Stability Constants for 1:1 Complexes Formed between2-hydroxypropyl-β-Cyclodextrin with an Average Substitution Degree of 4.4 and Benzene and Alkylbenzenes as Guests by Modified Static Head-Space Gas Chromatography Method

Modified static head-space gas chromatography method (M-SHSGC method) was used to determine the stability constants of benzene and alkylbenzenes with 2-hydroxypropyl-β-cyclodextrin inclusion complexes. The 1:1 stability constants were in agreement with those obtained by conventional SHSGC method. The M-SHSGC method precludes the necessity of the calibration curve by the use of Henry’s law constant of guest. Consequently, it is more advantageous than conventional SHSGC method because the time required to determine the stability constant is markedly reduced.     

A Convenient Synthesis of 4-Homoisotwistane

Tricyclo[5.3.1.0^3,8] undecane (II), which would be conveniently refered to by the trivial name 4-homoisotwistane in accordance with Majerski's nomenclature,¹ was first prepared by Krantz² during the stereoselectivity study on intramolecular Diels-Alder reactions of 5-alkenylcyclohexa-1,3-dienes, and recently discovered independently by Schleyer,³ Majerski¹ and us⁴ to be involved as a reasonably stable intermediate in acid-catalyzed isomerization of various tricycloundecane precursors to equilibrium mixtures of 1 and 2-methyladamantanes.     

Effects of poly(ethylene glycol) (PEG) chain length of PEG-lipid on the permeability of liposomal bilayer membranes

The effects of poly(ethylene glycol) (PEG) chain length of PEG-lipid on the membrane characteristics of liposomes were investigated by differential scanning calorimetry (DSC), freeze-fracture electron microscopy (FFEM), fluorescence polarization measurement and permeability measurement using carboxyfluorescein (CF). PEG-liposomes were prepared from mixtures of dipalmitoyl phosphatidylcholine (DPPC) and distearoyl phosphatidylethanolamines with covalently attached PEG molecular weights of 1000, 2000, 3000 and 5000 (DSPE-PEG). DSC and FFEM results showed that the addition of DSPE-PEG to DPPC in the preparation of liposomes caused the lateral phase separation both in the gel and liquid-crystalline states. The fluidity in the hydrocarbon region of liposomal bilayer membranes was not significantly changed by the addition of DSPE-PEG, while that in the interfacial region was markedly increased. From these results, it was anticipated that the CF leakage from PEG-liposomes is accelerated compared with DPPC liposomes. However, CF leakage from liposomes containing DSPE-PEG with a 0.060 mol fraction was depressed compared with regular liposomes, and the leakage decreased with increasing PEG chain length. Furthermore, the CF leakage from liposomes containing DSPE-PEG with a 0.145 mol fraction was slightly increased compared with that of liposomes containing DSPE-PEG with a 0.060 mol fraction. It is suggested that the solute permeability from the PEG-liposomes was affected by not only properties of the liposomal bilayer membranes such as phase transition temperature, phase separation and membrane fluidity, but also the PEG chain of the liposomal surface.     

Stereospecific Hydroformylation of endo-Dicyclopentadiene in the Presence of Rhodium Complex Catalysts. A Route to endo-Tricyclo[5.2.1.02,6]Dec-8-exo-Ylcarbinol,Precursor of 4-Homoisotwistane

Since the discovery of a potent antiviral activity of 3-amino-4-homoisotwistane (tricyclo [5.3.1.0]undecane, VIII) our efforts have been directed to find out better methods of synthesizing the parent hydrocarbons. In this communication is reported synthesis of a new precursor to 4-homoisotwistane (VIII), endo-tricyclo [5.2.1.0]dec-8-exo-ylcarbinol (IIIx), via hydroformylation of endo-dicyclo-pentadiene (endo-tricyclo [5.2.1.0]deca-3,8-diene) (I) in the presence of rhodium complex catalysts.     

Numerical evaluation of the thermomechanical effective properties of a functionally graded material using the homogenization method

When the stresses of the functionally graded materials (FGMs) are discussed under thermal and/or mechanical loading conditions, the different thermomechanical effective properties are needed. For the steady state thermal analyses, these properties include the Young’s modulus, Poisson’s ratio, thermal expansion coefficient and thermal conductivity. For the transient analyses of the heat conduction problem, on the other hand, the density and heat capacity should be added to the aforementioned properties. The homogenization method (HM) based on the finite element method (FEM) is used as it has advantages, such as it is appropriate for estimating the effective properties of composites with a given periodic fiber distribution and complicated geometries. For a periodic composite structure, it is not necessary to study the whole structure but only a representative volume element (RVE) or a unit cell (UC). As the overall behavior of composites depends on the arrangement of the reinforcements, the corresponding UCs of two different arrangements of the fibers are analyzed; namely the square and hexagonal arrangements. It is found that the square arrangement predicts higher values of the Young’s modulus than the hexagonal one but with small difference. In order to verify the computed values of the properties, the results are compared with previous experimental measurements and results of analytical and numerical methods, and good agreement is achieved.     

