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1.
Ricardo de Souza Pereira Nivaldo AntÔnio Parizotto Vitor Baranauskas 《Applied biochemistry and biotechnology》1996,59(2):135-143
Different strains of baker’s yeast(Saccharomyces cerevisiae) were imaged with an atomic force microscope (AFM). The images of uncoated and nonfixed samples were reproducible with high-constrast
and nanometer-resolution. Molecules from the polysaccharide surface of the cell wall were pictured and the distance of atoms
was measured. The preparation of samples was easy, suggesting that AFM is a useful tool in this type of analyses. 相似文献
2.
In this contribution, the on-line coupling of solid phase extraction (SPE), based on a restricted-access material (RAM), with sequential injection technique (SIA) for the analysis of biological samples, is described. The SIA-RAM system was tested with a new potential antileucotrienic drug (VUFB-19363 (Quinlukast)) for serum analysis. The method is based on SPE with the novel internal-surface reversed-phase column packing material-alkyl-diol silica (ADS). The supports tolerate direct and repetitive injection of proteinaceous fluids (plasma, serum) and allow reversed-phase partitioning at the internal surface. A column packed with a 25 microm C18 alkyl-diol support was used for direct serum injection. Using a 6-port selection valve and the system of three mobile phases, the polar matrix compounds and metabolites are removed by sequentially aspirated mobile phases with lower content of the organic part (methanol-water (2:98) and following acetonitrile-water (20:80)) to the waste, and then, the analyte enriched on the column is eluted by a strong mobile phase (acetonitrile-methanol-water (40:20:40)) to the UV detector without transfer loss. With the fully automated SIA system, a total analysis time of less than 10 min was achieved. The only off-line sample pre-treatment step required to remove particulate matter was centrifugation. The studies showed a range of linearity (2-40 microg ml(-1)) and a high recovery (93.6-96.8%) of drug from the biological matrix with coefficients of variation (RSD) less than 5.0% (n = 6). This paper introduces a new, simple and robust analytical technique suitable for screening determination and direct analysis of drugs in biological materials. 相似文献
3.
Tamura O Shiro T Ogasawara M Toyao A Ishibashi H 《The Journal of organic chemistry》2005,70(12):4569-4577
The 4-hydroxy 4-substituted glutamic acid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols 6 in the presence of MgBr2OEt2 gave cycloadducts 7 in a highly stereoselective manner, whereas noncatalyzed reactions of 5 with acrylates 8 afforded adducts 9. Using the former reaction, syntheses of monatin [(2S,4S)-2], monatin derivative 18, and lycoperdic acid (3) were accomplished. The C4-epimer of monatin [(2S,4R)-2)] was also synthesized by employing the latter cycloaddition. 相似文献
4.
K. Ôhashi 《Analysis Mathematica》1994,20(1):11-25
. [1]. 3 - . 相似文献
5.
Mizuho Nisizawa 《Journal of polymer science. Part A, Polymer chemistry》1969,7(5):1247-1254
When protein is irradiated by γ-rays from a 60Co source in various liquids containing aromatic hydrocarbons, such as benzene, naphthalene, and phenanthrene, the effect of the radiation varies with the irradiation liquids containing aromatic hydrocarbons. An empirical equation for the viscosity change was obtained. Protein irradiated by γ-rays from a 60Co source in air showed the effect of pH on protein reactions. An empirical equation for the viscosity change was obtained. 相似文献
6.
The catalytic oxidation of glucose on Pt electrodes modified by adsorbed metals was studied in 1 M HClO4 by linear sweep voltammetry. The adsorbed metals (denoted as Mad, such as Biad and Pbad) formed on Pt in the potential region more positive than the reversible potential of an M=+/Mo couple, lead to a marked increase in the anodic c?urrent of glucose by about one order of magnitude. The catalytic activity depends on the surface coverage by the Mad. The strongly adsorbed species of lactone type, which are responsible for blocking the successive oxidation, are formed on the electrode surface in the anodic processes of glucose on a bare Pt electrode. The formation of such poisonous species is accelerated in the presence of adsorbed hydrogen on Pt. The effects of Mad were discussed on the basis that Mad plays its major role on the Pt electrode surface in removal of the adsorbed hydrogen which initiates the formation of the poisonous species. 相似文献
7.
