The high‐pressure form of cadmium vanadate,CdV2O6

The crystal structure of a new high‐pressure modification of cadmium divanadium hexaoxide, CdV₂O₆, was refined from X‐ray single‐crystal data. It contains zigzag chains of edge‐sharing VO₆ octahedra. Octahedra in adjacent chains share corners and form corrugated layers. Octahedrally coordinated Cd atoms, which lie on twofold axes, are situated between the layers. The columbite‐like structure results in a strong distortion of the CdO₆ octahedra which may be stabilized only at high pressure.     

Further test of the isolated pentagon rule: Thermodynamic and kinetic stabilities of C84 fullerene isomers

Thermodynamic and kinetic stabilities of 73 C₈₄ fullerene isomers were estimated from the MM3 heats of formation and the recently defined bond resonance energies (BREs), respectively. The BRE represents the contribution of a given π bond in a molecule to the topological resonance energy (TRE). All π bonds shared by two pentagons turned out to be highly reactive without exceptions. C₈₄ fullerene isomers with such π bonds must be incapable of survival during harsh synthetic processes. Thus, the isolated pentagon rule (IPR) proved to be applicable to such large fullerene cages. For sufficiently large fullerenes like C₈₄, some isolated-pentagon isomers are also predicted to be very unstable with highly antiaromatic π bonds. © 1996 by John Wiley & Sons, Inc.     

Macromolecular helicity inversion of an optically active helical poly(phenylacetylene) by chemical modification of the side groups

An optically active helical poly(phenylacetylene) was synthesized by the copolymerization of phenylacetylenes bearing optically active hydroxy or ester groups obtained by the kinetic resolution of a racemic phenylacetylene with lipase; the helix-sense was inverted from one helix to another by the further chemical modification of the hydroxy groups with achiral bulky isocyanates or an acid chloride.     

Simultaneous detection of N-terminal fragment ions in a protein mixture using a ruthenium(II) complex

Use of a bis(terpyridine)ruthenium(II) derivative as an N-terminal labeling reagent resulted in the simultaneous detection and individual determination of all the N-terminal fragments of the proteins in a mixture without requiring any separation. All of the N-termini of the guanidinated proteins were labeled selectively by the ruthenium complex (-CO-labeling). After chymotryptic digestion, the fragments were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and post-source decay (PSD). The -CO moiety exclusively enhanced N-terminal fragment ions in mass spectra and enabled easy N-terminal sequencing. In a mixture containing three different proteins (lysozyme, ubiquitin, and insulin), all of the N-terminal fragment ions labeled with the ruthenium complex were found to produce uniformly intense peaks without the detection of the other unlabeled fragments. The N-terminal sequences of these ions were determined individually by PSD analysis. Application to unknown proteins from Thermus thermophilus HB8 with two-dimensional electrophoretic separation resulted in the successful determination of the N-terminal sequence and easy identification of the target protein.     

Tuning the Reactivity of a Substrate for SNAP-Tag Expands Its Application for Recognition-Driven DNA-Protein Conjugation

Recognition-driven modification has been emerging as a novel approach to modifying biomolecular targets of interest site-specifically and efficiently. To this end, protein modular adaptors (MAs) are the ideal reaction model for recognition-driven modification of DNA as they consist of both a sequence-specific DNA-binding domain (DBD) and a self-ligating protein-tag. Coupling DNA recognition by DBD and the chemoselective reaction of the protein tag could provide a highly efficient sequence-specific reaction. However, combining an MA consisting of a reactive protein-tag and its substrate, for example, SNAP-tag and benzyl guanine (BG), revealed rather nonselective reaction with DNA. Therefore new substrates of SNAP-tag have been designed to realize sequence-selective rapid crosslinking reactions of MAs with SNAP-tag. The reactions of substrates with SNAP-tag were verified by kinetic analyses to enable the sequence-selective crosslinking reaction of MA. The new substrate enables the distinctive orthogonality of SNAP-tag against CLIP-tag to achieve orthogonal DNA-protein crosslinking by six unique MAs.     

Construction of Helical Structures with Multiple Fused Anthracenes: Structures and Properties of Long Expanded Helicenes

Polycyclic aromatic compounds consisting of four or five fused anthracene units were synthesized by PtCl₂-catalyzed cycloisomerization as novel long expanded helicenes. These compounds have helical structures with significant stacking of the terminal anthracene moieties at 0.33 nm interlayer distance. In the UV-vis and fluorescence spectra, the absorption and emission bands were red-shifted as the number of fused anthracene units was increased. The characteristic broad and long-lived emission bands of the long analogues are explained by the excimer-like stabilization of the excited state. These photophysical data as well as their cyclic voltammetric data are discussed on the basis of the π-conjugation and interlayer π⋅⋅⋅π interactions in the molecular structures and the molecular orbitals. The barrier and mechanism of helical inversion are also reported.     

Synthesis of perfluorobicyclic ethers

The electrochemical fluorination of cycloalkyl-substituted acetic and propionic acids were conducted to obtain several kinds of perfluorobicyclic ethers [reaction conditions: Anodic current density: 3.5 A/dm², Volt: 5～8V, Temp: 5～6 °C] . For example, from cyclopentyl-substituted acetic acids, perfluoro(4-alkyl-2-oxabicyclo[3.3.0]octane)s (I) were formed as the cyclization products in yields of 10～19% together with the corresponding perflouroalkanoyl flourides (II) (Y=3～13%).

While, perfluorospiro-ethers were obtained from the fluorination of 3-cycloalkyl-substituted propionic acids. The characterization of these perfluorobicyclic ethers which consists of the reaction with anhydrous aluminum chloride will be reported also.