Stereoselective synthesis of the both enantiomers of disparlure,the pheromone of the gypsy moth

The both enantiomers of disparlure [(7R, 8S)-(+)-epoxy-2-methyloctadecane and its (7S,8R)-(?)-isomer] were synthesized from (2R, 3R)-(+)-tartaric acid in a stereoselective manner. (+)-Disparlure was found to be biologically active.     

An estimation of the temperature dependence of the excluded-volume integral

Lower critical solution temperatures (LCST) of trans-decalin solutions of polystyrene were measured on a newly built electric thermostat, the theta point Θ_L associated with the LCST being determined as 662 K. By use of this result together with the literature data for the ordinary theta point (Θ_U) and the entropy of dilution parameter, the excluded-volume integral B(T) was estimated in terms of the Eichinger method over the temperature range Θ_U to Θ_L. This enabled us to calculate the excluded-volume variable $\text{z}\text{as}\text{0.770 C}{}_{\mathrm{<mtext>M</mtext>}}\text{′ B(T)}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{0.5}$. Here, C_M′ is a numerical factor specific for a given polymer-solvent system and $\text{M}$_w is the weight-average molecular weight. Using the z values calculated from the above expression, we analysed the data on dilute solution properties of polystyrene reported by Berry and by Inagaki et al. It was found that the Domb-Barrett and the Suzuki equations for α_s (the linear expansion factor for the radius of gyration) were in good agreement with Berry's data of light scattering. The first coefficient k₁ in the series α_ν³ = 1 + k₁z + … (α_ν: the hydrodynamic expansion factor) was experimentally evaluated as 1.70. Furthermore, a conversion of the Suzuki equation for α₅ into that for α_ν with this k₁ value was found to account quite satisfactorily for the viscosity behaviour observed by Inagaki et al.     

Structural characterization of the Ta-rich part of the Ta-Al system

The Ta-rich part of the Ta-Al system has been investigated. On the one hand, the accommodation of the non-stoichiometry in the σ phase has been studied by Rietveld refinement of X-ray powder data obtained from different samples on both sides of the ideal composition (Ta₂Al, P4₂/mnm, tP30). On the other hand, the structure of the β phase has been determined ab initio from powder synchrotron data (analyzed composition Ta_50.7Al_49.3, refined composition Ta_52.6(5)Al_47.4(5) (Ta_45.2(4)Al_40.8(4)), stoichiometric composition Ta₄₈Al₃₈, mP86, P2₁/c, a=9.8707(1) Å, b=9.8766(1) Å, c=16.3539(2), β=116.478(1), R_B=2.6%). This phase is shown to be closely related to the group of the topologically close packed phases. In addition, phase relations have been accurately determined in the Ta-rich end of the system.     

Total synthesis of the proposed structure of `brahol' and the structural revision

Proposed structure of brahol, a natural product, has been disproved by total synthesis of the proposed molecule from myo-inositol. Readily available 1,2;4,5-di-O-isopropylidene-myo-inositol, 3 was converted to 2,5-di-O-acetyl-1,6;3,4-di-O-isopropylidene-allo-inositol by epimerization of the di-triflate of 3. The acetyl group at O-5-position was selectively deprotected by aminolysis or methanolysis enabling the total synthesis of 5-O-methyl-allo-inositol, the proposed structure of brahol in six steps from myo-inositol. A comparison of spectral data of synthetic 5-O-methyl-allo-inositol with that reported for natural brahol revealed that the proposed structure of brahol is incorrect. A detailed structural revision revealed that brahol is nothing but quebrachitol. This study contradicts the first and only report on the natural occurrence of allo-inositol derivative.     

Microcalorimetry study on the microbial activity of permafrost on the Tibetan plateau of China

Microcalorimetric techniques had been used to study the influence of different physicochemical parameters on microbial growth in different permafrosts on the Tibetan plateau. The total heat evolution of the permafrost samples amended with glucose, Q _T , the values of microbial growth rate constant, k, and the heat output power, P _t , were calculated from the power–time (P–t) curves. It is observed that the same coverage vegetation show similar P–t curves, which strongly suggest that the permafrost microorganisms of the homology vegetation coverage have similar structures of community. Furthermore, the vegetation degradation turns out to have significant influence, that is, the better the status of vegetation is, the higher the values of k, CFU and Q _T are.     

