Synthesis of gamma-hydroxybutenolides applying crossed aldol condensation in the presence of a bulky lewis acid and their anti-tumor activity

An improved synthesis of gamma-hydroxybutenolides 1a-d was achieved via crossed aldol condensation between aldehydes 2a-d and the protected gamma-hydroxy-beta-methylbutenolides 3 or 4 using the bulky Lewis acid, aluminum tris(2,6-diphenylphenoxide) (ATPH). Using this same methodology, the gamma-hydroxybutenolides 17a-d having various heteroaromatic rings were synthesized and their anti-tumor activities were evaluated.     

Preparation of fritless capillary using avidin immobilized magnetic particles for electrochromatographic chiral separation

In capillary electrochromatography (CEC), magnetic particles (MPs) were packed in a fused silica capillary by using the magnetic field to be retained without frits. For a chiral CEC separation, avidin was immobilized onto the surface of the MPs (AVI-MPs) as a stationary phase by using the physical adsorption technique. The injected AVI-MPs into the capillary were stably captured with the magnet (surface magnetic flux density, 250 mT) under the separation voltage of 10 kV (190 V/cm). By employing the fritless AVI-MPs packed capillary, the chiral separation of ketoprofen was successfully attained with the packing length of only 5 cm. Effects of the modification condition of avidin, pH of background solution, and the packing length on the enantioseparation were also investigated. Under the optimal condition, furthermore, the repeatability for the retention time of ketoprofen was better than 1.5% in the relative standard deviation and the capillary-to-capillary reproducibility was also acceptable in the prepared fritless capillaries.     

Training native English speakers to identify Japanese vowel length contrast with sentences at varied speaking rates

Native English speakers were trained to identify Japanese vowel length in three types of training differing in sentential speaking rate: slow-only, fast-only, and slow-fast. Following Pisoni and Lively's high phonetic variability hypothesis [Pisoni, D. B., and Lively, S. E., Speech Perception and Linguistic Experience, 433-459 (1995)], higher stimulus variability by means of training with two rates was hypothesized to aid learners in adapting to speech rate variation more effectively than training with only one rate. Trained participants identified the length of the second vowel of disyllables, short or long, embedded in a sentence of the respective rate, and received immediate feedback. The three trained groups' abilities before and after training were examined with tests containing sentences of slow, normal, and fast rates, and were compared with those of a control that was not trained. A robust effect of slow-fast training, a marginal effect of slow-only training, but no significant effect of fast-only training were found in the overall test scores. Slow-fast and slow-only training showed small advantages over fast-only training on the fast-rate test scores, while effects for all three training types were found on the slow- and normal-rate test scores. The degree to which the results support the high phonetic variability hypothesis is discussed.     

Transglutaminase-mediated synthesis of a DNA-(enzyme)n probe for highly sensitive DNA detection

A new synthetic strategy for DNA-enzyme conjugates with a novel architecture was explored using a natural cross-linking catalyst, microbial transglutaminase (MTG). A glutamine-donor substrate peptide of MTG was introduced at the 5-position on the pyrimidine of deoxyuridine triphosphate to prepare a DNA strand with multiple glutamine-donor sites by polymerase chain reaction (PCR). A substrate peptide that contained an MTG-reactive lysine residue was fused to the N terminus of a thermostable alkaline phoshatase from Pyrococcus furiosus (PfuAP) by genetic engineering. By combining enzymatically the substrate moieties of MTG introduced to the DNA template and the recombinant enzyme, a DNA-(enzyme)(n) conjugate with 1:n stoichiometry was successfully obtained. The enzyme/DNA ratio of the conjugate increased as the benzyloxycarbonyl-L-glutaminylglycine (Z-QG) moiety increased in the DNA template. The potential utility of the new conjugate decorated with signaling enzymes was validated in a dot blot hybridization assay. The DNA-(enzyme)(n) probe could clearly detect 10(4) copies of the target nucleic acid with the complementary sequence under harsh hybridization conditions, thereby enabling a simple detection procedure without cumbersome bound/free processes associated with a conventional hapten-antibody reaction-based DNA-detection system.     

Redox-responsive conformational alteration of aromatic amides bearing N-quinonyl system

Redox-induced conformational alteration of N-aryl-N-phenylamides, in which the N-aryl group consists of a hydroquinone–p-quinone system, was examined. The reduced form bearing a dihydroxyphenyl or dimethoxyphenyl group exists mainly in the E-form, whereas the oxidized form bearing a N-benzoquinone moiety takes the Z-form both in the crystal and in solution. This redox-induced conformational alteration is associated with a marked change in optical properties. This system appears to have suitable properties for use in external redox stimulus-responsive functional switching.     

Hapalocyclamide: a novel phytotoxic hexapeptide of the cyanobacterium Hapalosiphon sp.

Hapalocyclamide, a novel oxazole-, thiazole- and thiazoline-containing cyclic hexapeptide, was isolated from the terrestrial cyanobacterium Hapalosiphon sp., and which showed phytotoxic activity on lettuce seedling growth. The gross structure of hapalocyclamide was established from spectroscopic data and chemical degradation. The absolute stereochemistry was determined by Marfey’s analysis. Hapalocyclamide was established as cyclo-thiazole-l-alanine-oxazole-d-alanine-d-thiazoline-d-phenylalanine.     

Hydrogen gas-sensing properties of Pt/WO<Subscript>3</Subscript> thin film in various measurement conditions

A well-known gasochromic material is Pt particle-dispersed tungsten trioxide (Pt/WO₃). Its optical properties could make it effective as a hydrogen gas sensor. In this study, Pt nanoparticle-dispersed WO₃ thin films were prepared using the sol–gel process, and their optical and electrical properties dependent on the working environment (i.e., temperature, hydrogen gas concentration, oxygen partial pressure, etc.) were investigated. The Pt/WO₃ thin films prepared at 400 °C showed the largest change in optical transmittance and electrical conductivity when exposed to hydrogen gas compared with the films prepared at other temperatures. The optical absorbance and electrical conductivity were found to be dependent on the hydrogen and oxygen gas concentration in the atmosphere because generation and disappearance of W⁵⁺ in the thin films depend on the equilibrium reaction between injection and rejection of H⁺ into and from the thin films. In addition, the equilibrium reaction depends on the hydrogen and oxygen gas concentrations.     

Degradation of Target Oligosaccharides by Anthraquinone–Lectin Hybrids with Light Switching

Anthraquinone–lectin hybrids were effectively synthesized using water‐soluble anthraquinone derivative 11 with concanavalin A (ConA) and hygrophorus russula lectin (HRL) to give anthraquinone–ConA ( 16 ) and anthraquinone–HRL ( 17 ) hybrids, respectively. These anthraquinone–lectin hybrids effectively and selectively degraded oligosaccharides containing a mannose residue as a non‐reducing terminal sugar, which has affinity for ConA and HRL, under photo‐irradiation with long‐wavelength UV light without additives and under neutral conditions. In addition, anthraquinone–HRL ( 17 ) selectively photo‐degraded only Man(α1,6)Man, which has a high affinity for HRL, among several mannosides by recognition of both the type and glycosidic linkage profile of the sugar in an oligosaccharide.