Group VIII metal phosphine complexes-catalyzed addition of disilanes to allenic compounds: Formation of new organosilicon compounds containing both vinylsilane and allylsilane units

Addition of chloromethyl- and methoxymethyldisilanes, X₃-_mMe_mSiSiMe_n-X₃-_n (X - Cl and OMe;m, n - 0-2), as well as hexamethyldisilane, to allene and 1, 2-butadiene in the presence of Pd(PPh₃)₄ catalyst gave regioselectively new functionalized organosilicon compounds, 2, 3-bis(organosilyl)prop-1-enes and 2, 3-bis(organosilyl)but-1-enes, respectively. Other group VIII metal-phospine complexes also affected the reaction, but results were found to be less satisfactory. Also, the reaction of any unsymmetrical disilane with an allenic compound gave only a single product; e.g., the addition of chloropentamethyldisilane to 1, 2-butadiene in the presence of Pd(PPh₃)₄ gave CH₂-C(SiMe₃)CH(SiMe₂Cl)Me in 93% yield.     

Determination of Stability Constants for Alkanol/α-Cyclodextrin Inclusion Complexes using the Surface Tension Method

The stability constants for the inclusion of alkanols with-cyclodextrin (-CD) in aqueous solutionhave been determined using the surface tension method. Dataanalyses assuming 1 : 1 stoichiometry were appliedto estimate the stability constants of thesecomplexes. The stability constants obtained using this methodwere in reasonable agreement with the corresponding values inthe literature. Chemically modified -CDs could not beused in this method because those CDs themselves have surfaceactivity. In addition, the relation between the stability constantsand the carbon number of alkanols is discussed.     

A penny-shaped crack in a transversely isotropic piezoelectric layer

In this paper, we develop a model to treat penny-shaped crack configuration in a piezoelectric layer of finite thickness. The piezoelectric layer is subjected to axially symmetric mechanical and electrical loads. Hankel transform technique is used to reduce the problem to the solution of a system of integral equations. A numerical solution for the crack tip fields is obtained for different crack radius and crack position.     

Purification and characterization of exo-type cellouronate lyase

A bacterial strain, Brevundimonas sp. SH203, has an ability to degrade cellouronate, β-(1→4)-linked polyglucuronic acid sodium salt, which is artificially prepared from regenerated cellulose by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation. In a previous paper, an endo-type cellouronate lyase (CUL-I) has been isolated from the strain. In this paper, we purified another cellouronate lyase, CUL-II, from cell-free extracts of Brevundimonas sp. SH203. CUL-II was a monomeric protein with a molecular mass of 56 kDa by size exclusion chromatography and 62 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and most active at pH 7.5. CUL-II formed monomers in a small quantity from cellouronate without forming any intermediate oligomers, whereas it degraded C4′–C5′ unsaturated cellouronate dimer more easily. Thus, CUL-II behaves as an exo-type lyase in degradation of cellouronate. When CUL-I and CUL-II were simultaneously treated to cellouronate, it was degraded to monomers more efficiently than treatment with one enzyme alone, CUL-I or CUL-II. Hence, cellouronate is synergistically degraded to monomers by Brevundimonas sp. SH203 by endo- and exo-type lyases, CUL-I and CUL-II, respectively.     

Calorimetry and cryo-transmission electron microscopic studies of PEG2000-grafted liposomes

The phase behavior of poly(ethylene glycol) grafted liposomes (PEG-liposomes) was investigated by differential scanning calorimetry (DSC), dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM). PEG-liposomes were prepared from mixtures of dipalmitoyl phosphatidylcholine (DPPC) and distearoyl phosphatidylethanolamine with a covalently attached PEG molecular weight of 2000 (DSPE-PEG2000). From the results of DLS measurements, the coexistence of PEG-liposomes and small molecular assemblies were confirmed at mole fractions of DSPE-PEG2000 above about 0.1. Moreover, it was confirmed that small molecular assemblies were disk micelles by cryo-TEM. However, the phase transition enthalpies of PEG-liposomes were hardly changed according to the DSC measurement, though the mole fraction of the PEG lipid increased. From these results, it was suggested that the phase transition enthalpies hardly changed despite mixed micelles being formed because the bilayer structure of the disk micelle maintains high cooperativity between the DPPC molecules.