Preparation and StructuralCharacterization of RuII‐DMSO and RuIII‐DMSO‐substituted α‐Keggin‐type Phosphotungstates, [PW11O39RuIIDMSO]5– and [PW11O39RuIIIDMSO]4–, and Catalytic Activity for Water Oxidation

Ru^II‐ and Ru^III‐substituted α‐Keggin‐type phosphotungstates with a dimethyl sulfoxide (DMSO) ligand, [PW₁₁O₃₉Ru^IIDMSO]^5– ( 1 ) and [PW₁₁O₃₉Ru^IIIDMSO]^4– ( 2 ), were synthesized. Compound 1 was prepared by reaction of [PW₁₁O₃₉]^7– with [Ru^II(DMSO)₄]Cl₂ in water at 125 °C under hydrothermal conditions and was isolated as a cesium salt. Compound 2 was prepared by reaction of 1 with bromine in water at 60 °C and was isolated as a cesium salt. The compounds were characterized by cyclic voltammetry, elemental analysis, UV/Vis, IR,³¹P NMR, ¹⁸³W NMR, ¹H NMR, and XANES (Ru K‐edge and L₃‐edge)spectroscopic methods. Single crystal structural analysis of 1 revealed that Ru^II is incorporated in the α‐Keggin framework and coordinated by DMSO through a Ru–S bond. Cyclic voltammetry of 1 indicated that the incorporated Ru^II‐DMSO is reversibly oxidizable to the Ru^III‐DMSO derivative 2 . Compound 1 showed catalytic activity for water oxidation in the presence of cerium ammonium nitrate as an oxidant.     

Structural concept of nitroxide as a lipid peroxidation inhibitor

Nitroxides have antioxidative activities toward lipid peroxidation, but the influence of steric factors is not known. We synthesized alkyl-substituted nitroxides at the α-position of the N-O moiety to enhance lipophilicity and the bulk effect. There was good correlation between the IC(50) and lipophilicity (log P(o/w)) of nitroxides with use of the thiobarbituric acid-reactive substances (TBARS) assay. Furthermore, an inhibitory effect on the TBARS assay was dependent upon the number and length of alkyl groups, though nitroxides had almost identical lipophilicity.     

Infrared predissociation spectroscopy of ammonia cluster cations (NH3)n+ (n=2-4) produced by vacuum-ultraviolet photoionization

Infrared predissociation spectroscopy of vacuum ultraviolet-pumped ion (IRPDS-VUV-PI) is performed on ammonia cluster cations (NH3)n+ (n=2-4) that are produced by VUV photoionization in supersonic jets. The structures of (NH3)2+ and (NH3)4+ are determined through the observation of infrared spectra and vibrational calculations based on ab initio calculations at the MP2/6-31G** and 6-31++G** levels. (NH3)2+ is found to be of the "hydrogen-transferred" form having the (H3N+-...NH2) composition. In contrast, (NH3)4+ exhibits the "head-to-head" dimer cation (H3...NH3+ core structure, where the positive charge is shared between two ammonia molecules in the core, and two other molecules are hydrogen bonded onto the core. An unequivocal assignment of the infrared spectrum of (NH3)3+ has not been achieved, because the presence of two isomeric structures could be suggested by the observed spectrum and theoretical calculations.     

An improved phosphoramidite approach for the chemical synthesis of 3′,5′-cyclic diguanylic acid

3′,5′-Cyclic diguanylic acid (c-di-GMP) plays important roles as a signaling and effector molecule in prokaryotes as well as inducing innate and adaptive immune responses in mammalian cells through activation of cell death pathways. An improved phosphoramidite method for the synthesis of c-di-GMP is reported herein. The method is based on the use of an unprecedented 5′-O-formyl ester, which can efficiently and chemoselectively be cleaved from a dinucleotide phosphoramidite intermediate to permit a 1H-tetrazole-mediated cyclocondensation reaction leading to a fully protected c-di-GMP product in a yield of 78%. The native c-di-GMP is isolated in an overall yield of 36% based on the commercial ribonucleoside used as starting material.     

Pulse-resolved measurement of quadrature phase amplitudes of squeezed pulse trains at a repetition rate of 76 MHz

We report pulsed homodyne detection of squeezed pulses at a repetition rate of 76 MHz. Measurement of individual pulses, which were interrogated by the correlation coefficient between adjacent pulses, was realized. A homodyne detector was constructed using a low-noise, high-speed operational amplifier; it had a usable bandwidth of 250 MHz. We observed 2.3 dB of squeezing in both the time and frequency domains.     

Facile synthesis of functionalized 4-aminopyridines

The title compounds are readily available by ring transformation of nitropyrimidione with active methylene compounds in the presence of ammonium acetate.     

Regioselective conjugation of chitosan with a laminin-related peptide, Tyr-Ile-Gly-Ser-Arg, and evaluation of its inhibitory effect on experimental cancer metastasis

A conjugate from the YIGSR peptide and chitosan has been prepared on the basis of a regioselective modification strategy of chitosan, and its antimetastatic activity has been assayed. Chitosan was converted to its organosoluble derivative, 6-O-trityl-chitosan, in 3 steps, and then coupled with the peptide portion containing a spacer amino acid, Ac-Tyr-Ile-Gly-Ser-Arg-beta Ala-OH [beta Ala; beta-alanine]. The product was treated with CHCl2CO2H to afford the desired conjugate, Ac-Tyr-Ile-Gly-Ser-Arg-beta Ala-chitosan, which proved to inhibit the experimental lung metastasis of B16BL6 melanoma cells in mice at lower doses than the parent peptide.     

Reductive displacement of the nitro group into hydrogen in primary α-nitroketones

The nitrogroup in primary α-nitroketones is converted into hydrogen with aluminum chloride and ethanethiol.     

Combined anion-exchange separation and spectrophotometric determination of traces of titanium in sea water

Summary Traces of titanium in sea water have been preconcentrated by anion-exchange from acidified samples in the presence of thiocyanate. Titanium adsorbs strongly on a column of Amberlite CG 400 (SCN^–) and can be stripped easily by elution with 2 M hydrochloric acid — 1.5% hydrogen peroxide solution. Titanium in the effluent is determined spectrophotometrically with diantipyrylmethane as colour reagent. The combined method allows to determine traces of titanium very selectively and sensitively in sea water as well as non-saline water on a 41 sample basis. The method yields a coefficient of variation of 7% at a titanium level of 0.4 g per l.

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Kombinierte Anionenaustauscher-Trennung und spektralphotometrische Bestimmung von Titanspuren in Meerwasser

Zusammenfassung Titanspuren wurden in Gegenwart von Thiocyanat durch Anionenaustausch aus der angesäuerten Probe angereichert. Titan wird an Amberlite CG 400 (SCN^–) stark adsorbiert und kann durch Elution mit 2M HCl — 1,5% H₂O₂ leicht abgelöst werden. Im Eluat wird es spektralphotometrisch mit Diantipyrylmethan bestimmt. Die kombinierte Methode gestattet eine selektive und empfindliche Bestimmung in einer 41-Probe von Meer- oder auch Süßwasser. Für einen Gehalt von 0,4 g Ti/l beträgt der Variationskoeffizient 7%.