Growth of giant two-dimensional crystal of protein molecules from a three-phase contact line

A novel method to fabricate a two-dimensional (2D) crystal of protein molecules has been developed. The method enables us to control both the position of nucleation and the direction of the crystal growth. The crystal obtained using a protein molecule, ferritin, was found to be composed of a number of densely packed single crystal domains with an unprecedentedly large size of approximately 100 microm(2). This method also reveals characteristic behavior of the spatiotemporal evolution of the crystal; for example, "fusion" of the crystal domains, which is never observed in an ordinary crystal composed of atoms or ions, was demonstrated. Our approach could have potential in fabricating extraordinarily large and highly ordered nanoparticle arrays of organic or inorganic materials.     

Characterizing the structural transition of cationic DPPC liposomes from the approach of TEM, SAXS and AFM measurements

The structural transition of L-alpha-dipalmitoylphosphatidylcholine (DPPC) liposomes, caused by the addition of a small amount of stearylamine (SA), has been characterized. It has been reported that the shape of DPPC liposomes changes from multilamellar vesicles to large-unilamellar vesicles at the molar concentration ratio of DPPC/SA=9.5/0.5, however, the possible diving factors for this phenomenon have not so far been presented. Flat lipid membranes consisting of DPPC and SA, prepared by the quasi-Bangham method or the Langmuir-Blodgett (LB) technique, are employed in this study when considering the molecular interaction in and between lipid membranes, which should play a key role for determining the liposome shape. The colloid probe atomic force microscopy reveals that the addition of SA results in an inter-film electrosteric repulsion. This repulsive interaction causes a significant increase in the inter-film distance, which is confirmed with freeze-fracture transmission electron microscopy (FF-TEM) and small-angle X-ray scattering (SAXS), and thereby, the large-unilamellar vesicles are formed for reducing the inter- and intra-firm repulsive forces. Taking the molecular structures into consideration, it seems that the shape transition of DPPC liposomes results from such electrostatic interactions as well as packing geometry of the two components.     

Evaluation of microwave-assisted extraction for the analysis of polychlorinated biphenyls and organochlorine pesticides in fish

The efficiency of microwave-assisted extraction (MAE) was evaluated for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish. An isotope dilution method was used for quantification via analysis of the samples by gas chromatography and mass spectrometry. MAE solvent, temperature, and time were optimized, and observed concentrations were compared. The MAE results were also compared to those of other extraction techniques (Soxhlet extraction, pressurized liquid extraction, saponification, and homogenization). Concentrations of PCBs and OCPs obtained by MAE at 120 degrees C for 10 min were comparable to those by the other techniques. The results suggest that MAE can be used for the analysis of PCBs and OCPs in fish.     

The Expanded Red/Green Cyanobacteriochrome Lineage: An Evolutionary Hot Spot

This article highlights the paper by Rockwell et al. in the current issue of Photochemistry and Photobiology. Rockwell et al. describe the discovery of novel two‐Cys photocycles within the “expanded red/green” (XRG) cyanobacteriochrome (CBCR) lineage. Comprehensive phylogenetic analysis revealed that several XRG CBCRs possess a second Cys residue in the DXCF (Asp‐Xaa‐Cys‐Phe) motif conserved among the DXCF CBCR lineage. Spectral studies identified that these CBCRs showed green/blue or ultraviolet/blue reversible photoconversion abilities. The green/blue reversible photocycle had not been reported previously among the XRG CBCR lineage. Based on these findings, Rockwell et al. replaced three amino acid residues in a red/green reversible CBCR, NpR6012g4, and succeeded in constructing a violet/green reversible photocycle. These findings, together with previous studies, provide a good explanation for the evolutionary flexibility of the XRG CBCRs.     

