Synthesis of ethynylpyrene-modified 3-deaza-2′-deoxyguanosines as environmentally sensitive fluorescent nucleosides: Target DNA-sequence detection via changes in the fluorescence wavelength

Novel pyrene-labeled environmentally sensitive fluorescent (ESF) nucleosides [^1p3zG (1a) and ^2p3zG (1b)] possessing the 3-deazaguanine skeleton were synthesized. Among them, ^1p3zG (1a) exhibited longer fluorescence emission wavelengths compared with the previously reported naphthalene-modified ESF nucleoside ^3nzG (48–71?nm longer in polar solvents) and showed remarkable solvent-polarity-sensitive fluorescence properties. Oligodeoxynucleotide (ODN) probes containing ^1p3zG (1a) clearly discriminated target DNAs by the change in the emission wavelength and intensity through monitoring the microenvironmental change around the DNA minor groove. Thus, these pyrene-labeled ESF nucleosides can be applied in gene detection and molecular diagnostics, as well as in the structural analysis of nucleic acids.     

Thermal behavior of ammonium dinitramide and amine nitrate mixtures

Journal of Thermal Analysis and Calorimetry - This paper focuses on the thermal behavior of mixtures of ammonium dinitramide (ADN) and amine nitrates. Because some mixtures of ADN and amine nitrate...     

Double-decker phthalocyanine complex: Scanning tunneling microscopy study of film formation and spin properties

We review recent studies of double-decker and triple-decker phthalocyanine (Pc) molecules adsorbed on surfaces in terms of the bonding configuration, electronic structure and spin state.     

Recent advances in instrumentation for absolute emission quantum yield measurements

The fluorescence and phosphorescence quantum yields (Φ) of standard solutions have been re-evaluated based on an absolute method using an integrating sphere equipped with a multichannel spectrometer. We have examined in detail the Φ value of ruthenium(II) tris(2,2′-bipyridine) complex which have been often used as the standards in the determination of quantum yields of transition-metal complexes. This revealed that the Φ values for [Ru(bpy)₃]²⁺ were 0.063 in deaerated H₂O, 0.040 in aerated H₂O, 0.095 in deaerated CH₃CN, and 0.018 in aerated CH₃CN, respectively, which are significantly higher than the previously accepted values.We have also examined the technical aspects in the determination of absolute emission quantum yields for lanthanide complexes and those of organic crystals of anthracene. For the accurate determination for lanthanide complexes, special care must be taken in the spectroscopic measurements because of their narrow absorption and emission bands. For organic crystals, the fluorescence quantum yields are reduced due to reabsorption, chemical impurities and structural defects. Our observations for highly purified anthracene crystals revealed that the lower limit value of Φ was 0.64.     

Enantiocontrolled synthesis of the epoxycyclohexenone moieties of scyphostatin, a potent and specific inhibitor of neutral sphingomyelinase

The epoxycyclohexenone moieties 2 and 3b of scyphostatin (1), a potent and specific inhibitor of neutral sphingomyelinase, were synthesized in enantiomerically pure forms starting from (−)-quinic acid (11). The synthetic method features (i) the preparation of the olefin masked enones 25 and 29, the precursors for the key aldol-type coupling reaction, (ii) the efficient and stereocontrolled aldol-type coupling reactions between 25 (or 29) and benzaldehyde (8) and Garner's aldehyde analogue 9 to deliver alcohols 23 and 24, respectively, both of which possess the requisite asymmetric quaternary carbon center at the C6 position, and (iii) the stereospecific S_N2-type epoxide ring formation of the mesylates 35 and 47 under mild basic conditions to produce the targeted compounds 2 and 3b, respectively.     

Spectroscopic study for photocatalytic decomposition of organic compounds on titanium dioxide containing sulfur under visible light irradiation

Yellowish S-containing TiO2 (S-TiO2) powders were prepared by calcination of a mixture of titanium(III) chloride and ammonium thiocyanate solutions. Three kinds of S-TiO2 were prepared by varying the concentration of ammonium thiocyanate (0.5, 1 or 13 M). X-ray photoelectron spectroscopy spectra of the S-TiO2 showed that sulfur atoms existed on the surface of TiO2 powders. But the peaks assigned to S disappeared after Ar+ etching, which means that these atoms were not doped in the bulk of the TiO2 powders. While UV-visible absorption spectra of S-TiO2 showed that the absorption edges of these photocatalysts were seen to shift to a longer wavelength (lower band gap energy) than those of undoped rutile TiO2 prepared and commercial anatase type TiO2 (ST-01). The S-TiO2 (1 M) exhibited higher photocatalytic activity than ST-01 for degradation of methylene blue in aqueous solution under visible light irradiation (lambda > 400 nm). It was also confirmed by IR spectroscopy that acetaldehyde in oxygen under visible light irradiation (lambda > 400 nm) was decomposed to acetic acid by the S-TiO2 and ST-01 at the first decomposition step.     

Direct observation of reactive trapped holes in TiO2 undergoing photocatalytic oxidation of adsorbed alcohols: evaluation of the reaction rates and yields

To investigate the primary process of photocatalytic oxidation of TiO2, interfacial charge-transfer reaction of trapped holes formed in nanocrystalline TiO2 films by UV irradiation was directly measured by highly sensitive femtosecond and nanosecond transient absorption spectroscopy under low intensity excitation condition to avoid fast electron-hole recombination. Accordingly, the rates and yields of photocatalytic oxidation of several alcohols adsorbed on TiO2 were evaluated successfully.     

Biomimetic synthesis of (+/-)-galanthamine and asymmetric synthesis of (-)-galanthamine using remote asymmetric induction

(+/-)-Galanthamine (1) was synthesized in excellent yield by applying PIFA-mediated oxidative phenol coupling of N-(4-hydroxy)phenethyl-N-(3',4',5'-trialkoxy)benzyl formamide (15b) as a key step. Because of the symmetrical characteristics of the pyrogallol moiety in the substrate (15b), the phenol coupling resulted in a sole coupling product except for volatile components from the oxidizing agent. On the basis of the successful results of the above strategy, (-)-galanthamine (1) was synthesized by employing a novel remote asymmetric induction, where conformation of the seven-membered ring in the product of the phenol coupling was restricted by forming a fused-chiral imidazolidinone ring with D-phenylalanine on the benzylic C-N bond of the tri-O-alkylated gallyl amino moiety. The conformational restriction and successive debenzylation of the protected hydroxyl groups on the pyrogallol ring caused diastereoselective cyclization to yield a cyclic ether having the desired stereochemistry for the synthesis of (-)-1.     

Fe–Si core/Si-shell clusters prepared by double glow discharge sources

Journal of Nanoparticle Research - Using an improved plasma gas condensation cluster deposition system, Fe and Si clusters are prepared by a single glow discharge source and Fe/Si hybrid clusters...