Nonspecific medium effects versus specific group positioning in the antibody and albumin catalysis of the base-promoted ring-opening reactions of benzisoxazoles

The mechanisms by which solvents, antibodies, and albumins influence the rates of base-catalyzed reactions of benzisoxazoles have been explored theoretically. New experimental data on substituent effects and rates of reactions in several solvents, in an antibody, and in an albumin are reported. Quantum mechanical calculations were carried out for the reactions in water and acetonitrile, and docking of the transition state into a homology model of antibody 34E4 and an X-ray structure of human serum albumin was accomplished. A microenvironment made up of catalytic polar groups (glutamate in antibody 34E4 and lysine in human serum albumin) surrounded by relatively nonpolar groups is present in both catalytic proteins.     

Smectic layer structure of ferroelectric liquid crystal formed between fine polymer fibres

This paper describes the alignment of ferroelectric liquid crystal (FLC) structures formed between aligned polymer fibres, where the FLC smectic layers are determined by polarising microscopy and X-ray diffraction. The FLC/polymer composite films were formed from a nematic phase FLC/monomer solution using a photopolymerisation-induced phase separation method. It was found that bending of the FLC smectic layers was induced in both the film plane and the cross-sectional plane at the phase transition from smectic A to chiral smectic C of the FLC material. The light transmittance properties of the composite film between crossed polarizers was analysed by light propagation simulation in several optical anisotropic media, based on the evaluated smectic layer model.     

Carbonyl reduction with CaH2 and R3SiCl catalyzed by ZnCl2

Ketones and aldehydes were effectively reduced to the corresponding alcohols (or their silyl ethers) by the reaction with CaH₂ and R₃SiCl in the presence of a catalytic amount of ZnCl₂. In the absence of the carbonyl substrate, the reagent reduced R₃SiCl to the corresponding hydrosilane under mild reaction conditions.     

A High Sensitivity Fluorescent Chemo-sensory System Based on β-Cyclodextrin Dimer Modified with Dansyl Moieties

-Cyclodextrin dimer linked with ethylenediamine at the upper rim of the cyclodextrin has been synthesized and then modified with two dansyl moieties inthe presence of N,N'-dicyclohexylcarbodiimide. The sensing ability and bindingproperty of the title compound were investigated for steroids and terpenoids. Thefluorescence intensity of this dimer was decreased when a host–guest complex was formed. The value I/I⁰, where I⁰ and I are fluorescence intensitiesin the absence and presence of a guest and I is I⁰- I, was used as a parameter of sensitivity. This host exhibited a much higher sensitivity and selective molecular recognition ability for bile acids such as ursodeoxycholic acid andchenodeoxycholic acid and terpenoids such as (-)-borneol than the dansyl-modifiedcyclodextrins reported previously including -cyclodextrin dimer. The behaviors of the appended moieties of the host during the formation of host–guest complexes were studied using induced circular dichroism (ICD) and fluorescence spectra. The ICD intensityof this dimer was decreased on accommodation of a guest and this spectral pattern of the title dimer was opposite to that of bis dansyl-modified -cyclodextrin monomer. Theguest-induced variations in the fluorescence and ICD intensities suggest that this dimer formed a 1 : 1 host–guest complex and the appended moieties act as a hydrophobic cap.     

Incorporation of lipid domains in Cerasome, a morphologically-stable organic-inorganic vesicular nanohybrid

To extend the concept of the Cerasome, an organic-inorganic vesicular nanohybrid, this paper investigates the preparation and characterization of a “mixed” Cerasome. The system consists of a Cerasome-forming lipid 1, a cationic synthetic lipid 2, and a zwitterionic phospholipid 3. Lipid mixtures of 1 and 2 or 1 and 3 were used to prepare the mixed Cerasomes. Their lipid distributions were examined using differential scanning calorimetry (DSC), which showed that 1 and 2 (or 1 and 3) were phase-separated in the mixed Cerasomes. These results seem to be mainly attributable to the polymerizable nature of 1. Results of scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX) showed that 1 and 3 were both incorporated into a single Cerasome, not macroscopically separated to form separate vesicles from each lipid component. Mixed Cerasomes of 1 and 2 showed high morphological stability against a membrane-solubilizing surfactant, incorporating up to 70% of 2. On the other hand, the mixed Cerasomes from 1 and 3 were less stable than the mixed Cerasomes from 1 and 2. This relative instability might be attributable to differences between the mixed Cerasomes from 1 and 2 and 1 and 3 in terms of their vesicular sizes, lipid domain sizes, and their relative effectiveness for siloxane network formation. These results strongly support the formation of mixed Cerasomes that have lipid domains in-plane. Systems described in this study are useful to prepare variously mixed Cerasomes that have different surface functionalities and in-plane lipid distribution, but which have high morphological stability.     

Thermal behavior of ternary Sm2Fe17Nx magnets

The Mössbauer spectra of Sm₂Fe₁₇N_x, prepared by the nitrogenation of Sm₂Fe₁₇ powders in an ammonia and hydrogen atmosphere, were observed at elevated temperatures to shed light on the thermal behavior of nitrogen in the compounds Sm₂Fe₁₇N_x. It was found that there were large differences in thermal behavior between the starting Sm₂Fe₁₇, crystalline Sm₂Fe₁₇N_x (x≈1.7) and amorphous Sm₂Fe₁₇N_x(x～7). The thermal decomposition behavior of Sm₂Fe₁₇N_3.2, developed as one of the most promising hard magnetic materials, was found to be different under different atmospheres.     

Structures of new sesquiterpenoids from Farfarae Flos

Two new bisabolane-type sesquiterpenoids, (3R,4R,6S)-3,4-epoxybisabola-7(14),10-dien-2-one and (1R,3R,4R,5S,6S)-1-acetoxy-8-angeloyloxy-3,4-epoxy-5-hydroxybisabola-7(14),10-dien-2-one, and a new oplopane-type sesquiterpenoid, 14(R)-hydroxy-7beta-isovaleroyloxyoplop-8(10)-en-2-one, were isolated from Farfarae Flos along with three known compounds. The structures of these compounds were elucidated on the basis of spectroscopic evidence.     

Reaction potential map analysis of chemical reactivity—III

Reaction potential maps (RPM) have been introduced as a new tool for the study of molecular reactivity. The equipotential energy maps, which are created on given planes around a molecule, define reaction contours towards specific counter-reagent models and are evaluated by perturbation theory. Since the calculated interaction energy involves electrostatic, polarization, exchange, and charge transfer energies, the RPM's can be used to predict site selectivity in a variety of chemical reactions. We found that the calculated RPM's of the SCN^– anion explained well the experimental observations that it reacts at the S atom with soft electrophiles and at the N atom with hard electrophiles. The difference in reactivity between SCN^– and OCN^– was clearly shown by the RPM's of these anions. The ambident nucleophilic nature of the NO ₂ ^– and the CH₂CHO^– anions was also well represented by their RPM's.