Effect of the solvent on the properties of solutions of polysulfone-polyethersulfone blends

The effect of the solvent on the properties of concentrated solutions of polysulfone-polyethersulfone blends, which can be used to produce film and fibrous materials, is studied. It is found that equiconcentrated solutions of polysulfone-polyethersulfone blends, at the same ratio of polymers in N,N-dimethylacetamide and N-methyl-2-pyrrolidone, significantly differ in structure and rheological and optical properties. Solutions in N,N-dimethylacetamide are polydisperse emulsions, while solutions in N-methyl-2-pyrrolidone are systems composed of closely sized interpenetrating fields of polysulfone and polyethersulfone solutions, in which the dispersed phase and the dispersion medium cannot be detected. The turbidity-spectrum method is used to show that, after the introduction of the second (incompatible) polymer, the average size of supramolecular particles significantly increases in N,N-dimethylacetamide and hardly changes in N-methyl-2-pyrrolidone relative to the particle sizes in solutions of the individual polymers. It is determined that these differences results from the different thermodynamic qualities of N,N-dimethylacetamide and N-methyl-2-pyrrolidone with respect to polysulfone.     

Some difficulties in the application of the concept of density of states

The problem of defining N(E), the density of states, for molecular systems is discussed. It is shown that a numeric evaluation of N(E) is often only approximate, even for continuous data, and is not well defined for quantized systems. The application of the concept of density of states is discussed, particularly with regard to the RRKM theory of unimolecular reactions. The sum of states, W(E), and density of states curves are evaluated for several harmonic and anharmonic model systems and the results discussed in order to illustrate the foregoing considerations.     

Study of the Physicochemical and Biological Properties of the Lipid Complex of Marine Microalgae Isolated from the Coastal Areas of the Eastern Water Area of the Baltic Sea

The Baltic Sea algae species composition includes marine euryhaline, freshwater euryhaline, and true brackish water forms. This study aimed to isolate a lipid–pigment complex from microalgae of the Baltic Sea (Kaliningrad region) and investigate its antimicrobial activity against Gram-positive and Gram-negative bacteria. Microalgae were sampled using a box-shaped bottom sampler. Sequencing was used for identification. Spectroscopy and chromatography with mass spectroscopy were used to study the properties of microalgae. Antibiotic activity was determined by the disc diffusion test. Lipids were extracted using the Folch method. Analysis of the results demonstrated the presence of antimicrobial activity of the lipid–pigment complex of microalgae against E. coli (the zone diameter was 17.0 ± 0.47 mm and 17.0 ± 0.21 mm in Chlorella vulgaris and Arthrospira platensis, respectively) and Bacillus pumilus (maximum inhibition diameter 16.0 ± 0.27 mm in C. vulgaris and 16.0 ± 0.22 mm in A. platensis). The cytotoxic and antioxidant activities of the lipid complexes of microalgae C. vulgaris and A. platensis were established and their physicochemical properties and fatty acid composition were studied. The results demonstrated that the lipid–pigment complex under experimental conditions was the most effective against P. pentosaceus among Gram-positive bacteria. Antimicrobial activity is directly related to the concentration of the lipid–pigment complex. The presence of antibacterial activity in microalgae lipid–pigment complexes opens the door to the development of alternative natural preparations for the prevention of microbial contamination of feed. Because of their biological activity, Baltic Sea microalgae can be used as an alternative to banned antibiotics in a variety of fields, including agriculture, medicine, cosmetology, and food preservation.     

Calculation of the rotational magnetic moments of the ammonia and water molecules

We calculate the rotational magnetic moments and the corresponding g-factors for water and ammonia. Our results are g_xx = 0.397, g_yy = 0.769 and _zz = 0.345 for water and g_xx = g_yy = 0.69 and g_zz = 0.51 for ammonia. The experimental values are g_xx = 0.585, g_yy = 0.742 and g_zz = 0.666 for water and g_xx = g_yy = 0.56 and g_zz = 0.484 for ammonia.     

Determination of the absolute configuration of marine oxylipin topsentolide A1 by the synthesis of the enantiomer of the natural product

Two possible stereoisomers of topsentolide A₁, a cytotoxic oxylipin against human solid tumor cell lines, were prepared in order to determine the stereochemistry of natural product. That is, the enantiomer of topsentolide A₁, (8S,11S,12R)-isomer, and its diastereomer was efficiently synthesized in a stereoselective manner. The stereochemistry of topsentolide A₁ was determined to be 8R,11R,12S by comparing NMR spectra and specific rotations of the synthetic isomers and the natural product.     

