New exo/endo selectivity observed in monohydrolysis of dialkyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates

New monohydrolysis reactions of several exo or endo dimethyl or diethyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates showed higher selectivity toward monohydrolyses of exo-carboalkoxy groups, although the reaction centers are located away from the norbornene rings.     

Performance Check of Vegetation Fluorescence Imaging Lidar through In Vivo and Remote Estimation of Chlorophyll Concentration Inside Plant Leaves

Laser-induced fluorescence imaging lidar was developed for in vivo plant/vegetation monitoring. Fluorescences of poplar tree leaves growing naturally at a distance of 60 m from the lidar were successfully detected as two spectral images at wavelengths of 685 nm and 740 nm. By comparing chlorophyll concentration quantified with high performance liquid chromatography, it was confirmed that the intensity ratio of the two wavelengths was converted into the chlorophyll concentration inside the leaves. The intensity ratio of the images reflected the status of the poplar tree in the process of senescence so well that it was possible to assess the living status of the tree as a numerical value. The performance characteristics and the potential of the laser-induced fluorescence imaging lidar for monitoring the physiological activities of plants and vegetation are described.     

First asymmetric enantioselective total synthesis of phenanthridine alkaloid, (S)-(+)-asiaticumine and its enantiomer

In this study, the first asymmetric enantioselective total syntheses of (+)-asiaticumine A (2) and its enantiomer were accomplished through a seven-step sequence using the bond formation between the C4a and N5 positions of the phenanthridine framework based on the microwave-assisted electrocyclization of cyclohexenylbenzaldoxime methyl ether as an aza 6π-hexatriene system followed by the Sharpless asymmetric dihydroxylation as the key step. In addition, the absolute configuration of natural (+)-2 was determined to be S by Mosher’s method.     

Folding thermodynamics of PET-hydrolyzing enzyme Cut190 depending on Ca2+ concentration

The enzyme, cutinase from Saccharomonospora viridis AHK190 (Cut190), can hydrolyze the inner block of polyethylene terephthalate (PET). Cut190 has a unique feature that both its activity and thermal stability are increased upon Ca²⁺ binding. In consideration of the glass transition temperature of PET, which is between 60 and 65 °C, the increased activity and thermal stability are of great interest to apply for PET bio-recycling. Our previous mutational analysis showed that the S226P/R228S mutant (Cut190*) has a higher activity and thermal stability than those of the wild type. In this study, we analyzed the folding thermodynamics of the inactive mutant of Cut190*, Cut190*S176A, using circular dichroism and differential scanning calorimetry. The results show that the denaturation temperature increases from 54 to 71 °C due to the addition of 250 mM Ca²⁺, in a Ca²⁺ concentration-dependent manner. The increased thermal stability is mainly due to the increased enthalpy change, partially compensated by the increased entropy change. Based on the crystal structure of Cut190*S176A bound to Ca²⁺, molecular dynamics simulations were carried out to analyze the effects of Ca²⁺ on the structural dynamics, showing that the Ca²⁺-bound structure fluctuated less than the Ca²⁺-free structure. Structural analysis indicates that Ca²⁺ binding increases the intramolecular interactions of the enzyme, while decreasing its fluctuation, which are in good correlation with the experimental results of the folding thermodynamics.

     

Chemical Synthesis of Interleukin-2 and Disulfide Stabilizing Analogues

Chemical protein synthesis allows the construction of well-defined structural variations and facilitates the development of deeper understanding of protein structure–function relationships and new protein engineering strategies. Herein, we report the chemical synthesis of interleukin-2 (IL-2) variants on a multimilligram scale and the formation of non-natural disulfide mimetics that improve stability against reduction. The synthesis was accomplished by convergent KAHA ligations; the acidic conditions of KAHA ligation proved to be valuable for the solubilization of the hydrophobic segments of IL-2. The bioactivity of the synthetic IL-2 and its analogues were shown to be equipotent to recombinant IL-2 and exhibit improved stability against reducing agents.     

Auto white balance method using a pigmentation separation technique for human skin color

Optical Review - The human visual system maintains the perception of colors of an object across various light sources. Similarly, current digital cameras feature an auto white balance function,...     

