Host-guest interactions in the supramolecular incorporation of fullerenes into tailored holes on porphyrin-modified gold nanoparticles in molecular photovoltaics

Novel gold nanoparticles modified with a mixed self-assembled monolayer of porphyrin alkanethiol and short-chain alkanethiol were prepared (first step) to examine the size and shape effects of surface holes (host) on porphyrin-modified gold nanoparticles. The porphyrin-modified gold nanoparticles with a size of about 10 nm incorporated C60 molecules (guest) into the large, bucket-shaped holes, leading to the formation of a supramolecular complex of porphyrin-C60 composites (second step). Large composite clusters with a size of 200-400 nm were grown from the supramolecular complex of porphyrin-C60 composites in mixed solvents (third step) and deposited electrophoretically onto nanostructured SnO2 electrodes (fourth step). Differences in the porphyrin:C60 ratio were found to affect the structures and photoelectrochemical properties of the composite clusters in mixed solvents as well as on the SnO2 electrodes. The photoelectrochemical performance of a photoelectrochemical device consisting of SnO2 electrodes modified with the porphyrin-C60 composites was enhanced relative to a reference system with small, wedged-shaped surface holes on the gold nanoparticle. Time-resolved transient absorption spectroscopy with fluorescence lifetime measurements suggest the occurrence of ultrafast electron transfer from the porphyrin excited singlet states to C60 or the formation of a partial charge-transfer state in the composite clusters of supramolecular complexes formed between porphyrin and C60 leading to efficient photocurrent generation in the system. Elucidation of the relationship between host-guest interactions and photoelectrochemical function in the present system will provide valuable information on the design of molecular devices and machines including molecular photovoltaics.     

Determination of129I and127I in environmental samples by neutron activation analysis (NAA) and inductively coupled plasma mass spectrometry (ICP-MS)

In order to assess the levels and behavior of¹²⁹I (half-life: 1.6×10⁷ y) and¹²⁷I (stable) in the environment, we have developed analytical procedures involving neutron activation analysis (NAA). Environmental samples collected around Tokaimura, Ibaraki Prefecture, Japan, have been analyzed using this method. Ranges of¹²⁹I and¹²⁷I concentrations in surface soil were 0.9–180 mBq kg^–1 and 1–60 mg kg^–1, respectively. Higher¹²⁹I concentrations were found in soil samples collected from coniferous forests, suggesting a contribution from tree canopies in the deposition of this nuclide. Most of the¹²⁹I in soil, was found to be retained in the first 10 cm. The¹²⁹I/¹²⁷I ratios in wheat fields were lower than those in rice paddy fields.A soil sample collected by IAEA from an area contaminated by the Chemobyl accident was also determined. The¹²⁹I concentration and the¹²⁹I/¹²⁷I ratio were 1.6 mBq kg^–1 and 1.7×10^–7, respectively. The¹²⁹I level in this sample was higher than the values obtained in areas far from nuclear facilities in Japan. It was suggested that the analysis of¹²⁹I in soils in the Chernobyl area may be useful in evaluating the¹³¹I levels at the time of the accident.Analyses of¹²⁹I and¹²⁷I by ICP-MS in water samples were also made. The analytical speed of this method was very high, i.e., 3 minutes for a sample. However, there is a sensitivity limitation for¹²⁹I detection due to interference from¹²⁹Xe with the¹²⁹I peak. The detection limits for¹²⁹I and¹²⁷I in water samples were about 0.5 mBq ml^–1 and 0.1 ng ml^–1, respectively.     

Shape-persistent cyclyne-type azamacrocycles: synthesis, unusual light-emitting characteristics, and specific recognition of the Sb(V) ion

Simple members of arene-azaarenecyclynes as a novel family of geometrically-controlled and shape-persistent azamacrocycles have been synthesized. Noteworthy is the specific recognition function for Sb(V). The synthesized azamacrocycles, in particular the Sb(V) complex, have unusually strong light-emitting property.     

Studies on macrolide antibiotics I. Synthesis and antibacterial activity of erythromycin A 9-O-substituted oxime ether derivatives against Mycobacterium avium complex

A series of erythromycin A 9-O-substituted oxime ether derivatives have been synthesized and evaluated for antibacterial activity against Mycobacterium avium complex (MAC) and Staphylococcus aureus. These compounds possessed stronger in vitro activity against MAC including macrolide-resistant strains than clarithromycin (2), although in vitro antibacterial activities of these compounds were less than that of 2 against Staphylococcus aureus. Our studies found that several factors contribute to the antibacterial activity against MAC. The length and spatial orientation of the substituent at 9-position were found to significantly influenced the anti-MAC activity, especially against macrolide-resistant strains. Of all the compounds prepared, erythromycin A 9-[O-(4-phenylbutyl)oxime] (12q) and erythromycin A 9-[O-(3-phenoxypropyl)oxime] (12t) possessed 16 times stronger antibacterial activity than 2 against clarithromycin-resistant strains. Surprisingly, the minimum inhibitory concentrations (MICs) of 12q and 12t against the resistant strains were almost same as those against the susceptible strains. These results suggest that the erythromycin A 9-O-substituted oxime ether derivatives would be promising macrolide antibiotics.     

