A novel procedure for the preparation of zinc reagents: a practical synthesis of (+)-biotin

The use of bromine for activation of zinc dust allowed smooth and reproducible reduction of iodide 1 to the corresponding zinc reagent 2. The zinc reagent 2 obtained by the present protocol was allowed to the Fukuyama coupling reaction with thiolactone 3 to provide a key intermediate 4 for (+)-biotin in high yield using a reasonably fair amount of 1 (1.4 equiv).     

Amino acids and peptides. XXXVIII. Facile synthesis of laminin-related peptide-poly(ethylene glycol) hybrids by the solid phase method

Poly(ethylene glycol) (PEG) has been studied as a drug-carrier for proteins, but not for small peptides. Laminin, a cell adhesive protein, has Tyr-Ile-Gly-Ser-Arg (YIGSR) sequence and peptides containing this sequence inhibit experimental metastasis. We have studied PEG hybrids of YIGSR and other small laminin-related peptides. In a previous paper, we reported preparation of YIGSR-PEG hybrids by combination of the solid phase method and the solution method, but the synthetic procedure was problematic. Here we report a facile synthesis of PEG hybrids of YIGSR (PEG-YIGSR, YIGSR-PEG, PEG-YIGSR-PEG) by the solid phase method.     

Doubly-charged scalar bosons from the doublet

We consider the extended Higgs models, in which one of the isospin doublet scalar fields carries the hypercharge Y=3/2. Such a doublet field Φ3/2 is composed of a doubly charged scalar boson as well as a singly charged one. We first discuss a simple model with Φ3/2 (Model I), and study its collider phenomenology at the LHC. We then consider a new model for radiatively generating neutrino masses with a dark matter candidate (Model II), in which Φ3/2 and an extra Y=1/2 doublet as well as vector-like singlet fermions carry the odd quantum number for an unbroken discrete Z₂ symmetry. We also discuss the neutrino mass model (Model III), in which the exact Z₂ parity in Model II is softly broken. It is found that the doubly charged scalar bosons in these models show different phenomenological aspects from those which appear in models with a Y=2 isospin singlet field or a Y=1 triplet one. They could be clearly distinguished at the LHC.     

Calorimetric study of the cubic mesogen, ACBC(6)

The heat capacity of the cubic mesogen ACBC(16) was measured between 16 and 500 K by adiabatic calorimetry. As well as the known condensed phases, a new crystalline phase was found to undergo a glass transition at around 165 K. Phase transitions between crystal, SmC, cubic, and isotropic liquid phases took place at 399.16, 431.15, and 474.30 K, respectively. As in the case of ANBC, a broad hump was observed in the heat capacity of the isotropic liquid phase. The first order nature of the SmC-cubic phase transition was confirmed for the first time by the observation of supercooling of the cubic phase. The broad hump in the isotropic liquid phase was shown to extend to a low temperature side if the isotropic liquid was supercooled, suggesting that the event occurring at the hump is not directly related to the cubic-isotropic liquid phase transition.     

Preconcentration and determination of cadmium by GFAAS after solid-phase extraction with synthetic zeolite.

The solid-phase extraction (SPE) method for the preconcentration of trace amounts of cadmium using synthetic zeolite A-4 and its determination by graphite furnace atomic absorption spectrometry (GFAAS) was investigated. The preconcentration conditions, such as the optimum pH range of the sample solution for the adsorption of cadmium and the kind of acid solution for dissolving the cadmium-adsorbed synthetic zeolite A-4, as well as the measurement conditions for the determination of cadmium by GFAAS, e.g., the ashing and atomizing temperature, were investigated. Quantitative recovery of cadmium onto zeolite A-4 from the sample solution over the pH range 2.0 - 9.0 was achieved by the batch method. After the solid-phase (cadmium-adsorbed zeolite A-4) was separated from the sample solution by a membrane filter, it was dissolved in 2.0 cm(3) of 2.0 mol dm(-3) nitric acid. An aliquot of the resulting solution was injected into the graphite furnace. In GFAAS measurements an alternate gas (Ar, 90%; O(2), 10%) was used as a sheath gas, and the ashing temperature and atomizing temperature were 400 degrees C and 1600 degrees C, respectively. The detection limit (3 sigma) for cadmium was 0.002 microg dm(-3). The relative standard deviation at 0.010 microg dm(-3) was 3.5 - 4.5% (n = 5). The proposed method has been successfully applied to the analysis of trace cadmium in environmental water samples.     

Effect of bredinin on the primary culture of fetal mouse cells and adult mouse lung cells.

The effects of bredinin on the primary culture of fetal mouse cells (fetal cells) and adult mouse lung cells (lung cells) were compared. Bredinin inhibited the growth of both cells, and this inhibition was found to be caused, at least in part, by the inhibition of the S phase and/or the transition from the G1 to S phase of the cell cycle. Bredinin inhibited both DNA and RNA synthesis without affecting protein synthesis. However, the inhibitory effect of bredinin differed between the two cell lines; the fetal cells were more sensitive than the lung cells, and bredinin inhibited DNA synthesis 100 times more potently in the fetal cells. The inhibition of DNA synthesis by bredinin in the fetal cells was gradually lowered by in vitro aging of the fetal cells to a level similar to that in the lung cells. There was no difference in the rate of incorporation of bredinin into the cells between the fetal cells and the lung cells. When fetal tissue was used as an enzyme source, bredinin was converted to bredinin 5'-monophosphate (BMP), but when lung tissue was used, bredinin was not converted. This is in agreement with the finding that bredinin has selective toxicity on fetuses in vivo but is hardly toxic to adult cells, which suggests the involvement of BMP in the selective toxicity of bredinin on the fetus.     

Elucidating a particulate matter deposition episode by combining scanning electron microscopy and X-ray fluorescence spectrometry.

Multielemental composition and morphology of particulate matter samples were examined to detect the presence of two potential responsible pollutant emitters at four sites impacted during a pollution episode in the City of Campana, Argentina. Coke and smoke black are the main constituents associated to the industrial plants that were considered, a priori, as responsible pollutant emitters. Wavelength dispersive X-ray fluorescence (WDXRF) was employed for the analysis of metals in samples coming from both, suspected sources and four sites. On the basis of multielemental composition profiles, a screening analysis was undertaken for exploring similarities among sources and sample sites adopting the average concentration profile of the crustal rock as soil surrogate. Particle morphology was studied by scanning electron microscopy (SEM) in source samples and in those environmental samples selected through the screening analysis. Two types of collected samples were analyzed: 1) those with composition profiles closer to the potential sources and 2) those closer to the cluster rock. This strategy was adequate to identify the responsible source of the contamination episode.     

Solvent-dependent conformational switching of the aromatic N-methyl amides depending upon the acceptor properties of solvents

An aromatic N-methyl amide containing N-(2-pyridyl) and 2,6-pyridinedicarboxamide moieties switches its conformation from cis to trans depending upon the acceptor number of solvents.