Charge-transfer interactions,exciplex formations and ionic dissociations in singlet oxygen reactions

Intermolecular perturbation and configuration interaction calculations have been carried out to elucidate the attacking modes of singlet molecular oxygen (¹O₂) to allyl olefins and electron-rich olefins, which are classified into four groups from their molecular structures. It is found: (1) that the attacking modes are dependent on the molecular structure of substrates ; (2) that the charge-transfer (CT) interactions between ¹O₂ and substrates are particularly important for the formation of exciplexes through which the ene and (2+2) reactions of ¹O₂ proceed ; and (3) that the CT energy levels are important in governing the fraction of ionic dissociation to produce Superoxide anion and the relative ratio between the (4+2) and (2+2) reactions of ¹O₂ with dienes, heterocycles and related species.     

Sub-Doppler rotationally resolved spectroscopy of lower vibronic bands of benzene with Zeeman effects

Sub-Doppler high-resolution excitation spectra and the Zeeman effects of the 6(0)(1), 1(0)(1)6(0)(1), and 1(0)(2)6(0)(1) bands of the S1(1)B2u<--S(0)(1)A1g transition of benzene were measured by crossing laser beam perpendicular to a collimated molecular beam. 1593 rotational lines of the 1(0) (1)6(0) (1) band and 928 lines of the 1(0)(2)6(0)(1) band were assigned, and the molecular constants of the excited states were determined. Energy shifts were observed for the S1(1)B2u(v1=1,v6=1,J,Kl=-11) levels, and those were identified as originating from a perpendicular Coriolis interaction. Many energy shifts were observed for the S1(1)B2u(v1=2,v6=1,J,Kl) levels. The Zeeman splitting of a given J level was observed to increase with K and reach the maximum at K=J, which demonstrates that the magnetic moment lies perpendicular to the molecular plane. The Zeeman splittings of the K=J levels were observed to increase linearly with J. From the analysis, the magnetic moment is shown to be originating mostly from mixing of the S1(1)B2u and S2(1)B1u states by the J-L coupling (electronic Coriolis interaction). The number of perturbations was observed to increase as the excess energy increases, and all the perturbing levels were found to be a singlet state from the Zeeman spectra.     

Amphidinolide X,a novel 16-membered macrodiolide from dinoflagellate Amphidinium sp

A novel cytotoxic 16-membered macrodiolide, amphidinolide X (1), has been isolated from a marine dinoflagellate Amphidinium sp. (strain Y-42). The gross structure of 1 was elucidated on the basis of spectroscopic data including one-bond and long-range (13)C-(13)C correlations. The relative and absolute stereochemistries were determined by combined analyses of NOESY data and (1)H-(1)H and (1)H-(13)C coupling constants of 1 and NMR data of the degradation products. Amphidinolide X (1) is the first macrodiolide consisting of polyketide-derived diacid and diol units from natural sources. The biosynthetic origins of 1 were investigated by means of feeding experiments with (13)C-labeled acetates.     

Absorption and fluorescence of a nonionic detergent in aqueous solution

The absorption and fluorescence spectra of a detergent, polyoxyethylene octylphenyl ether, were measured in water at different concentrations. The absorption spectra had a peak at 275 mμ and a shoulder at 281 mμ. The spectra were independent of concentration below the critical micelle concentration, but the molar extinction coefficients of the peak and the shoulder increased with concentration above the critical micelle concentration. The critical micelle concentration value derived from the absorption data was in good agreement with those obtained by other methods. The fluorescence spectra of the detergent in water were independent of concentration in dilute solutions, if the intensities of the spectra were normalized at the peak at 302 mμ. At higher concentrations, a weak excimer band appeared at 345 mμ, whose intensity increased with concentration. The excimer band manifested itself at a concentration slightly lower than the critical micelle concentration. The main band decreased and the excimer band increased, as the temperature was raised. An excimer band was observed in the same region of the spectra for the pure detergent, either in the solid or liquid state. The equilibrium solid spectra exhibited a very strong excimer emission. It was concluded that the excimers were formed within micelles in the case of aqueous solutions.     

Controlled kinetics of non-enzymatic chemiluminescence reactions for simple imaging of DNA and protein

A robust and sensitive non-enzymatic chemiluminescence (CL) imaging method is presented. In the method a fast-emitting CL reaction is tuned to furnish a slower-emitting reaction suitable for simple CL imaging. Typically, non-enzymatic CL reactions between luminol or fluorescein and oxygen species generated by KCN as catalyst, were rather fast and unsuitable for CL imaging; the speed of the reactions could, however, be reduced substantially by changing KCN for CH(3)CN or benzonitrile. Light emission from the tuned CL reaction was intense and long-lived, and even with a simple arrangement high sensitivity could be achieved. The maximum CL peak was reached after approximately 1.5 min in the presence of 25% acetonitrile, and as little as 16 fmol commercial isoluminol-labeled streptavidin was detected and visualized on either microplate or membrane. The approach was further illustrated by imaging of DNA on a membrane and of antibody on a microplate by use of biotin-streptavidin chemistry. Overall, this simple, economical, and sensitive CL imaging system is expected to be very useful in biochemical analysis, and greatly complements currently used enzyme-based CL imaging methods, especially in routine applications.     