Palladium-catalyzed oxidation of alcohols via their allyl carbonates under neutral conditions

Treatment of alkyl allyl carbonates derived from various alcohols with a palladium catalyst in MeCN affords ketones and aldehydes in high yields. This new method of oxidation of alcohols can be applied to various alcohols except simple primary alcohols.     

Effectiveness of taurine in protecting biomembrane against oxidant

The effect of taurine in protecting biomembrane attacked by hypochlorous acid (HOCl) was examined using canine erythrocytes which had been pre-treated with HOCl. In the treatment, most of the HOCl was consumed as a result of its reaction with a number of electrophilic substances, such as free amino groups (-NH2) in the membrane, whereas hemoglobin inside the cells was not oxidized. The lysis of HOCl-treated erythrocytes was dependent on the concentration of HOCl and on the incubation time at 37 degrees C. Taurine inhibited the lysis at 37 degrees C in a dose dependent manner. During the incubation of HOCl-treated erythrocytes with taurine, an appreciable amount of monochlorotaurine (TauNHCl) was detected in the supernate. This suggests that taurine might remove the oxidized chlorine from HOCl-treated erythrocytes, resulting in the production of TauNHCl. The effect of taurine on the removal of Cl+ moiety was further examined using Sepharose gel with free amino groups. Taurine removed Cl+ moiety from HOCl-treated Sepharose gel, and the yield of TauNHCl depended on the concentration of taurine and the incubation time. These results indicate that taurine might inhibit the hemolysis by scavenging the oxidized chlorine moiety from the HOCl-treated erythrocytes. Inhibition of the HOCl-induced hemolysis was also observed with other amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)     

Efficient synthesis of 2-modified 1alpha,25-dihydroxy-19-norvitamin D3 with Julia olefination: high potency in induction of differentiation on HL-60 cells

Six novel 2-substituted analogues of 1alpha,25-dihydroxy-19-norvitamin D(3), 6a,b-8a,b, were efficiently synthesized utilizing (-)-quinic acid as the A-ring precursor. The C2-modified A-rings were prepared as 4-alkylated (3R,5R)-3,5-dihydroxycyclohexanones 12-15 from (-)-quinic acid based on radical allylation at the C4 position of methyl (-)-quinicate. The new type of the CD-ring coupling partner 23 was synthesized from 25-hydroxy Grundmann's ketone 19 to apply to the modified Julia olefination to construct a diene unit between the A-ring and the CD-ring. The coupling yields, including a deprotection step, were 47-62%. After the separation of the diastereomers based on C2 stereochemistry, the structure (2alpha or 2beta) was determined by (1)H NMR experiments and compared to DeLuca's 2-methyl- and 2-ethyl-1alpha,25-dihydroxy-19-norvitamin D(3). Thus, the synthesized 2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxy-19-norvitamin D(3) (8a) showed almost the same potency in binding to the bovine thymus vitamin D receptor (VDR) as the natural hormone 1, while its beta-isomer 8b had only a 3% affinity. Both 2alpha-allyl- and 2alpha-propyl-1alpha,25-dihydroxy-19-norvitamin D(3) (6a and 7a) and their 2beta-analogues (6b and 7b) possessed a weak affinity for the VDR. The strong VDR ligand 8a was ca. 36-fold more potent in induction of HL-60 cell differentiation than 1, and interestingly, even the weaker ligand 8b showed a 6.7-fold higher potency in the cell differentiation activity than that of 1.     

Analysis of free fatty acids by a micro-liquid chromatograph directly coupled with a mass spectrometer through a vacuum nebulizing interface

A liquid chromatograph directly coupled with a quadrupole mass spectrometer through a vacuum nebulizing interface was applied to the analysis of various free fatty acids. Chemical ionization mass spectra of the C₇? C₂₂ free fatty acids were first examined using either methanol or benzene as the reagents. Then the practical compositional analysis of the fatty acids were performed with various biological samples such as bean oil, rape oil, palm oil and milk fat where most of the fatty acids are included as their triglycerides.     

Electrodeposition of mercury on gold from very dilute mercury(II) solution

Flameless atomic absorption spectrometry (flameless a.a.s.) was applied to study the state of mercury deposited on a gold plate electrode from very dilute mercury(II) solution by controlled-potential electrolysis. A stable monolayer is formed on the gold electrode by the electrolysis at a potential about 200 mV more positive than the reversible Nernst potential for the reduction of mercury(II) to mercury(0). After the monolayer formation, bulk mercury is deposited on the monolayer at the reversible potential and an adatom layer is also found. The difference of activation free energies between the evaporation of mercury from the monolayer and that from bulk mercury corresponds to the underpotential shift for the electrodeposition of mercury on the gold electrode.     

Solution-phase synthesis of alpha-human atrial natriuretic peptide (alpha-hANP)

Alpha-human atrial natriuretic peptide (alpha-hANP) was synthesized by assembling six peptide fragments in solution followed by deprotection with HF and subsequent air-oxidation. The trimethylbenzyl group was employed as an S-protecting group of cysteine. The HF-dimethylselenide-m-cresol system was employed as a final deprotecting reagent and, at the same time, as a reducing reagent of Met(O). Synthetic alpha-hANP elicited potent diuretic and natriuretic activity in rats.