An application of activation analysis of aluminum in biological materials

The behavior of aluminum compounds in animals was made clear by using non-destructive neutron activation analysis instead of radiotracer method. Basic aluminum sucrose sulfate (BASS) and dried aluminum hydroxide gel (DAHG) were orally administered to rats. The residual BASS and DAHG on gastric walls of rats were determined by neutron activation analysis. It was obtained the following results that BASS was found at the longer time in the stomach. For reason, it is seemed that BASS is hydrolyzed in gastric juice. And it could not find the aluminum in liver, kidney and spleen.     

Chemical studies on nitrogen heterocyclic skeleton of the Daphniphyllum alkaloids

From a biogenetic point of view, a great variety of related alkaloids isolated from the plant Daphniphyllaceae are related to one another by bond formation or fission. Thus, daphnialcohol acetate (6), a derivative of the degradation products of daphniphylline (1), was subjected to von Braun degradation followed by acid-catalyzed recyclization to give an isomer (8) of daphnialcohol, which has a new type of nitrogen heterocyclic skeleton. Furthermore, daphnilactone-B (3) was converted into a daphniphylline-type compound (19) via a plausible intermediate (21).     

Polymers for DNA delivery

Nucleic acid delivery has many applications in basic science, biotechnology, agriculture, and medicine. One of the main applications is DNA or RNA delivery for gene therapy purposes. Gene therapy, an approach for treatment or prevention of diseases associated with defective gene expression, involves the insertion of a therapeutic gene into cells, followed by expression and production of the required proteins. This approach enables replacement of damaged genes or expression inhibition of undesired genes. Following two decades of research, there are two major methods for delivery of genes. The first method, considered the dominant approach, utilizes viral vectors and is generally an efficient tool of transfection. Attempts, however, to resolve drawbacks related with viral vectors (e.g., high risk of mutagenicity, immunogenicity, low production yield, limited gene size, etc.), led to the development of an alternative method, which makes use of non-viral vectors. This review describes non-viral gene delivery vectors, termed "self-assembled" systems, and are based on cationic molecules, which form spontaneous complexes with negatively charged nucleic acids. It introduces the most important cationic polymers used for gene delivery. A transition from in vitro to in vivo gene delivery is also presented, with an emphasis on the obstacles to achieve successful transfection in vivo.     

Protonation et hydrolyse d'enamine. Epimerisation des immoniums intermediaires

At pH 5 (AcOHAcONa) protonation of the enamine of 3,6,6-trimethylnorpinane 2-one (3-methylnopinone) yields the cis immonium ion 6 (X  OAc), which isomerizes to the thermodynamically more stable trans immonium ion 6′ (X  OAc). Under more strongly acid conditions (aqueous hydrochloric or perchloric acids), the enamonium salts 7 (X  Cl or ClO₄) are formed; these isomerize, with a rate increasing with decreasing acidity to the cis immonium salts 6, stable under these conditions. Epimerization of the cis salt 6 (X  Cl), occurs in ethereal hydrogen chloride, the rate increasing also with decreasing acidity. At pH 5, hydrolysis of the enamine yields 3-methylnopinone, the proportion of the less thermodynamically stable trans isomer increasing with a rise in reaction temperature.     

Silicon clusters: chemistry and structure

The chemical reactions of size selected silicon cluster ions (containing up to 70 atoms) have been studied with a number of different reagents using injected ion drift tube techniques. Both kinetic and equilibrium measurements have been performed as a function of temperature, and the influence of cluster annealing on chemical reactivity explored. Unlike metal clusters, where bulk behavior appears to be approached with around 30 atoms, large silicon clusters (n up to 70) are much less reactive than bulk silicon surfaces. These results suggest that the clusters in the size range examined here are not small crystals of bulk silicon, but have compact, high coordination number structures with few dangling bonds.     

Facile chemoselective synthesis of dehydroalanine-containing peptides

Useful methodology is described for the synthesis of dehydroalanine residues (II) within peptides. The unnatural amino acid (Se)-phenylselenocysteine (I) can be incorporated into growing peptide chains via standard peptide synthesis procedures. Subsequent oxidative elimination affords a dehydroalanine at the desired position. The oxidation conditions are mild and tolerate functionalities commonly found in peptides, including variously protected cysteine residues. To illustrate its utility, cyclic lanthionines have been synthesized by this method.     

Molar volumes and ion pairing of lithium halides in alcohols

The concentration dependence of the apparent molar volumes of lithium halides (and electrolytes in general) in alcohols (and solvents permitting association in general) is, in the first instance, due to changes in the degree of association and to the inherent difference between the apparent molar volumes of the ions and of the ion pairs. Previous publications on the molar volumes of electrolytes in organic solvents, disregarding altogether ion pairing, appear to be incorrect. Data from the literature for lithium chloride and lithium bromide in normal primary alcohols and several branched alcohols from C₁ to C₈ and data from our laboratory for lithium halides in 1-hexanol and 2-ethyl-1-hexanol served for the determination of φ _V and φ _E . Electrical and structural contributions to the values of these functions for the ions and for the ion pairs are discussed.     

NMR studies on the stereospecific polymerization of methyl vinyl ether. Part I. Polymerization by metal halides: Penultimate effect

Methyl vinyl ether (MVE) was polymerized under various conditions by BF₃·O(C₂H₅)₂ and SnCl₄·CCl₃CO₂H catalysts. The effect of polymerization conditions on the steric structure of poly(methyl vinyl ether) (PMVE) was studied by NMR spectra. It was found that the triad isotacticity of PMVE decreased and the syndiotacticity and heterotacticity increased with increasing polarity of the solvent and increasing polymerization temperature. This result coincided with the qualitative conclusion estimated from softening point and infrared spectra. However, the variation of tacticity by the change of the polarity of a solvent was not so large as expected. There was no large difference between the behavior of BF₃·O(C₂H₅)₂ and SnCl₄·CCl₃CO₂H as catalysts. From the relation between the difference of free energy of monomer addition due to the steric structure of the polymer and the polymerization temperature, it was concluded that the penultimate effect really existed and was due to only the difference in enthalpy in the MVE–BF₃. O(C₂H₅)₂ or MVE–SnCl₄·CCl₃CO₂H systems. The penultimate effect was not greatly changed by the polymerization conditions in these systems.     

Birefringence induite dans les directions remarquables d'une suspension de particules rigides en ecoulement

A theoretical formula is derived for the flow birefringence exhibited along the streamlines and in the direction of the shear rate (G) by dilute suspensions of rigid spheroid-like macromolecules; numerical values are computed up to σ = G/D = 900 (D = rotary diffusion coefficient). These results provide two tests for identifying prolate and oblate particles; when combined with the data for observation perpendicular to the plane of flow, they confirm the connection between non-Newtonian viscosity and the Maxwell effect for monodisperse samples; for vanishing rate of shear, they allow a mixture of particles to be characterized by means of a mean rotary diffusion constant ($\text{D}$) and a mean shape coefficient ($\text{R}$).