The catalytic effects of metal ions on the anodic oxidation of ascorbic acid on a Pt electrode in 1 M HClO4 were studied by linear sweep voltammetry. The anodic peak due to a two-electron oxidation of ascorbic acid shifts to the negative potential side on the addition of Bi3+. This indicates the accelerating effect of Bi3+ on the oxidation of ascorbic acid. The presence of other metal ions, such as Pb2+, Hg2+, Tl+, Ag+ and Sb3+, also exerts similar effects. These metal ions were adsorbed on a Pt electrode at underpotentials and the adsorbed metals (denoted as Mad) still remain on the electrode surface until the electrode potential goes up to and beyond the peak potential of the oxidation of ascorbic acid. On the other hand, metal ions forming no adsorbed layer on Pt, such as Co2+, Zn2+, Fe3+ and Ni2+, exhibit no catalytic effect. These facts suggest that the presence of a Mad on Pt is essential for the promotion of the anodic oxidation of ascorbic acid. However, there is a difference in the catalytic action among the Mad, for example, Cuad, Cdad, Inad, Snad and Moad display no catalytic action.The catalytic activity depends on the degree of surface coverage by the Mad. The maximal effect of the Mad is attained in the submonolayer region. The effects of metal ions were discussed on the basis that the Mad plays its major role in the removal of the adsorbed ascorbic acid occupying active sites on the electrode surface, and provides effective sites for the activation of adjacent water molecules. Furthermore, from the 13C NMR spectra for the oxidation products, the adsorbed water on the Mad appears to function by promoting the subsequent hydration steps, following the electron-transfer step of ascorbic acid. 相似文献
8.
Mizuho Nisizawa 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):925-931
Amino acids, proteins, vitamins, chelating agents, and S-containing compounds were found to protect the shape of the external envelope of the protein molecule from radiation damage. The behavior of the viscosity change closely resembles that found with sodium glutamate and sodium benzoate, as shown by a similar dependence on the concentration. Protein irradiated by γ-rays showed the effect of temperature on changes in the shape of the external envelope of the protein molecule. The behavior of the viscosity change was studied. 相似文献
9.
Mizuho Nisizawa 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):939-944
The radiation protective effect of the breaking of secondary bonding in proteins was examined with 1,2 diamine and 1,2 dihydroxy derivatives such as ethylenediamine, ethylenediaminetetraacetic acid, and propylene glycol, and monosubstituted amines and alcohols such as ethylamine and n-propyl alcohol. An empirical equation for the viscosity change was obtained. 相似文献
10.
A series of 1-(trans-4'-n-alkylcyclohexyl)-2-(4”-halobiphenyl-4'-yl)ethanes, which show nematic phases, was prepared. Their transition temperatures, enthalpies and entropies were measured. Their bulk viscosities, birefringences and dielectric constants were determined by extrapolation. 1-(trans-4'-n-propylcyclohexyl)-2-(4”-fluorobiphenyl-4'-yl)ethane has a high clearing of 125° C, a low viscosity of 25 c.p. at 20 °C, a relatively high birefringence of 0.166 at 25 °C, and a positive dielectric anisotropy of 4.9. The transition temperatures, the N-I transition entropies, the bulk viscosities and the birefringences for the 1-(trans-4'-n-alkylcyclohexyl)-2-(4”-fluorobiphenyl-4'-yl)ethanes exhibited odd-even effects in relation to the number of carbon atoms in the alkyl chain. The bulk viscosity as a function of the third power of the van der Waals radius of the halogeno group, the birefringence as a function of the van der Waals radius of the halogeno group, and the dielectric constants as a function of the dipole moment of the halogeno group are discussed for the 1-(trans-4'-n-propylcyclohexyl)-2-(4”-halobiphenyl-4'-yl)ethanes. 相似文献