Computing the distribution of the Robinson-Foulds distance

With the exponential growth of genome databases, the importance of phylogenetics has increased dramatically over the past years. Studying phylogenetic trees enables us not only to understand how genes, genomes, and species evolve, but also helps us predict how they might change in future. One of the crucial aspects of phylogenetics is the comparison of two or more phylogenetic trees. There are different metrics for computing the dissimilarity between a pair of trees. The Robinson-Foulds (RF) distance is one of the widely used metrics on the space of labeled trees. The distribution of the RF distance from a given tree has been studied before, but the fastest known algorithm for computing this distribution is a slow, albeit polynomial-time, O(l⁵) algorithm. In this paper, we modify the dynamic programming algorithm for computing the distribution of this distance for a given tree by leveraging the number-theoretic transform (NTT), and improve the running time from O(l⁵) to O(l³ log l), where l is the number of tips of the tree. In addition to its practical usefulness, our method represents a theoretical novelty, as it is, to our knowledge, one of the rare applications of the number-theoretic transform for solving a computational biology problem.     

Selected Species of the Cucurbitaceae Family Used in Mexico for the Treatment of Diabetes Mellitus

In Mexico, Diabetes mellitus (DM) is a serious health problem, and although the current pharmacological treatments for DM such as insulin and oral hypoglycemics are available, the Mexican population continues to use medicinal plants in the treatment of DM. The antidiabetic properties of the plant species that belong to the Cucurbitaceae family has already been recognized worldwide. Since Mexico is one of the most important centers of diversity of Cucurbitaceae, the present work contributes to the review of the most used species of Cucurbitaceae in the treatment of DM in Mexico. The reviewed species (Cucurbita ficifolia, C. maxima, C. moschata, C. pepo, Ibervillea sonorae, Sechium edule, Citrullus lanatus, Cucumis melo, and C. sativus) revealed that the antidiabetic effects exerted are effective in a number of mechanisms involved in the complex pathogenesis of DM: hypoglycemic, antioxidant, anti-inflammatory, anti-obesity, protective effects on diverse organs and cells, as well as in the control of dyslipidemias; furthermore, the select species of the Cucurbitaceae family could also be essential components of diets for the control of DM in patients with the disease. Thus, the Cucurbitaceae species selected in the present work represent a source of antidiabetic agents that perhaps establish the bases for novel clinical treatments.     

The dependence of the magnitude of the spontaneous polarization on the cell thickness in ferroelectric liquid crystals

The magnitude of the spontaneous polarization (P) was measured for S-3,7-dimethyloctyl 4-n-hexadecyloxybenzoyloxybenzoate, a material with an isotropic to smectic C phase transition (T_c), using a triangular wave method. The temperature dependence of the measured values was well represented by the expression P = P₀(T_c-T)^α· P₀ was found to depend on the cell thickness for thicknesses below 18 μm, but saturated to a constant value above this limit. The value of the exponent α, on the other hand, was found to be insensitive to the cell thickness. The decreased value of the polarization in the thin cells is thought to be a result of polarization screening due to ionic impurities.     

Features of the kinetics of the liquid-phase oxidation of cyclohexanol

The kinetics of oxygen uptake in the cumyl peroxide-initiated oxidation of cyclohexanol (373 K, o-dichlorobenzene) is studied. The parameters of the oxidizability of k _p (2k _t )^?0.5 (which depend on [RH]) and the rate constants of the bi- and trimolecular reactions of chain initiation (k ₀ = 1.25 × 10^?8 L/(mol s) and k′₀ = 2.5 × 10^?9 L²/(mol² s), respectively) are determined by solving the inverse kinetic problem. It is demonstrated that the quadratic-law recombination of peroxyl radicals during cyclohexanol oxidation also occurs without chain termination. The recombination rates of peroxyl radicals with and without chain termination (k′/k _t ) are found to grow with increasing [RH], reaching their maxima at [RH] = 1.0 mol/L, and to diminish subsequently. We conclude that this can be attributed to changes in the ratio between the propagating peroxyl radicals (hydroperoxyl and 1-hydroxycyclohexylperoxyl) in the reaction medium.     

