D3h‐Symmetric Porphyrin‐Based Rigid Macrocyclic Ligands for Multicofacial Multinuclear Complexes in a One‐Nanometer‐Sized Cavity

The one‐step synthesis of D_3h‐symmetric cyclic porphyrin trimers 1 composed of three 2,2′‐[4,4′‐bis(methoxycarbonyl)]bipyridyl moieties and three porphyrinatozinc moieties was achieved from a nickel‐mediated reductive coupling of meso‐5,15‐bis(6‐chloro‐4‐methoxycarbonylpyrid‐2‐yl)porphyrinatozinc. Although cyclic trimers 1 were obtained as a mixture that included other cyclic and acyclic porphyrin oligomers, an extremely specific separation was observed only for cyclic trimers 1 when using columns of silica gel modified with pyrenylethyl, cyanopropyl, and other groups. Structural analysis of cyclic trimers 1 was carried out by means of NMR spectroscopy and X‐ray crystallography. Treatment of an η³‐allylpalladium complex with a cyclic trimer gave a tris(palladium) complex containing three η³‐allylpalladium groups inside the space, which indicated that the bipyridyl moieties inside the ring could work as bidentate metalloligands.     

Reversible electro-optical switching of a memory type PDLC using two-frequency-addressing liquid crystals

Abstract

A memory type PDLC has been prepared by sandwiching a mixture of two-frequency-addressing liquid crystals and acrylate monomers with a hydoroxy group between two glass substrates with ITO electrodes followed by UV irradiation. This PDLC can be electrically switched between a transparent state and a light scattering state, which are maintained over several months without electric fields.     

Cloning and Characterization of Fructosamine-6-Kinase from Arthrobacter aurescens

Fructosamine-6-kinases (FN6Ks) that catalyze phosphorylation of glycated amino acids, i.e., fructosyl amino acids (FAs), have been shown as a potential recognition element for glycated protein detection. However, there are only two available FN6Ks: those from Escherichia coli which is specific for ε-fructosyl lysine (ε-FK) and Bacillus subtilis which recognizes both ε-FK and α-FA as substrates. In this study, we characterized an FN6K homologue isolated from Arthrobacter, some of whose species are reported to assimilate FA. The BLAST searches of Arthrobacter genomic database, using the bacterial FN6K primary structure information, revealed the presence of an FN6K homologue in Arthrobacter aurescens TC1 strain. Indeed, enzymatic assays confirmed that the putative FN6K from A. aurescens is an FN6K that is specific for ε-FK, although the primary sequence alignments showed similarity of A. aurescens FN6Ks with FN6Ks from B. subtilis and E. coli at the same level. In this study, we describe for the first time the presence of FN6K in Arthrobacter spp. and ε-FK-specific degradation pathway from Gram-positive bacteria, providing important information for the development of FA-recognizing molecules as well as for the FA assimilation system in bacteria.     

Neomacrophorin I,II, and III,novel drimenyl cyclohexanes with hydroxylated butanoates from Trichoderma sp. 1212-03

Neomacrophorins I (1), II (2), and III (3) were isolated from the culture broth of Trichoderma sp. 1212-03, which was collected at Shirakami Mountainous area in Japan. Structural analyses disclosed that these resemble known macrophorins but possess axial-hydroxy group at C3 as well as different side chains at C7′. These are diastereomeric forms of macrophorins for 5′,6′-epoxide functionality. The NMR analyses suggested their relative configurational relationship between the C1–C15 drimene and C1′–C7′ epoxyquinone moieties. ECD spectral discussions verified them particularly for C5′,C6′-epoxyquinone (1), C5′,C6′-epoxysemiquinone (2 and 3), and 2″,3″-dihydroxybutanoate moiety in 1 and 2. The configuration of C3″-stereocenter of 3 was determined by chiral GC–MS after converting into methyl (S)-3″-hydroxybutanoate by basic of 3 methanolysis. Biological assays disclosed that 1 induces hyphal branching of Cochliobolus miyabeanus as well as cytotoxicity against human colorectal cancer COLO 201.     

