Alkynylation of benzotriazole with silylethynyliodonium triflates. Regioselective synthesis of 2-ethynyl-2H-benzotriazole derivatives

Phenyl(trimethylsilylethynyl)iodonium and tert-butyldimethylsilylethynyl(phenyl)iodonium triflates were applied to alkynylation of benzotriazole. Treatment of the silylethynyliodonium triflates with the potassium salt of benzotriazole ion in (t)BuOH and CH(2)Cl(2) gave 2-(trimethylsilylethynyl)-2H-1,2,3-benzotriazole and 2-(tert-butyldimethylsilylethynyl)-2H-1,2,3-benzotriazole in 74% and 76% yields, respectively. The regioisomers, 1-silylethynyl-1H-1,2,3-benzotriazole derivatives, were minor. In both cases of the silyl-substitued ethynyliodonium salts, novel regioselective alkynylation of benzotriazole at the 2 position was observed.     

Thermogravimetry of the products in an imbalance condensation of an aromatic diamine and dichloride

Imbalance condensation of diaminophenylbenzimidazole, DAPBI, with terephthaloyl chloride, TPC was conducted for the purpose of synthesis of macromonomers, expected to be used in syntheses of aromatic polyamides with structural regularities. The products are soluble in dimethylsulfoxide—d6, and their 1H NMR spectra indicate that all the products are carboxyl-terminated. The signal of carboxyphenyl linked to chain ends is different from that of terephthaloyl in the 1H NMR spectra. By use of the ratio of the signal intensity of the former to that of the latter, the number-average degree of polymerization, DP _NMR is determined. With the mole ratio in feed, DP _NMR of the product increases. The TG thermograms of the products are a multistage one. Each stage is classified by temperature and mass loss at an inflection point. Mass loss of each stage classified by temperature at an inflection point corresponds to mass fraction of an aromatic amide with a characteristic degree of polymerization, DP, and that is, the DP distribution of the products is roughly estimated from the TG thermograms. The DP distribution of macromonomers influences performance of aromatic polyamides with structural regularities, derived from the macromonomers. The convenient estimation method of DP distribution by TG is useful in industries of high-performance polymers. To the knowledge, such convenient technique has never reported.     

The dynamic nature of amyloid beta (1-40) aggregation

In this paper, we characterize the dynamic nature of the full amyloid beta (1-40) (Aβ (1-40)) aggregates. We labeled the peptide with either 5-carboxytetramethylrhodamine (TAMRA) or with fluorescein-isothiocyanate (FITC). The labeled peptides were mixed after separate fibrillization, and the dynamic changes in the structure of the fibrils were imaged using confocal microscopy. Fluorescence resonance energy transfer (FRET) measurements showed that the Aβ (1-40) peptides detach from and reattach to the fibrils in a biologically relevant timescale (days). With time, the two peptides mix at the molecular level. This process is concentration dependent and occurs primarily in the external parts of the aggregates with a half time between 4 and 7 days. This study shows that the combination of confocal microscopy and FRET analysis is a facile method for studying dynamic processes in supra-molecular aggregates.     

Rings-on-a-string chain structure in DNA

Using fluorescence microscopy (FM), which permits the observation of single molecules, we found that a pearling structure is generated on a single long DNA molecule upon the addition of a gemini (dimeric) surfactant. This pearling structure was further investigated by performing atomic force microscopy measurements on the same DNA molecules as observed by FM. These observations revealed that the pearling structure is composed of many rings that are interconnected by elongated coil parts along a single DNA molecule, i.e., rings-on-a-string structure. The mechanism of the formation of such an intrachain segregated structure in terms of microphase separation on a single polyelectrolyte chain is discussed.     

The depth of molecular recognition: voltage-sensitive blockage of synthetic multifunctional pores with refined architecture

Voltage-sensitive blockage by ADP, ATP and phytate (IP6) demonstrates that active-site contraction toward the middle of newly synthesized rigid-rod beta-barrels provides a general strategy to rationally create and modulate the voltage sensitivity (and to increase the efficiency) of molecular recognition by synthetic multifunctional pores.     

Review of particle properties

This review of the properties of leptons, mesons, and baryons is an updating of Review of Particle Properties, Particle Data Group [Rev. Mod. Phys. 45, No. 2, Part II, Supplement (1973)]. Data are evaluated, listed, averaged, and summarized in tables.     

Selective extraction and purification of endohedral metallofullerene from carbon soot

A preferential extraction of endohedral metallofullerenes (EMFs) from carbon soot through the use of reduction in the extraction process and a convenient isolation of endohedral metallofullerene anions (EMFs(-)) and empty fullerenes utilizing their difference in solubility are accomplished. EMFs are easily isolated by one-stage high-performance liquid chromatography after chemical oxidation of the extracted endohedral EMFs(-).