Metal-induced regulation of fullerene complexation with double-calix[5]arene

The metal-induced regulation of fullerene complexation with double-calix[5]arene is described. The receptor shows strong binding to C70 only in the presence of Cu+.     

Memory effect on the glass transition in vulcanized rubber

The memory effect upon glassification is studied in the glass-to-rubber transition of vulcanized rubber with the strain as a controlling parameter. A phenomenological model is proposed, taking the history of the temperature and the strain into account, by which the experimental results are interpreted. The data and the model demonstrate that the glassy state memorizes the time course of strain upon glassification, not as a single parameter but as the history itself. The data also show that the effect of irreversible deformation in the glassy state is beyond the scope of the present model.     

syn-selective direct catalytic asymmetric Mannich-type reactions of hydroxyketones using Y{N(SiMe3)2}3/linked-BINOL complexes

[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield).     

Phase diagram of the square-lattice three-state Potts antiferromagnet with a staggered polarization field

We study a square-lattice three-state Potts antiferromagnet with a staggered polarization field at finite temperature. Numerically treating the transfer matrices, we determine two phase boundaries separating the model-parameter space into three parts. We confirm that one of them belongs to the ferromagnetic three-state Potts criticality, which is in accord with a recent prediction, and another to the Ising-type; these are both corresponding to the massless renormalization-group flows stemming from the Gaussian fixed points. We also discuss a field theory to describe the latter Ising transition.     

Schulzeines A-C, new alpha-glucosidase inhibitors from the marine sponge Penares schulzei

Three new alpha-glucosidase inhibitors, schulzeines A-C (1-3), were isolated from the marine sponge Penares schulzei. Their structures were elucidated by spectral analysis and chemical degradations to be the isoquinoline alkaloids, encompassing two amino acids, and C(28) fatty acid, the last of which was sulfated. Absolute stereochemistry of schulzeines was determined by application of the modified Mosher analysis to fragments obtained by chemical degradation. Schulzeines A-C inhibit alpha-glucosidase with IC(50) values of 48-170 nM.     

Contributions of short-range and excluded-volume interactions to unperturbed polymer chain dimensions

A Monte Carlo study is made of the mean-square radius of gyration for the freely rotating chain with such fictitious excluded-volume interactions that the Lennard-Jones 6-12 potentials at the Theta temperature act only between the fourth-through (3+Delta)th-neighbor beads (Delta > or = 1) along the chain. The behavior of the asymptotic value (/n)infinity of the ratio /n as a function of the number n of bonds in the chain in the limit of n --> infinity is examined as a function of Delta. It is shown that the approach of (/n)infinity to its value for the real unperturbed chain with Delta = infinity is so slow that the interactions between even up to about 100th-neighbor beads should be taken into account in order to reproduce nearly its dimension. The result implies that the unperturbed polymer chain dimension as experimentally observed at the Theta temperature depends not only on short-range interactions but also to a considerable extent on the long-range excluded-volume interactions, and that the asymptotic value Cinfinity of the characteristic ratio Cn for the rotational isomeric state model in the limit of n --> infinity, which is determined only by the very local conformational energy, cannot be directly compared with the corresponding experimental value.     

Screening effect diverts the swimming directions from diaphototactic to positive phototactic in a disk-shaped green flagellate Mesostigma viride

We found diaphototactic behavior (i.e. the cells swim perpendicularly with respect to the incident light) in a strain with colorless eyespot of a unicellular disk-shaped green flagellate Mesostigma viride. Lacking pigments completely in the eyespot, the screening effect in this strain was due only to the central part of the chloroplast whose cross section was thin. The diaphototaxis was most obvious when unilateral green stimulus light (520-580 nm) was given, whereas positive phototaxis appeared when given blue light (430-490 nm). The choice between diaphototaxis and (ordinary) phototaxis depended entirely on the transmission (%T) of the cell body against each wavelength of the stimulus: the green light penetrated well (%T > 90%), whereas the blue light was considerably shaded by the chloroplast (50% < %T < 70%). The fraction of positive phototactically behaving cells against each wavelength was in proportion to the front-to-back contrast value obtained at each individual wavelength. The fraction of diaphototaxis was inversely proportional to it. In addition, bilateral stimulus irradiations to wild-type cell with colored eyespot provided useful information about the principle of the diaphototactic steering.     

Acid-catalyzed transformation of rubrene to indenonaphthacene and its paired interacting orbital (PIO) analysis

Treatment of rubrene (5,6,11,12-tetraphenylnaphthacene) with trifluoroacetic acid in dichloromethane gives 4b,9,10-triphenyl-4b,9-dihydroindeno[1,2,3-fg]naphthacene (1) as the sole isolable product. Paired interacting orbital (PIO) analysis indicates that the reaction is initiated by preferential attack of H⁺ at C(11) position of rubrene.