Stereochemie der Copolymerisation von optisch aktivem 3-Phenyl-1,2-epoxypropan mit CO2

Ohne Zusammenfassung     

Factors controlling the complex architecture of native and modified cyclodextrins with dipeptide (Z-Glu-Tyr) studied by microcalorimetry and NMR spectroscopy: critical effects of peripheral bis-trimethylamination and cavity size

Complex stability constant (K), standard free energy (DeltaG degrees ), reaction enthalpy (DeltaH degrees ), and entropy change (TDeltaS degrees ) for 1:1 inclusion complexation of the diastereomeric dipeptides Z-d/l-Glu-l-Tyr (Z = benzyloxycarbonyl) and its component amino acids (Z-d/l-Glu and N-Ac-Tyr) with native alpha-, beta-, and gamma-cyclodextrins (CDs) and A,X-modified bis(6-trimethylammonio-6-deoxy)-beta-CDs (AX-TMA(2)-beta-CDs) were determined in buffer solution (pH 6.9) at T = 298.15 K by isothermal titration microcalorimetry. Concurrent NMR spectral examinations revealed that the penetration mode and the resulting complex architecture are dramatically altered by the peripheral modification and also by the CD's cavity size. Upon complexation of the ditopic Z-Glu-Tyr guest, native alpha- and beta-CDs preferentially bind the Z's phenyl group, whereas AX-TMA(2)-beta-CDs predominantly include the Tyr's phenol moiety. In contrast, native gamma-CD includes both of the aromatic moieties simultaneously in the same cavity. Furthermore, for isomeric AB-, AC, and AD-TMA(2)-beta-CDs, an inversion of enantioselectivity and a switching of the penetration mode were observed, critically depending on the position of TMA substituents.     

Organic layered crystals with adjustable interlayer distances of 1-naphthylmethylammonium n-alkanoates and isomerism of hydrogen-bond networks by steric dimension

A series of 1-naphthylmethylammonium n-alkanoates from acetate to triacontanoate produce isomorphic layered structures in the crystalline state. The interlayer distances, d-spacings, are proportional to the lengths of the alkyl chains. This is attributed to synergic intermolecular interactions; pi-pi and CH-pi interactions of the naphthalene rings between the cations, hydrophobic interactions of the alkyl chains, and two-dimensional hydrogen-bond networks between the primary ammonium cations and the carboxylate anions. Salts made from carboxylic acids wider than 5.5 A in the cross sections produce another columnar structure with a one-dimensional ladder-type hydrogen-bond network. Steric parameters of the acid components provide an explanation for the isomerism of the hydrogen-bond network.     

Novel cofacial oxidative coupling reaction of phosphinine in the presence of CuI and ClO4-

2,4,6-triphenylphosphinine (TPP) underwent unprecedented cofacial oxidative coupling to form a novel C2-symmetric cage compound, having extremely long C-C bonds.     

Single-photon detector for long-distance fiber-optic quantum key distribution

We have investigated the performance of an InGaAs/InP avalanche photodiode for photon counting at 1550 nm in the temperature range of thermoelectric cooling. A quantum efficiency of 13.7% was obtained at -55 degrees C , while the dark-count probability per gate (?1 ns) was kept as small as 2.4x10(-5) . The developed single-photon detector would yield a 104.4-km fiber-optic quantum key distribution in the ideal condition.     

Analysis of single-cell differences by use of an on-chip microculture system and optical trapping

A method is described for continuous observation of isolated single cells that enables genetically identical cells to be compared; it uses an on-chip microculture system and optical tweezers. Photolithography is used to construct microchambers with 5-microm-high walls made of thick photoresist (SU-8) on the surface of a glass slide. These microchambers are connected by a channel through which cells are transported, by means of optical tweezers, from a cultivation microchamber to an analysis microchamber, or from the analysis microchamber to a waste microchamber. The microchambers are covered with a semi-permeable membrane to separate them from nutrient medium circulating through a "cover chamber" above. Differential analysis of isolated direct descendants of single cells showed that this system could be used to compare genetically identical cells under contamination-free conditions. It should thus help in the clarification of heterogeneous phenomena, for example unequal cell division and cell differentiation.