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101.
Solvated cobalt(II) ions in neat 1,3-propanediamine (tn) and n-propylamine (pa) have been characterized by electronic absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The equilibrium between tetrahedral and octahedral geometry for cobalt(II) ion has been observed in a neat pa solution, but not in neat diamine solutions such as tn and ethylenediamine (en). The thermodynamic parameters and equilibrium constant at 298 K for the geometrical equilibrium in pa were determined to be DeltaH degrees = -36.1 +/- 2.3 kJ mol(-1), DeltaS degrees = -163 +/- 8 J mol(-1) K(-1), and K(298) = 6.0 x 10(-3) M(-2), where K = [Co(pa)(6)(2+)]/{[Co(pa)(4)(2+)][pa](2)}. The equilibrium is caused by the large entropy gain in formation of the tetrahedral cobalt(II) species. The solvent exchange of cobalt(II) ion with octahedral geometry in tn and pa solutions has been studied by the (14)N NMR line-broadening method. The activation parameters and rate constants at 298 K for the solvent exchange reactions are as follows: DeltaH() = 49.3 +/- 0.9 kJ mol(-1), DeltaS() = 25 +/- 3 J mol(-1) K(-1), DeltaV() = 6.6 +/- 0.3 cm(3) mol(-1) at 302.1 K, and k(298) = 2.9 x 10(5) s(-1) for the tn exchange, and DeltaH() = 36.2 +/- 1.2 kJ mol(-1), DeltaS() = 35 +/- 6 J mol(-1) K(-1), and k(298) = 2.0 x 10(8) s(-1) for the pa exchange. By comparison of the activation parameters with those for the en exchange of cobalt(II) ion, it has been confirmed that the kinetic chelate strain effect is attributed to the large activation enthalpy for the bidentate chelate opening and that the enthalpic effect is smaller in the case of the six-membered tn chelate compared with the five-membered en chelate. 相似文献
102.
The Effects of Serum on Cellular Uptake and Phototoxicity of Mono-L-Aspartyl Chlorin e6 (NPe6) In Vitro 总被引:1,自引:0,他引:1
Llyar Sheyhedin Katsuo Aizawa Minako Araake Hideo Kumasaka Tetsuya Okunaka Harubumi Kato 《Photochemistry and photobiology》1998,68(1):110-114
Abstract— Previous reports showed that the photosensitizer mono- l -aspartyl chlorin e6 (NPe6) binds to serum proteins. However, the influence of this binding on the cellular uptake and photodynamic therapy (PDT) phototoxicity of NPe6 is still undefined. In this paper, we studied how serum in medium affected the P388 cellular uptake and PDT phototoxicity of NPe6 in vitro. This was assessed by (1) detection of the red shift (654 nm Q band peak of absorption) induced by protein binding NPe6; (2) detection of intracellular concentration of NPe6 by HPLC and (3) measurements of the cell survival ratio after PDT by MTT assay. The 654 nm Q band peak of NPe6 shifted to 665 nm after binding of NPe6 and serum proteins. The protein-bound NPe6 cannot be uptaken by cells, thus there was no PDT phototoxicity. Nevertheless, phototoxicity recovered when the concentration of NPe6 excessed the serum protein binding ability or there was free serum protein in the medium. These data suggested that the cellular uptake of NPe6 is inhibited by serum components in the medium, and that only free NPe6 is accumulated by P388 cells even during relatively long incubations. The cytotoxicity of PDT mainly depends on the free NPe6 level in the medium. 相似文献
103.
Kimitaka Minami Tomotsugu Ohashi Muneyuki Suzuki Takafumi Aizawa Tadafumi Adschiri Kunio Arai 《Analytical sciences》2006,22(11):1417-1423
The local density around pyridazine was evaluated by examining the UV-vis spectral shift of pyridazine in a high-pressure liquid state and supercritical water from 25 to 450 degrees C and from 20 to 45 MPa. Augmentation of the local density was observed from 380 to 420 degrees C, and showed the maximum at a lower density than the critical density of water. The degree of hydrogen bonding was estimated in consideration of the local density augmentation. The estimated degree of hydrogen bonding under subcritical conditions without any difference between the local density and the bulk density corresponded to the previously reported results with a UV-vis absorbance spectral shift of quinoline and an NMR proton chemical shift. However, the degree of hydrogen bonding near the critical point of water was larger than that in the case that the local density augmentation was not taken into account. At 380 degrees C and 0.2 g cm(-3) of the bulk density there are 30% as many hydrogen bonds as those under the ambient condition, and it was around 1.5-times that without considering local-density augmentation. 相似文献
104.
105.