2′,4′-BNA/LNA with 9-(2-Aminoethoxy)-1,3-diaza-2-oxophenoxazine Efficiently Forms Duplexes and Has Enhanced Enzymatic Resistance**

Artificial nucleic acids are widely used in various technologies, such as nucleic acid therapeutics and DNA nanotechnologies requiring excellent duplex-forming abilities and enhanced nuclease resistance. 2′-O,4′-C-Methylene-bridged nucleic acid/locked nucleic acid (2′,4′-BNA/LNA) with 1,3-diaza-2-oxophenoxazine (BNAP ( B^H )) was previously reported. Herein, a novel B^H analogue, 2′,4′-BNA/LNA with 9-(2-aminoethoxy)-1,3-diaza-2-oxophenoxazine (G-clamp), named BNAP-AEO ( B^AEO ), was designed. The B^AEO nucleoside was successfully synthesized and incorporated into oligodeoxynucleotides (ODNs). ODNs containing B^AEO possessed up to 10⁴-, 152-, and 11-fold higher binding affinities for complementary (c) RNA than those of ODNs containing 2′-deoxycytidine ( C ), 2′,4′-BNA/LNA with 5-methylcytosine ( L ), or 2′-deoxyribonucleoside with G-clamp ( P^AEO ), respectively. Moreover, duplexes formed by ODN bearing B^AEO with cDNA and cRNA were thermally stable, even under molecular crowding conditions induced by the addition of polyethylene glycol. Furthermore, ODN bearing B^AEO was more resistant to 3′-exonuclease than ODNs with phosphorothioate linkages.     

Influence of laser fluence and irradiation timing of F2 laser on ablation properties of fused silica in F2-KrF excimer laser multi-wavelength excitation process

A collinear irradiation system of F₂ and KrF excimer lasers for high-quality and high-efficiency ablation of hard materials by the F₂ and KrF excimer lasers’ multi-wavelength excitation process has been developed. This system achieves well-defined micropatterning of fused silica with little thermal influence and little debris deposition. In addition, the dependence of ablation rate on various conditions such as laser fluence, irradiation timing of each laser beam, and pulse number is examined to investigate the role of the F₂ laser in this process. The multi-wavelength excitation effect is strongly affected by the irradiation timing, and an extremely high ablation rate of over 30 nm/pulse is obtained between -10 ns and 10 ns of the delay time of F₂ laser irradiation. The KrF excimer laser ablation threshold decreases and its effective absorption coefficient increases with increasing F₂ laser fluence. Moreover, the ablation rate shows a linear increase with the logarithm of KrF excimer laser fluence when the F₂ laser is simultaneously irradiated, while single KrF excimer laser ablation shows a nonlinear increase. The ablation mechanism is discussed based on these results. Received: 16 July 2001 / Accepted: 27 July 2001 / Published online: 2 October 2001     

A practical synthesis of archaeosine and its base

A practical synthetic route to 7-formamidino-7-deazaguanosine (archaeosine), a hypermodified nucleoside observed in archaeal tRNA, has been developed, which involves the addition of hydroxylamine to the cyano group of 7-cyano-7-deazaguanosine (preQ₀-nucleoside) and a subsequent Pd-catalyzed hydrogenation. PreQ₀-nucleoside was obtained from an optimized β-selective glycosylation developed by Hocek et al. The corresponding archaeosine base was subsequently synthesized in high yield from its precursor 7-cyano-7-deazaguanine (preQ₀).     

Single-particle light scattering study of polyethyleneglycol-grafted poly(ureaurethane) microcapsule in ethanol

Microcapsules having polyethyleneglycol-grafted poly(ureaurethane) (PUU) membrane and di-2ethylhexyl phthalate core have been prepared, and the structure when they were suspended in dispersing ethanol have been studied by means of single-particle light scattering method. The PUU membrane was synthesized from monomers with aromatic functional groups (microcapsule MC110) and hexamethylene functional groups (microcapsule MC160). Because the outer and inner solvent passed through the membrane easily, the outside and inside of the membrane were the same at the equilibrium state. The thickness of the wall membrane was significantly smaller than that calculated from the overall weight ratio of the wall-forming material and the core solvents. It was attributed to low affinity of PUU membranes and ethanol.