Voltammetric study of the ph-behaviour of acetylacetone at the lead dioxide electrode in aqueous solutions

Summary The electrode reaction of acetylacetone (AA) was investigated in unbuffered aqueous solutions by using 3 lead dioxide (PbO₂) indicator electrode. A pH-range of about 2 to 12 was covered. At a pH higher than 3 and lower than 9, the height of the anodic and cathodic peaks is directly proportional to the AA concentration. The PbO₂ electrode seems to be useful for determining a complexing agent such as AA.

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Voltammetrische Untersuchung des pH-Verhaltens Acetylaceton in wäßriger Lösung an der Bleidioxid-Elektrode

Zusammenfassung Die Elektrodenreaktion von Acetylaceton wurde in ungepufferten wäßrigen Lösungen an der PbO₂-Indicatorelektrode untersucht, wobei ein pH-Bereich von 2 bis 12 erfaßt wurde. Bei pH-Werten > 3 und < 9 ist die Höhe der anodischen und kathodischen Peaks direkt proportional der Acetylacetonkonzentration. Die PbO₂-Elektrode scheint für die Bestimmung von Komplexbildnern (wie Acetylaceton) nützlich zu sein.

     

Novel stereoselective entry to 2'-beta-carbon-substituted 2'-deoxy-4'-thionucleosides from 4-thiofuranoid glycals

2'-Beta-methyl- and 2'-beta-hydroxymethyl-2'-deoxy-4'-thionucleosides have been synthesized through PhSeCl-mediated electrophilic glycosidation using 4-thiofuranoid glycals having carbon substituents at the C2-position as a glycosyl donor. Preparation of these glycals were carried out by means of the C2 lithiation of 1-chloro-4-thiofuranoid glycal with LTMP followed by the Birch reduction of the chlorine atom. [reaction: see text]     

Efficient 355-nm generation in CsB3O5 crystal

We demonstrate UV generation in CSB3O5 (CBO) crystals grown by the top-seeded solution growth technique. 355-nm UV light was generated by use of a type II CBO crystal as a sum frequency of the fundamental light and the second harmonic of a nanosecond Nd:YVO4 laser. A 3.0-W output of the third-harmonic was obtained at a repetition rate of 31 kHz. The conversion efficiency from the fundamental light to the third harmonic reached 30%, which was 1.5 times higher than that obtained with a type II LiB3O5 crystal under the same experimental conditions.     

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6相似文献   

Novel fluorescent isoquinoline pigments, panaefluorolines A-C from the cultured mycobiont of a lichen, Amygdalaria panaeola

Novel fluorescent substances, named panaefluorolines A-C (1-3), were isolated from the cultured mycobiont of a lichen, Amygdalaria panaeola. These structures were elucidated on the basis of spectroscopic data, especially 2D NMR.     

Histone core slips along DNA and prefers positioning at the chain end

We studied the stability and dynamics of a model of a nucleosome, the fundamental unit for the packing of long DNA in eukaryotes, using a Brownian dynamics simulation. For the proper folding of a stiff polymer on a core particle, moderate attractive interaction is shown to be essentially important, which explains the empirical experimental protocol for the reconstitution of nucleosomes. The effect of the chain end on the positioning of the core particle is examined and compared with the experimental data by atomic force microscopy measurement. It is also suggested that the core particle exhibits sliding motion along the chain as a manifestation of Brownian motion.     

Phase determination by wavelength-modulated diffraction. I. Centrosymmetric case

Wavelength-modulated diffraction was developed by Iwasaki, Yurugi & Yoshimura [Acta Cryst. (1999), A55, 864-870] as a method for phase determination, in which the intensity of Bragg reflections is recorded using radiation whose wavelength is changing continually over a range in the vicinity of the absorption edge of an atom in the crystal. Using a ferrocene derivative crystal (chemical formula C36H32O7Fe, space group P2(1)/a) with the Fe atoms chosen as anomalous scatterers, measurements were made of the intensity gradient dI/d lambda of the reflections with an imaging plate as a detector on a synchrotron radiation source at Ritsumeikan University. In the case of a centrosymmetric crystal, the phase of the structure factor could be derived by measuring only the sign of dI/d lambda at one wavelength in the range. Of 104 reflections measured, the correct phase was assigned to 101 reflections. A discussion is given on the errors involved and on the limits of application of the method.     

In Vivo EPR Imaging of a Perfluoroalkyl Radical in Mouse Abdomen

Although it is thought that perfluoro-2,4-dimethyl-3-isopropyl-3-pentyl (PFR-2) is a candidate for electron paramagnetic resonance (EPR) imaging agents because of its high stability, no study has been made yet on the EPR imaging of PFR-2. In this study, EPR imaging of a phantom including PFR-2 and mice that had received PFR-2 was performed by an in vivo EPR imaging system operating at an EPR frequency of 700 MHz equipped with a bridged loop-gap resonator (inner diameter, 41 mm; axial length, 10 mm). Because PFR-2 is insoluble in water, it was dissolved in perfluorocarbon. The PFR-2 solution was put in cylindrical sample tubes with various inner diameters, and these sample tubes were placed together in a larger cylindrical sample tube filled with a physiological saline solution, which was used as a phantom. The spatial resolution was estimated to be about 3 mm on the basis of EPR imaging of the phantom. EPR images of mice that had received a PFR-2 injection via the intraperitoneal route indicated that PFR-2 remained in the peritoneal cavity even 2 days after the injection. This finding suggests that it is possible to perform EPR imaging of experimental animals using PFR-2 as an imaging agent which persists in a biological system. Authors' address: Hidekatsu Yokoyama, National Institute of Advanced Industrial Science and Technology, 2266-98 Anagahora, Shimoshidami, Moriyama-ku, Nagoya, Aichi 463-8560, Japan