Elemental Analysis of Biodiesel by Inductively Coupled Plasma Optical Emission and Flame Atomic Absorption Spectrometries

The extraction of 21 elements from biodiesel using aqueous acid and alkaline solutions was investigated as pretreatment to permit their determination by inductively coupled plasma optical emission spectrometry and flame atomic absorption spectrometry. Al, Ca, Cd, Cu, K, Mg, Mn, Na, V, and Zn were completely extracted from the biodiesel fuel with aqueous acid solution, and Na was completely extracted with alkaline solution. Extraction characteristics varied from element to element; however, 100?±?5% recoveries were obtained with a 30-s extraction procedure. Therefore, although biodiesel is an organic lipophilic material, these elements were determined in aqueous solution. The extracted elements were determined based on traceable Japan calibration service system standards. Accurate analysis of biodiesel was performed using the reported protocol.     

CONTROLLED SYNTHESIS OF AMPHIPHILIC BLOCK POLYMERS HAVING GLUCOSE RESIDUES AND THEIR STRUCTURE FORMATION

Vinyl ether (VE)-based amphiphilic block copolymers with D-glucose residues as hydrophilicpendants were synthesized by CH_3 CH(OiBu)Cl/ZnI_2-initiated sequential living cationic copolymerization of3-O-(vinyloxy)ethyl-1, 2:5, 6-di-O-isopropylidene-D-glucofuranose (IGVE) and isobutyl VE (IBVE ) andsubsequent deprotection. The precursor block copolymers had a narrow molecular weight distribution(M_w/M_n～1.1) and a controlled segmental composition. The solubility characteristics of the amphiphiliccopolymer depended strongly on composition. Their solvent-cast thin films were examined, under atransmission electron microscope, and could be seen to exhibit various microphase-separated surfacemorphologies such as spheres, cylinders, and lamellae, depending on composition. The amphiphiliccopolymers with the appropriate segmental composition were found to form a stable monolayer at the air-water interface, which was successfully transferred onto a substrate by the Langmuir-Blodgett (LB)technique. The layered strucfure of the built-up LB films was controlled by blending the homopolymer.     

Average and extremal properties of heat transfer and shear stress on a wall surface in Rayleigh–Bénard convection

In this study surface-averaged and extremal properties of heat transfer and shear stress on the upper wall surface of Rayleigh–Bénard convection are numerically examined. The Prandtl number was raised up to 10³, and the Rayleigh number was changed between 10⁴ and 10⁷. As a result, average Nusselt number Nu and shear rate τ/Pr depends on Pr, Ra, and the entire numerical results are distributed between two correlation equations corresponding to small and large Pr. The small and large Pr equations are closely related to steady and unsteady flow regimes, respectively. Nevertheless, a single relation τ/Pr ~ Nu ^3.0 exists to explain the entire results. Similarly the change of local maximal properties Nu _max and τ _max/Pr depends on Pr, Ra, and these values are also distributed between two correlation equations corresponding to small and large Pr cases. Despite such complicated dependence we can obtain a correlation equation as a form of τ _max/Pr ~ Nu _max^2.6, which has not been obtained theoretically.     

Novel amphiphilic linear polymer/dendrimer block copolymer: Synthesis of poly(2-methyl-2-oxazoline)-block-poly(amido amine) dendrimer

Novel linear polymer/dendrimer block copolymers, poly(2-methyl-2-oxazoline)-block-poly(amido amine) dendrimers (water-soluble full-generation type 4 (G = 4.0 and 5.0) and amphiphilic half-generation type 5 (G = 3.5, 4.5, and 5.5)), were synthesized by divergent-growth dendrimer construction with ω-ethylenediamine-terminated poly(2-methyl-2-oxazoline), which was prepared by living ring-opening polymerization of 2-methyl-2-oxazoline. Assembly of the amphiphilic dendrimer-based block copolymer (G = 5.5) was investigated by surface tension measurements (critical micelle concentration, 0.49 wt.-%) and by small-angle neutron scattering analysis (spherical particles; assembled number, ca. 10³).