Three bits eight states photochromic recording and nondestructive readout by using IR light

A photochromic polymer film containing three different diarylethene derivatives, that is, 1,2-bis(3,5-dimethyl-2-thienyl)perfluorocyclopentene (1), 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene (2), and 1,2-bis(2-methyl-5-phenyl-3-thienyl)perfluorocyclopentene (3) was prepared. Upon UV irradiation, the three derivatives changed to their closed-ring isomers having different colors, yellow, red, and blue. They showed different spectra not only in UV/Vis region but also in the IR spectral region. Upon irradiation with visible light of appropriate wavelengths, each closed-ring isomer was selectively bleached, and three bits eight states recording was performed. The eight states could be read out nondestructively by using IR light of appropriate wavenumbers.     

Adsorption and reactions of NO on clean and CO-precovered Ir(111)

Adsorption and reactions of NO on clean and CO-precovered Ir(111) were investigated by means of X-ray photoelectron spectroscopy (XPS), high-resolution electron energy loss spectroscopy (HR-EELS), infrared reflection absorption spectroscopy (IRAS), and temperature-programmed desorption (TPD). Two NO adsorption states, indicative of fcc-hollow sites and atop sites, were present on the Ir(111) surface at saturation coverage. NO adsorbed on hollow sites dissociated to Na and Oa at temperatures above 283 K. The dissociated Na desorbed to form N2 by recombination of Na at 574 K and by a disproportionation reaction between atop-NO and Na at 471 K. Preadsorbed CO inhibited the adsorption of NO on atop sites, whereas adsorption on hollow sites was not affected by the coexistence of CO. The adsorbed CO reacted with dissociated Oa and desorbed as CO2 at 574 K.     

A novel scheme of heterogeneous polymerization of ethylene

The heterogeneous polymerization of ethylene initiated by radiation in tert-butyl alcohol was studied. The polymerization was carried out in a 100-ml reactor at 25–100°C and pressures of 200–300 kg/cm² in the presence of 50 ml of tert-butyl alcohol containing 7 wt-% water. The amounts of polymerized monomer, the average molecular weight of polymer formed, and the molecular weight distribution of polymer were measured at various stages of reaction and at various temperatures. The molecular weight distribution was found to be very much dependent on the reaction time and temperature. For the polymer formed at 50–60°C in the very early stages of reaction, the molecular weight distribution is unimodal, and in the intermediate stage a shoulder appears at a molecular weight higher than the first peak which increases as the polymerization proceeds; eventually a bimodal curve is formed. The bimodal distribution curves were analyzed to determine the fractions and average molecular weights of the each peak. On the basis of these data for the molecular weight distribution and kinetic behavior, a new scheme for the heterogeneous polymerization is proposed which indicates that the polymerization proceeds via propagating radicals in two different physical states, namely, loose and rigid states.     

Atomic absorption spectrometry of traces of tri- and hexavalent chromium

Summary Atomic absorption spectrometry combined with extraction is described for the determination of tri- and hexavalent chromium. The chromium diethyldithiocarbamate chelate was used for chromium (VI), whereas hydroxyquinolate or thenoyltrifluoroacetonate chelate for chromium(III). The method is rapid and precise.

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Zusammenfassung Extraktion und darauffolgende Messung der Atomarabsorption wurden zur Bestimmung von drei- und sechswertigem Chrom verwendet. Die Chelatverbindung mit Diäthyldithiocarbamat wurde für Chrom(VI), der Chelatkomplex mit Hydroxychinolin oder Thenoyltrifluoraceton für Chrom(III) verwendet. Das Verfahren ist rasch und genau.

     

Analysis of scintigrams using fuzzy theory

Textural features for phantom images were extracted. Texture parameters which represent RI distribution--skew, energy, entropy and angular second moment were used. But, it was difficult to analyse the images using discriminant analysis for textural features, because textural features had statistical noise. Therefore fuzzy reasoning was adapted to analyse the images. Textural features for six kinds of images were showed using membership function. The possibility to the image was evaluated using the value of membership function on each images. Fuzzy reasoning could be done easily using max-min composition formula. The reasoning was found more suitable to analyse the images than discriminant analysis and will be considered useful for analysis of clinical scintigrams.