Metal ion-binding properties of DNA duplexes containing thiopyrimidine base pairs

Thiopyrimidine pairs in DNA duplexes were unexpectedly largely stabilized by complexation with two equivalents of Ag(I) ions and their binding properties were evaluated. The metal ion-binding properties of the thiopyrimidine base pairs differed significantly from those of unpaired bases.     

Application of photoactive yellow protein as a photoresponsive module for controlling hemolytic activity of staphylococcal α-hemolysin

A chimeric protein (N-PYP-Hla), consisting of staphylococcal pore-forming toxin α-hemolysin (Hla) and photoactive yellow protein (PYP), exhibited photoresponsive hemolytic activities, where visible light irradiation gave rise to retardation of hemolysis at 25 °C.     

Photochemical properties of a myoglobin-CdTe quantum dot conjugate

A myoglobin-cadmium telluride quantum dot conjugate was constructed using an artificial heme modified with a thiol moiety as a linker. Irradiation of the myoglobin-cadmium telluride conjugate generated the photoreduced ferrous myoglobin via an electron transfer from the photoexcited quantum dot, leading to the formation of CO-bound myoglobin under a CO atmosphere.     

Practical synthesis of 4,4,4-trifluorocrotonaldehyde: a versatile precursor for the enantioselective formation of trifluoromethylated stereogenic centers via organocatalytic 1,4-additions

The practical synthesis of 4,4,4-trifluorocrotonaldehyde (1) and its application to enantioselective 1,4-additions are described. The organocatalytic 1,4-addition of 1 with several nucleophiles such as heteroaromatics, alkylthiols and aldoximes afforded the corresponding products, each bearing a trifluoromethylated stereogenic center with high optical purity. A resulting product was converted into an MAO-A inhibitor, befloxatone.     

Photoelectrochemical properties of TiO2 photocatalyst and its applications for environmental purification

In view of the situation that environmental issues become more serious day by day, recent studies on practical applications of TiO₂ photocatalysis for environmental purification are reviewed. Although the fundamental aspects and the mechanisms of TiO₂ photocatalysis have recently become quite well understood, effective photocatalytic environmental purifier, especially water purifier, could not be developed to the stage of real industrial technology. The removal rate of gaseous or aqueous contaminants is influenced by numerous parameters; UV light intensity, substrate concentration, O₂ partial pressure, humidity, substrate type, and so on. Moreover, TiO₂ photocatalyst essentially has a difficulty in decomposition of large amount of contaminants or refractory chemicals. As the solutions of these problems, combination with other processes such as advanced oxidation processes and improvement of the design of photocatalytic environmental purification systems are described. During the past several years, the strategies for effective design of the system are well discussed and evaluated. The reactor design for air- or water-purification can be classified into two main strategies: (1) enlargement of reactive surface area and (2) improvement of mass transfer. Based on these insights, very recent achievements for development of photocatalytic environmental purification system with our contribution in each aspect and future research directions are reviewed.     

Preparation of Co–Al and Ni–Al layered double hydroxide thin films by a sol–gel process with hot water treatment

Using hot water treatment of sol–gel derived precursor gel films, Co–Al and Ni–Al layered double hydroxide (LDH) thin films were prepared. The precursor gel films of Al₂O₃–CoO or Al₂O₃–NiO were prepared from cobalt or nickel nitrates and aluminum tri-sec-butoxide using the sol–gel method. Then, the precursor gel films were immersed in a NaOH aqueous solution of 100 °C. Nanocrystallites of Co–Al and Ni–Al LDH were precipitated with the hot water treatment with NaOH solution. The largest amounts of nanocrystals were obtained with a solution of pH = 10 for Co–Al LDH, and with that of pH = 9 for Ni–Al LDH. X-ray diffraction measurements confirmed that this process formed CO₃ ²⁻ intercalated LDHs. Both Co–Al and Ni–Al LDH thin films were confirmed to work as electrodes for electrochemical devices by cyclic voltammogram measurements.     

Tumescenamide C,an antimicrobial cyclic lipodepsipeptide from Streptomyces sp.

Tumescenamide C, a new cyclic lipodepsipeptide, was isolated from a culture broth of an actinomycete Streptomyces sp. KUSC_F05. Tumescenamide C was a congener of tumescenamides A and B, representing a sixteen-membered ring system, consisting of two proteinogenic and three non-proteinogenic amino acids, to which a methyl-branched fatty acid was attached. The planar structure was determined by spectroscopic analysis, while its absolute stereochemistry was determined by chemical degradation and asymmetric synthesis. Tumescenamide C exhibited antimicrobial activity with high selectivity against Streptomyces species.     

Aplyronines D–H from the sea hare Aplysia kurodai: isolation,structures, and cytotoxicity

Five cytotoxic macrolides, aplyronines D–H (4–8), were isolated from the Japanese sea hare Aplysia kurodai. They are new congeners of the antitumor compound aplyronine A (1), which was previously isolated from the same organism. Their structures were determined by spectroscopic analysis (NMR and MS). The cytotoxicity of these new compounds was evaluated in comparison with that of aplyronines A–C (1–3), suggesting the importance of the 7-O-seryl ester group for mediating the potent cytotoxicity of aplyronines.     

Preparation of (Z)-1-fluoro-1-alkenyl carboxylates,carbonates and carbamates through chromium mediated transformation of dibromofluoromethylcarbinyl esters and the reactivity as double acyl group donors

CrCl₂/Mn-mediated transformation of various dibromofluoromethylcarbinyl esters including carboxylates, carbonates and carbamates provided 1-fluoro-1-alkenyl esters via [2,3]-sigmatropic rearrangement of ester group. Reaction proceeded by using CrCl₂/Mn system under mild conditions (in THF at room temperature) to give 1-fluoro-1-alkenyl esters in good yield with an excellent Z selective manner. 1-Fluoro-1-alkenyl ester thus obtained acts as a double acyl donor in the reaction with necleophiles such as amine, thiol, alcohol as well as bifunctional necleophiles such as ethylene diamine derivative.     

Total synthesis and biological evaluation of pacidamycin D and its 3'-hydroxy analogue

Full details of the total synthesis of pacidamycin D (4) and its 3'-hydroxy analogue 32 are described. The chemically labile Z-oxyacyl enamide moiety is the most challenging chemical structure found in uridylpeptide natural products. Key elements of our approach to the synthesis of 4 include the efficient and stereocontrolled construction of the Z-oxyvinyl halides 6 and 7 and their copper-catalyzed cross-coupling with the tetrapeptide carboxamide 5, a thermally unstable compound containing a number of potentially reactive functional groups. This synthetic route also allowed us to easily prepare 3'-hydroxy analogue 32. The assemblage by cross-coupling of the Z-oxyvinyl halide 6 and the carboxamide 5 at a late stage of the synthesis provided ready access to a range of uridylpeptide antibiotics and their analogues, despite their inherent labile nature with potential epimerization, simply by altering the tetrapeptide moiety.