomethine Ylide

Total synthesis of the proposed structure of yuremamine has been achieved for the first time based on the intermolecular [3+2]‐cycloaddition reaction of the platinum‐containing azomethine ylide. All the possible diastereomers of yuremamine were also synthesized via the common intermediate. Through these syntheses, it was confirmed that the proposed structure of yuremamine and the diastereomers differ from the natural product.     

Dynamics of ice nucleation on water repellent surfaces

Prevention of ice accretion and adhesion on surfaces is relevant to many applications, leading to improved operation safety, increased energy efficiency, and cost reduction. Development of passive nonicing coatings is highly desirable, since current antiicing strategies are energy and cost intensive. Superhydrophobicity has been proposed as a lead passive nonicing strategy, yet the exact mechanism of delayed icing on these surfaces is not clearly understood. In this work, we present an in-depth analysis of ice formation dynamics upon water droplet impact on surfaces with different wettabilities. We experimentally demonstrate that ice nucleation under low-humidity conditions can be delayed through control of surface chemistry and texture. Combining infrared (IR) thermometry and high-speed photography, we observe that the reduction of water-surface contact area on superhydrophobic surfaces plays a dual role in delaying nucleation: first by reducing heat transfer and second by reducing the probability of heterogeneous nucleation at the water-substrate interface. This work also includes an analysis (based on classical nucleation theory) to estimate various homogeneous and heterogeneous nucleation rates in icing situations. The key finding is that ice nucleation delay on superhydrophobic surfaces is more prominent at moderate degrees of supercooling, while closer to the homogeneous nucleation temperature, bulk and air-water interface nucleation effects become equally important. The study presented here offers a comprehensive perspective on the efficacy of textured surfaces for nonicing applications.     

Intense Red-Blue Luminescence Based on Superfine Control of Metal–Metal Interactions for Self-Assembled Platinum(II) Complexes

A series of assembled Pt^II complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)₂(R-impy)] (R-impyH⁺=1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me ( Pt-Me ), Et ( Pt-Et ), ⁱPr ( Pt- ⁱ Pr ), and ^tBu ( Pt- ^t Bu )). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51–0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (³MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt- ^t Bu . Importantly, Pt- ^t Bu is the first example that exhibits blue ³MMLCT emission. The ³MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the ³MMLCT emission presents a new strategy of superfine control of the emission color.     

Experimental detection of proteolytic activity in a signal peptide peptidase of Arabidopsis thaliana

Background

The ubiquitin ligase COP1, COnstitutively Photomorphogenic 1, functions in many biological responses in mammalian cells, but its downstream pathway remains unclear.

Results

Here, we identified FIP200, a key regulator of mammalian autophagy, as a novel COP1-interacting protein by yeast two-hybrid screening. The interaction was confirmed by a GST-pulldown assay. Split-GFP analysis revealed that interaction between COP1 and FIP200 predominantly occurred in the cytoplasm and was enhanced in cells treated with UV irradiation. Different forms of FIP200 protein were expressed in cultured mammalian cells, and ectopic expression of COP1 reduced one of such forms.

Conclusions

These data suggest that COP1 modulates FIP200-associated activities, which may contribute to a variety of cellular functions that COP1 is involved in.     

Protective Effect of Ferulic Acid against Hydrogen Peroxide Induced Apoptosis in PC12 Cells

Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H₂O₂) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H₂O₂-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H₂O₂ through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H₂O₂-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H₂O₂ stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.