Single crystals of amylose V complexes. III. Crystals with 81 helical configuration

Single crystals of amylose V complexes with the 8₁ helical configuration can be obtained from aqueous solutions of amylose by using α-naphthol as a complexing agent. Morphological observations suggest that the differences in crystallization behavior among the α-naphthol complex and other complexes with alcohols are due to differences in solubility of the complexes in water. Electron diffraction studies indicate a two-dimensional tetragonal unit cell with a = b = 22.9 Å. It is deduced that the space group providing a satisfactory arrangement of two helices is one of the enantiomorphs P4₁2₁2 and P4₃2₁2. From x-ray diffraction it was found that the c axis spacing of the α-naphthol complex is equivalent to that in 6₁ and 7₁ helical amylose crystals. Consequently, the geometry of the helical configuration requires an integral number of glucose residues per turn. The true helical diameters of the n-butanol, isopropanol, and α-naphthol complexes were calculated from experimental data. The ratio was 6:7:8 and indicated that the helix of the α-naphthol complex has eight glucose residues per turn. The diversity of helical configurations in V amylose crystals is discussed.     

Memory effects on the quantum diffusion of a particle in a fluctuating medium

We introduce a phenomenological Hamiltonian for a particle in a medium with sitediagonal and off-diagonal disorder. Without assuming the usual white noise expression for the correlation between fluctuating variables, we arrive at a master equation using second order perturbation theory. This expression is expanded in powers of the correlation time. The mean square displacement and velocity are discussed and corrections to the diffusion coefficient are given.Partially supported by the grant of the Ministry of Education of the Japanese Government and by Sakkokai Foundation     

Spectra and emission lifetimes of H2CS(Ã 1A2)

Fluorescence spectra and lifetimes of single vibronic levels of the first excited singlet state of H₂CS have been measured under effusive flow conditions. Fluorescence lifetimes of the single vibronic levels decrease from 140±3 μs (0°) to 68 μs(3¹4¹5¹) with increasing excitation energies. The promoting vibrational modes for the non-radiative transition are considered to be the out-of-plane bending (ν₄) and the asymmetric rocking (ν₆) modes rather than the asymmetric stretching mode (ν₅).     

Parallel vs. anti-parallel orientation in a curdlan/oligo(dA) complex as estimated by a FRET technique

We already found that beta-1,3-glucan polysaccharides form polymeric complexes with certain polynucleotides, but the parallel vs. anti-parallel orientation in those complexes had remained unsolved. In this paper, this controversial problem has been discussed for curdlan/oligo(dA) complexes utilizing two different energy transfer techniques. The first system consists of a combination of fluorescein-labeled curdlan and 3'-(or 5'-)tetramethyl-rhodamine (TAMRA)-labeled oligo(dA). The second system utilizes gold nanoparticles: that is, two curdlan chains were linked by a disulfide bond and after complexation with oligo(dA), the complex was immobilized on gold nanoparticles. In this system, TAMRA was attached to the 3'(or 5') end of oligo(dA) and the gold particle acted as a fluorescence quencher (energy acceptor). These experiments have led us to conclude that in the curdlan/oligo(dA) complex, parallel orientation is more favourable than anti-parallel orientation. These findings have enabled us to envision a clearer image for the complexation mode between beta-1,3-glucan polysaccharides and polynucleotides.     

Experimental investigation of a nonideal two-qubit quantum-state filter by quantum process tomography

We used quantum process tomography to investigate and identify the function of a nonideal two-qubit quantum-state filter subject to various degrees of decoherence. We present a simple decoherence model that explains the experimental results and point out that a beam splitter followed by a postselection process is not, as commonly believed, a singlet-state filter. In the ideal case it is a triplet-state filter.     

Chiral phosphinooxazolidine ligands for palladium- and platinum-catalyzed asymmetric Diels-Alder reactions

Cationic palladium (Pd)- and platinum (Pt)-phosphinooxazolidine catalysts 13a-c, 15a-d, 17a-c, and 19a-c were prepared from phosphinooxazolidine ligands 1-3, MCl(2) (M = Pd and Pt), and counterions, and the activities of the catalysts in the asymmetric Diels-Alder (DA) reactions of cyclic or acyclic dienes with imide dienophiles were investigated. These catalysts demonstrated high levels of catalytic activity. The cationic Pd-POZ complex 13c provided particularly excellent enantioselectivity (98% ee) in the DA reactions of cyclopentadiene with acryloyl-, crotonyl-, and fumaroyl-1,3-oxazolidin-2-ones (20a-c).     

Enhancement of water solubility of fullerene by cogrinding with mixture of cycloamyloses, novel cyclic alpha-1,4-glucans, via solid-solid mechanochemical reaction

Improvement of solubility for fullerene (C60) was studied by cogrinding with cycloamyloses using a ball mill in the solid state. Cycloamylose is a novel cyclic alpha-1,4-glucan produced from synthetic amylose by enzymatic reaction. Although sample solutions showed a pale yellow for the initial period of cogrinding with cycloamyloses and C60, the color varied to brown after 48 h. Subsequently, the solubility of C60 was improved markedly to 560 (microg/ml) at 96 h. From powder X-ray diffraction analysis, the peak intensity of crystalline C60 decreased as the cogrinding time was extended. The UV-VIS absorption spectrum of C60 shows absorption bands at 262 and 340 nm in water with cycloamyloses, and 258 and 328 nm in n-hexane. These results suggested that C60 molecules were dispersed into cycloamyloses micellar system and the red-shift of the UV-VIS spectra was due to an intermolecular interaction between C60 and cycloamyloses.