The influence of the supramolecular structure of water on the kinetics of vaporization

The kinetics of water vaporization was studied gravimetrically using a Q-1500 D derivatograph with an accuracy of ±5 × 10^?5 g under atmospheric conditions. Various supramolecular structures were created in liquid water using solutions of K, Na, Ba, and Zn chlorides with various concentrations. The kinetic dependences of weight P loss caused by the vaporization of solutions were compared with the data on pure water used to prepare the solutions. The dependence of the rate of vaporization V on the concentration of hydrated ions in solutions was used to show that the rate V is the sum of the rates of vaporization of particles of two types, (a) H₂O molecules and (b) supramolecular formations (H₂O clusters) with H-bonds. As a consequence, a nonlinear (piecewise linear) dependence of the kinetics of vaporization P = f(τ) of water and solutions is observed. The rate of vaporization (V ₁) along the initial P = f(τ) curve portions is substantially (by ～30%) higher than its stationary value (V).     

Recurrent relations for the approximation of the physicochemical constants of homologues

In addition to the earlier revealed physicochemical constants of homologues whose changes in arbitrary series obey the simplest linear recurrent relations A (n + k) = aA(n) + b, such equations are shown to be applicable to the approximation of the solubility of organic compounds in water (k = 1), temperature dependences of the solubility of organic and inorganic compounds in water (k = ΔT), and nematic-isotropic phase transition temperatures for liquid crystals (k = 2). The a and b coefficients of linear recurrent relations are only determined by the nature of the homologous difference, and, if the homologous difference is the same, they are close for different series. This enables various properties of virtually arbitrary organic compounds to be described by unified recurrent equations, which is equivalent to the existence of a general method for their calculation. For continuous properties (for the example of the temperature dependence of solubility), a method for solving recurrent equations with nonintegral or nonequidistant argument values is suggested.     

Studies on the nongrowth metabolism of the different strains of Tetrahymena cells by isothermal microcalorimetry

The nongrowth metabolic processes of Tetrahymena strains with the different cell densities were monitored by isothermal microcalorimetry, including Tetrahymena thermophila BF₁, Tetrahymena thermophila SB210, Tetrahymena pyriformis GL, the mixed cells of T. thermophila BF₁ and T. thermophila SB210, and the mixed cells of T. thermophila BF₁ and T. pyriformis GL. All the typical power–time curves showed a decreasing trend on the whole. It was found that total heat production (Q _t) and maximum heat output (P _m) decreased significantly with the decrease of cell density. Cell density did not influence significantly the maximum heat output per cell (P _cell) of Tetrahymena cells, which was probably due to enough oxygen. The P _cell and metabolic decrease rate constant (K) values for the mixture of T. thermophila BF₁ and T. pyriformis GL, and that of T. thermophila BF₁ and T. thermophila SB210 were similar to the mean values of P _cell and K for the corresponding single Tetrahymena strain, respectively. It was speculated that the cell mixing did not possibly influence significantly their P _cell and K values because of no competition for nutrition, oxygen, and room, and the low conjunction percentages.     

Synthesis of the ABC-ring models of goniodomin A: preference for the unnatural configuration at C11 of the BC-ring in a non-macrocyclic model system

To confirm the natural relative stereochemistry of the ABC-ring of goniodomin A (1), the corresponding three stereoisomeric compounds, (2R,5S,6S,7S,9S,11R,15S)-, (2R,5S,6S,7R,9R,11S,15R)-, and (2R,5S,6S,7R,9R,11R,15S)-isomers (2, 3, and 5, respectively), were stereoselectively synthesized using a Nozaki-Hiyama-Kishi reaction as a key step. It was also found that a (2R,5S,6S,7R,9R,11S,15S)-isomer (4), corresponding to the absolute configuration of 1 recently proposed by Sasaki, was not detected during the formation of 5 from a common ketodiol substrate under acid-catalyzed spiroacetalization conditions. This would be attributable to the absence of a macrocyclic framework.     

Note on the Hylleraas-Eckart split-shell description of the groundstate of atomic two-electron systems

When the space part of the wavefunction of the groundstate of atomic two-electron systems is taken to be Φ(1, 2)=u(1)v(2)+v(1)u(2), where u=exp(?ar) and v=exp(?br), the parameters a and b as well as the energy associated with Φ(1,2) can be determined in the form of power series involving the nuclear charge Z. For small values of Z the convergence of these series is rather slow. The quantities mentioned, however, may be determined to any degree of accuracy by a method of stepwise approximation.