Coumarin (C9H6O2) and coumarin derivative, coumarin 6H (C15H15NO2) samples were observed with a polarizing microscope at and around the melting points. The states of the two samples are crystalline at room temperature. When the temperature of the Coumarin sample was raised and a part was melted, the crystalline phases coexisted with the liquid phase. The crystal surface coexisting with the liquid phase went through a repetition of melting and crystallization on slightly modulating the sample temperature. The two-phase coexisting state was observed with a digital camera attached to a microscope. The changes in the number of pixels in the crystal part of the photographed image showed Debye relaxation with temperature change. It was found that the relaxation time was 4.9 s when the number of pixels decreased due to surface melting or increased due to surface crystallization. This relaxation time was in good agreement with that of the dynamic-specific heat measured by AC calorimetry. The coumarin 6H microcrystal also coexisted with the melt in a temperature range at and around the melting point. The change in the number of pixels of the coumarin 6H crystal part showed Debye relaxation with respect to the temperature, and the relaxation time was 15 s, which was the same as the relaxation time of the dynamic-specific heat measured in the melting temperature range of coumarin 6H.
The efficiencies of polyelectrolytes, i.e., polycations and polyanions, and several kinds of water-soluble polymers as fusogens on soybean phospholipid liposome (SL) and egg yolk phospholipid liposome (EL) were investigated by the fluorescence quenching method. There were optimal concentrations for the induction of fusion in every system. Polycations induced fusion of liposomes at very low concentration in comparison with other polymers. Poly(carboxylic acid)s induced fusion at relatively high concentration. A strong acidic polyanion with high molecular weight also induced fusion of liposomes. The induction efficiency of poly(ethylene glycol) on fusion was higher than other nonionic polymers. The efficiency of fusion of EL was lower than that of SL in all systems because of the higher stability of EL membrane. It was found that electrostatic interactions, hydrogen bonding and/or hydrophobic interaction between these water-soluble polymers and liposomal membranes played an important role on aggregation and fusion of liposomes. 相似文献
Polyethylene was prepared by γ-ray-induced polymerization in the temperature range 0–180°C. The morphology and the physical properties of the polymer as polymerized were studied by electron microscopy, differential scanning calorimetry, and gel permeation chromatography. Aggregates of small lamellar crystals with irregularly growing faces were produced below 55°C. Aggregates of large spherical particles were formed above 60°C together with hemispherical particles which adhered to the substrate. A few lamellar crystals of triangular or amoeba-like shapes were also found above 55°C. The polymers formed below 55°C showed a sharp single endothermic DSC peak and a bimodal molecular-weight distribution, while the sample above 60°C had a double endotherm and a unimodal molecular-weight distribution. These facts suggest that the mechanism of crystallization during polymerization below 55°C is different from that above 60°C. The melting point, however, decreased continuously with increasing polymerization temperature and was much lower than that of extended-chain crystals. The results show that the polyethylene, as polymerized, is composed of folded-chain crystals irrespective of the reaction temperature. 相似文献
The small crystal of n-hexatriacontane was observed by a polarizing microscope in the rotator phase transition temperature region. In the temperature region, the rotator phase coexists with the solid phase (low-temperature ordered phase). The boundaries of two phases move reversibly with the temperature change. The area fractional change of the rotator phase can be described by the Debye relaxation. The relaxation time decreases and the relaxation strength increases as the sample temperature is raised. The relaxation time agrees well with that of the dynamic specific heat, which was measured in the frequency range of 0.0003≤f/Hz≤0.05. 相似文献
The solution behavior of hydrophobic-hydrophilic water-soluble graft copolymers consisting of poly[(ethylene-co-vinyl alcohol)-g-ethylene oxide] was investigated by high-resolution NMR spectroscopy and measurements of solution viscosity in tetrahydrofuran, water, and mixtures thereof at various temperatures. A graft copolymer with a backbone containing 2.7 mole% vinyl alcohol exists in an intramolecular phase-separated conformation in aqueous solution, independent of the temperature. Graft copolymers with backbones containing 20.3 mol% vinyl alcohol exhibit an intramolecular mixed-phase conformation in which the mobility of chains in the hydrophobic region depends on temperature. The temperature dependence of the intrinsic viscosity in water shows a maximum near 50°C. 相似文献
A specific inhibitor of DNA cytosine C5-methylases would be useful for studying genomic imprinting, X-chromosome inactivation, carcinogenesis, and regulation of tissue-specific gene expression, for these physiological phenomena appears to be regulated through DNA methylation in promoter sequences. This paper reports a novel convenient in vitro assay method for screening DNA cytosine C5-methylase inhibitor. Our method uses a commercially available Hae III methylase (cytosine C5 methylase), its corresponding Hae III endonuclease, and lambda DNA as their substrate. 相似文献
The reaction of [(cod)M(mu-OMe)]2 (M = Rh, Ir; cod = cycloocta-1,5-diene) with calix[4]arenes (LH4) in the molar ratio of 0.5-0.6:1 gave the rhodium and iridium pi-arene complexes [(cod)M(eta 6-LH3)], while that in the molar ratio of 1.1-1.5:1 (M = Rh) led to the selective formation of the dinuclear complexes [((cod)Rh)2(eta 6:eta 2-LH2)] in which one of the Rh(cod)+ fragments is coordinated by an eta 6-aryl group and the other by two phenolic oxygen atoms; the stepwise synthesis of the Rh-Ir heterobimetallic analogue of the latter complex was further achieved. 相似文献