Drying dissipative structures of the aqueous suspensions of monodisperse bentonite particles

Macroscopic and microscopic dissipative structural patterns formed in the course of drying the fractionated and monodisperse bentonite particles (plate-like in their shape) in aqueous deionized suspension and in the presence of NaCl have been studied on a cover glass. The patterns coexisted with the broad ring of the hill accumulated with the particles and with the round hills are formed around the outside edges of the film and in the center, respectively, in the macroscopic scale. By the addition of NaCl the pattern shifts from the broad ring to the round hill in the center. The spoke-like cracks, which have been observed for the suspensions of the spherical particles so often hitherto, are not observed at all for the bentonite suspensions. The characteristic convection flow of the particles and the interactions among the particles and substrate are important for the macroscopic pattern formation. Wrinkled, branch-like and/or star-like fractal patterns are observed in the microscopic scale. These patterns are determined mainly by the electrostatic and polar interactions between the particles and/or between the particle and the substrate in the course of drying.     

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.     

The effect of phenoxy oxygen atoms on extremely high extraction ability and less separation efficiency of trivalent rare earth elements with tetraphosphonic acid derivative of calix[4]arene

A cone confomational p-t-octylcalix[4]arene with four methylenephosphonic acids at the lower rim as well as its monomeric analog have been synthesized as a new extraction reagent to investigate the extraction behavior of the nine trivalent rare earth elements: Y, La, Pr, Nd, Sm, Eu, Gd, Ho and Er. The new calix[4]arene exhibited significantly higher extraction capacity than not only the monomeric derivative and the commercial extraction reagent, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate, but also the cone conformational calix[4]arene extractants employed in our previous work, composed of a tetrapropylenephosphonic acid with a longer spacer, a tetraphosphonic acid at the upper rim, and tetraacetic acid at the lower rim. A dependence on the pH was observed for the new extractant in the highly acidic region, and the extraction took place via a simple ion-exchange mechanism. Using slope analysis, the stoichiometries of tetrameric and monomeric extractants to rare earth metal ions were determined to be 2:1 and 3:1, respectively. Using the proposed extraction equations, extraction equilibrium constants and separation factors were estimated. The extremely high extraction ability and moderate separation efficiency were attributed to the chelating effect of the phosphonic acid and the phenoxy oxygen atom. The effect of the phenoxy oxygen atom on extraction ability and separation efficiency of calix[4]arene derivatives was found to be significant.     

Kinetic Resolution of Racemic Secondary Benzylic Alcohols by the Enantioselective Esterification Using Pyridine‐3‐carboxylic Anhydride (3‐PCA) with Chiral Acyl‐Transfer Catalysts

Pyridine‐3‐carboxylic anhydride (3‐PCA) was found to function as an efficient coupling reagent for the preparation of carboxylic esters from various carboxylic acids with alcohols under mild conditions by a simple experimental procedure. This novel condensation reagent 3‐PCA was applicable not only for the synthesis of achiral carboxylic esters catalyzed by 4‐(dimethylamino)pyridine (DMAP) but also for the production of chiral carboxylic esters by the combination of chiral nucleophilic catalyst, such as tetramisole (=2,3,5,6‐tetrahydro‐6‐phenylimidazo[2,1‐b][1,3]thiazole) derivatives. An efficient kinetic resolution of racemic benzylic alcohols with achiral carboxylic acids was achieved by using 3‐PCA in the presence of (R)‐benzotetramisole ((R)‐BTM), and a variety of optically active carboxylic esters were produced with high enantiomeric excesses by this new chiral induction system without using a tertiary amine.     

Affinity of Hemicellulose for Cellulose Produced by Acetobacter Xylinum

Cellulose composites were produced by culturing Acetobacter aceti subsp. xylinum (ATCC 53524, agitation tolerant strain) under shaking and agitating conditions in the presence of 2% pine or beech Björkman lignin-carbohydrate complexes (LCCs) or six different types of hemicellulosic polysaccharides including glucuronoxylan, glucomannan, O-acetyl-glucuronoxylan, arabinoglucuronoxylan, arabinogalactan and xyloglucan. Hemicellulosic polysaccharide contents in cellulose composites were similar in spite of the differences in culture, shaking and agitating conditions. On the basis of hemicellulosic polysaccharide contents and X-ray diffraction patterns after extraction by dilute NaOH solution, glucomannan family polysaccharides were found to have the highest affinity to bacterial cellulose. Composites with neutral and acidic LCCs were resistant against alkali while high lability of their delignified carbohydrates against alkali indicates the importance of lignin for formation of cellulose-hemicellulose-lignin framework of plant secondary cell-walls.     

Highly regioselective nucleophilic carbon-carbon bond formation on furans and thiophenes initiated by pummerer-type reaction

[reaction: see text] The reactions of (phenylsulfinyl)furans or -thiophenes with carbon nucleophiles in the presence of trifluoroacetic anhydride allowed the nucleophilic installation of carbon functional groups on the furan and thiophene nuclei with complete regioselectivity.     

Total synthesis of citridone A

The first total synthesis of citridone A has been achieved through regioselective intramolecular iodocyclization and regio- and stereoselective Pd(0)-catalyzed coupling as key reactions.     

The cellulose system in viscin from mistletoe berries

The cellulose system of the viscous fibrous cellulosic polysaccharide (viscan) in the viscin tissue of the European mistletoe, Viscum album L., was analyzed by chemical and physicochemical techniques including sugar analysis, optical and transmission electron microscopy, X-ray and electron diffraction together with solid state CP/MAS ¹³C-NMR spectroscopy. The results confirmed that in the elongated thin viscin cells, the cellulose microfibrils (having a diameter of around 3 nm) were tightly coiled with their axes perpendicular to the long axis of the cell. Upon stretching these cells became deformed by more than a hundred fold. In such a deformation, the cellulose microfibrils became unwound to be perfectly aligned along the stretching direction. Based on solid-state CP/MAS ¹³C-NMR spectroscopic analysis of the viscin tissue, it was found that its cellulose consisted of I and I polymorphs in the ratio 1:1.