The phase transition behaviour of two optically isotropic, thermotropic cubic mesogens 1,2-bis-(4-n-undecyloxy- and 4-n-dodecyloxy-benzoyl)hydrazine, BABH(11) and BABH(12), was investigated under hydrostatic pressures up to 300 MPa using a high pressure differential thermal analyser, a wide angle X-ray diffractometer and a polarizing optical microscope equipped with a high pressure optical cell. It is found that for BABH(11) and BABH(12), a smectic C (SmC) phase is induced between the isotropic liquid (I) and the cubic (Cub) phases by applying pressures above 10-12 and 16-17 MPa, respectively. A sea-island texture consisting of bright sand-like sea regions (SmC phase) and areas of dark islands (Cub phase) appears in the mesophase under pressures up to 140 MPa, while the sand-like texture of the SmC phase is formed predominantly on cooling under pressure. These observations indicate the destabilization of the cubic phase with increasing pressure. The phase transition sequence of BABH(11) and BABH(12), Cr-Cub-I at atmospheric pressure, changes to Cr-Cub-SmC-I under intermediate pressures and would change to Cr-SmC-I under elevated pressure. 相似文献
106.
The as-deposited titanium film on silicon wafer was electrochemically treated in potential sweep and potential step modes in 0.1 M H2SO4 solution at 30 °C. Under the anodization conditions of potential sweep and properly modulated cyclic voltammetry (CV), nanoscale grains, step-terrace structure and atomic images were clearly observed on the surface of anodic oxide film on titanium. Under potential step conditions, if the anodization time was short (1 s), no grains could be found on the anodic oxide film surface, even though the potential was high up to 9000 mV. Moreover, whatever potential sweep or potential step mode was performed, sufficient time (low sweep rate means a prolonged anodization time) was needed for the formation of nanoscale grains, atomically flat surface and step-terrace structure on the anodized titanium film. 相似文献
107.
We synthesize Y3Al5O12:Ce3+ (YAG:Ce3+) nanoparticles in the presence of citric acid by glycothermal method. Fourier transform infrared absorption spectroscopy measurement indicates that the intensity of the peak corresponding to carboxyl groups coordinating to the nanoparticles increases with increasing amount of citric acid. At the same time, the primary particle diameter decreases from 10.2 to 4.0 nm. In addition, the internal quantum efficiency of the photoluminescence (PL) due to the 4f-5d transition of Ce3+ increases from 22.0% to 40.1% with increasing amount of citric acid. Two kinds of PL decay lifetimes, 16-26 and 72-112 ns, are detected for YAG:Ce3+ nanoparticles, whereas the micron sized YAG:Ce3+ bulk shows the lifetime of 57 ns. We discuss these phenomena from the aspects of the coordination of citric acid and the incorporation of Ce3+ ions into the nanoparticles. 相似文献
108.
S.?SueharaEmail author T.?Aizawa S.?Hishita A.?Nukui S.?Inoue 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,38(1):111-115
Surface structures in the Te/Ni(111) system are revealed by using reflection high-energy electron diffraction combined with X-ray and ultraviolet photoelectron spectroscopies. At a 0.33 mono-layer (ML)-Te/Ni(111) surface, a reversible structural phase transition is observed with a transition temperature Tc of 380
C. The diffraction pattern from the low temperature phase is accompanied by streaks. The high and low temperature phases are characterized by
and
rectangle, respectively. The mechanism of the phase transition is explained by the order-disorder transition with a rumpled chain model. Both 0.51 ML- and 0.44 ML-Te/Ni(111) surfaces exhibit the complex diffraction patterns accompanied by diffuse streaks. These surface structures are characterized by the
rectangle and
, respectively. All diffuse streaks obtained at the above surfaces are consistently interpreted in the view of the ill-ordered arrangements of the well-ordered
linear chains. It is shown that the
linear structure is the key in the Te/Ni(111) system.Received: 1 December 2003, Published online: 20 April 2004PACS:
61.14.Hg Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED) - 68.65.-k Low-dimensional, mesoscopic, and nanoscale systems: structure and nonelectronic properties - 64.60.Cn Order-disorder transformations; statistical mechanics of model systems 相似文献
109.
The penalty function formulation of the finite element method is described for the analysis of transient incompressible creeping flows. Marker particles are utilized to represent moving free surfaces and to visualize the flow patterns. For determining the movement of markers from element to element, the area coordinate system of the linear triangular element is introduced. With the method presented, a punch indentation problem and an injection problem for an L-shaped cavity are solved for Newtonian and power-law fluids. 相似文献
110.
Masuo Aizawa Aya Morioka Hideaki Matsuoka Shuichi Suzuki Yoichi Nagamura Rikio Shinohara Isao Ishiguro 《Applied biochemistry and biotechnology》1976,1(4):319-328
An enzyme immunosensor has been developed for assaying human immunoglobulin G (IgG). The sensor is composed of an oxygen sensoring system and an antibody-binding membrane. The assay procedure involves the competitive immunochemical reaction of the membrane-bound antibody with nonlabeled and catalase-labeled IgG and the electrochemical determination of membrane-bound catalase activity. The analytical result is directly displayed by the output current of the sensor. The sensor exhibited an excellent performance in monitoring specifically human IgG. 相似文献