NQR, NMR and Crystal Structure Studies of [C(NH2)3]3Sb2Br9

The crystal structure of [C(NH₂)₃]₃Sb₂Br₉ was determined at 143 K: monoclinic, space group C2/c, Z = 4, a = 15.695 (3), b = 9.039(2), c = 18.364(3) Å, β = 96.94(1)°. The structure consists of two crystallographically independent guanidinium ions and two-dimensional corrugated sheets of (Sb₂Br₉ ^3?) _n , in which SbBr₆ octahedra are connected through three bridging Br atoms each other. One of the cations situates in a cavity of the (Sb₂Br₉ ^3?) _n layer with statistical disorder, while the other situates between the layers without disorder. Three ⁸¹Br NQR resonance lines were assignable to terminal Br atoms, while only one line was found for two inequivalent bridging Br atoms. All the ⁸¹Br NQR resonance lines were subjected to fade-out at low temperatures. The temperature dependence curve of ¹H NMR T ₁ showed well defined two minima, which were explained by postulating the C₃ reorientations of two types of cations with very different activation energies. The DTA (DSC) measurement revealed a phase transition of a first-order type at 444 K.     

Selective collection of inorganic iron(III) colloids in water with oxine-impregnated water-in-oil emulsion

An oxine-impregnated emulsion was prepared by dissolving 100 mg of oxine and 0.3 ml of non-ionic surfactant (Span-80) in 10 ml of toluene and mixing with 3 ml of 1 mol l(-1) hydrochloric acid by sonication (20 kHz). The water-in-oil emulsion was injected into 50 ml of water sample (containing iron(III) at the ppb level, pH 4-7) and dispersed by stirring for 10 min as numerous small globules (0.1-0.5 mm in diameter). The iron diffused through the toluene layer into the small droplets of hydrochloric acid. The emulsion was separated by flotation and heated to segregate the aqueous (hydrochloric acid) and organic (toluene) phases. The iron in the aqueous phase was determined by graphite-furnace atomic absorption spectrometry (GFAAS). Hydrated iron(III) oxide having particle sizes of larger than 1 mum did not penetrate into the emulsion. Other iron species which were not incorporated into the emulsion include humic complexes and hybrid particles of hydrated iron(III) oxide and humic substances. This discrimination can be attributed to the surfactant layer at the oil-water interfaces and gentle stirring of the solution. The conventional liquid-liquid extraction, however, did not offer such a selectivity, because all iron(III) species were simultaneously extracted into the organic phase with vigorous shaking. The unique property of the emulsion method has been applied to the separation and determination of inorganic dissolved iron species in river water.     

Density control of poly(ethylene glycol) layer to regulate cellular attachment

A wide variety of cells usually integrate and respond to the microscale environment, such as soluble protein factors, extracellular matrix proteins, and contacts with neighboring cells. To gain insight into cellular microenvironment design, we investigated two-dimensional microarray formation of endothelial cells on a micropatterned poly(ethylene glycol) (PEG)-brushed surface, based on the relationship between PEG chain density and cellular attachment. The patterned substrates consisted of two regions: the PEG surface that acts as a cell-resistant layer and the exposed substrate surface that promotes protein or cell adsorption. A PEG-brushed layer was constructed on a gold substrate using PEG with a mercapto group at the end of the chain. The density of the PEG-brushed layer increased substantially with repetitive adsorption/rinse cycles of PEG on the gold substrate, allowing marked reduction of nonspecific protein adsorption. These repeated adsorption/rinse cycles were further regulated by using longer (5 kDa) and shorter (2 kDa) PEG to construct PEG layers with different chain density, and subsequent micropatterning was achieved by plasma etching through a micropatterned metal mask. The effects of PEG chain density on pattern formation of cell attachment were determined on micropatterning of endothelial cells. The results indicated that cell pattern formation was strongly dependent on the PEG chain density and on the extent of protein adsorption. Notably, a PEG chain density high enough to inhibit outgrowth of endothelial cells from the cell-adhering region in the horizontal direction could be obtained only by employing formation of a short filler layer of PEG in the preconstructed longer PEG-brushed layer, which prevented nonspecific protein adsorption almost completely. In this way, a completely micropatterned array of endothelial cells with long-term viability was obtained. This clearly indicated the importance of a short underbrushed PEG layer in minimizing nonspecific protein adsorption for long-term maintenance of the active cell pattern. The strategy for cell patterning presented here can be employed in tissue engineering to study cell-cell and cell-surface interactions. It is also applicable for high-throughput screening and clinical diagnostics, as well as interfacing cellular and microfabricated components of biomedical microsystems.     

Synthesis, structure, and reactivity of naphthalyne-Co2(CO)6 complexes

Synthesis of naphthalyne-Co2(CO)6 complexes, the first example of the aryne-Co2(CO)6 complex, was achieved via cyclization of acyclic alkyne-Co2(CO)6 complex precursors containing an allylsilane and an aldehyde moiety followed by dehydration. Unique reactivities of the complexes toward oxygen to give carboxylic acid derivatives and toward alkynes to give cyclopentadienone derivatives were also disclosed.