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171.
The association of nucleoside triphosphate molecules and calcium ions with purified particles of mycobacteriophage I3 has been documented. The content of nucleoside triphosphate has been determined to be 118 molecules per phage particle by equilibrium dialysis against labelled ATP or 148 molecules per phage particle by the direct determination of labelled nucleoside triphosphate. The concentration of bound Ca2+ exhibited a high degree of variation between different batches, which may be due to the nonspecific binding of Ca2+ by the virus particles. However, the tightly bound Ca2+ not removable by dialysis against calciumspecific chelating agent, showed a constant value of 2985 atoms/phage particle.Abbreviations EGTA
Ethylene glycol-bis (IDDLE" BORDER="0">-aminoethylether)-N,N1 tetraacetic acid
- PFU
plaque forming unit
- NTP
nucleoside triphosphate 相似文献
172.
Xian-He Bu He LiuMiao Du Keith Man-Chung WongVivian Wing-Wah Yam 《Inorganica chimica acta》2002,333(1):32-40
The complexes of Cu(I), Cu(II), Ni(II), Zn(II) and Co(II) with a new polypyridyl ligand, 2,3-bis(2-pyridyl)-5,8-dimethoxyquinoxaline (L), have been synthesized and characterized. The crystal structures of these complexes have been elucidated by X-ray diffraction analyses and three types of coordination modes for L were found to exist in them. In the dinuclear complex [Cu(I)L(CH3CN)]2·(ClO4)2 (1), L acts as a tridentate ligand with two Cu(I) centers bridged by two L ligands to form a box-like dimeric structure, in which each Cu(I) ion is penta-coordinated with three nitrogen atoms and a methoxyl oxygen atom of two L ligands, and an acetonitrile. In [Cu(II)L(NO3)2]·CH3CN 2, the Cu(II) center is coordinated to the two nitrogen atoms of the two pyridine rings of L which acts as a bidentate ligand. The structures of [Ni(II)L(NO3)(H2O)2]·2CH3CN·NO3 (3), [Zn(II)L(NO3)2 (H2O)]·2CH3CN (4) and [Co(II)LCl2(H2O)] (5) are similar to each other in which L acts as a tridentate ligand by using its half side, and the metal centers are coordinated to a methoxyl oxygen atom and two bipyridine nitrogen atoms of L in the same side. The formation of infinite quasi-one-dimensional chains (1, 4 and 5) or a quasi-two-dimensional sheet (2) assisted by the intra- or intermolecular face-to-face aryl stacking interactions and hydrogen bonds may have stabilized the crystals of these complexes. Luminescence studies showed that 1 exhibits broad, structureless emissions at 420 nm in the solid state and at 450 nm in frozen alcohol frozen glasses at 77 K. Cyclic voltammetric studies of 1 show the presence of an irreversible metal-centered reduction wave at approximately −0.973 V versus Fc+/0 and a quasi-reversible ligand-centered reduction couple at approximately −1.996 V versus Fc+/0. The solution behaviors of these complexes have been further studied by UV-Vis and ESR techniques. 相似文献
173.
Insulin-like growth factor I receptor is expressed at normal levels in Nijmegen breakage syndrome cells 总被引:1,自引:0,他引:1
Watanabe H Yu D Sasaki T Shibuya H Hosoi Y Asada M Komatsu K Miura M 《Biochemical and biophysical research communications》2002,295(1):62-66
Curcumin (diferuloylmethane) is a major component of food flavoring turmeric (Curcuma longa), and has been reported to be anticarcinogenic and anti-inflammatory. Although curcumin was shown to have antioxidant properties, its exact antioxidant nature has not been fully investigated. In this report we have investigated the possible antioxidant properties of curcumin using EPR spectroscopic techniques. Curcumin was found to inhibit the (1)O(2)-dependent 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) formation in a dose-dependent manner. (1)O(2) was produced in a photosensitizing system using rose bengal as sensitizer, and was detected as TEMP-(1)O(2) adducts by electron paramagnetic resonance (EPR) spectroscopic techniques using TEMP as a spin-trap. Curcumin at 2.75 microM caused 50% inhibition of TEMP-(1)O(2) adduct formation. However, curcumin only marginally inhibited (24% maximum at 80 microM) reduction of ferricytochrome c in a xanthine-xanthine oxidase system demonstrating that it is not an effective superoxide radical scavenger. Additionally, there was minor inhibition of DMPO-OH adduct formation by curcumin (solubilized in ethanol) when an ethanol control was included in the EPR spin-trapping study, suggesting that curcumin may not be an effective hydroxyl radical scavenger. Together these data demonstrate that curcumin is able only to effectively quench singlet oxygen at very low concentration in aqueous systems. 相似文献
174.
Crystal structure analysis of amicyanin and apoamicyanin from Paracoccus denitrificans at 2.0 A and 1.8 A resolution. 下载免费PDF全文
R. Durley L. Chen L. W. Lim F. S. Mathews V. L. Davidson 《Protein science : a publication of the Protein Society》1993,2(5):739-752
The crystal structure of amicyanin, a cupredoxin isolated from Paracoccus denitrificans, has been determined by molecular replacement. The structure has been refined at 2.0 A resolution using energy-restrained least-squares procedures to a crystallographic residual of 15.7%. The copper-free protein, apoamicyanin, has also been refined to 1.8 A resolution with residual 15.5%. The protein is found to have a beta-sandwich topology with nine beta-strands forming two mixed beta-sheets. The secondary structure is very similar to that observed in the other classes of cupredoxins, such as plastocyanin and azurin. Amicyanin has approximately 20 residues at the N-terminus that have no equivalents in the other proteins; a portion of these residues forms the first beta-strand of the structure. The copper atom is located in a pocket between the beta-sheets and is found to have four coordinating ligands: two histidine nitrogens, one cysteine sulfur, and, at a longer distance, one methionine sulfur. The geometry of the copper coordination is very similar to that in the plant plastocyanins. Three of the four copper ligands are located in the loop between beta-strands eight and nine. This loop is shorter than that in the other cupredoxins, having only two residues each between the cysteine and histidine and the histidine and methionine ligands. The amicyanin and apoamicyanin structures are very similar; in particular, there is little difference in the positions of the coordinating ligands with or without copper. One of the copper ligands, a histidine, lies close to the protein surface and is surrounded on that surface by seven hydrophobic residues. This hydrophobic patch is thought to be important as an electron transfer site. 相似文献
175.
176.
Ruan X Xu Q Mao HB Li GF Wei J Gong YD Kuang TY Zhao NM 《Journal of Protein Chemistry》2001,20(3):247-254
Changes in the protein secondary structure and electron transport activity of the Triton X-100-treated photosystem I (PSI) and photosystem II (PSII) complexes after strong illumination treatment were studied using Fourier transform-infrared (FT-IR) spectroscopy and an oxygen electrode. Short periods of photoinhibitory treatment led to obvious decreases in the rates of PSI-mediated electron transport activity and PSII-mediated oxygen evolution in the native or Triton-treated PSI and PSII complexes. In the native PSI and PSII complexes, the protein secondary structures had little changes after the photoinhibitory treatment. However, in both Triton-treated PSI and PSII complexes, short photoinhibition times caused significant loss of INE" BORDER="0">-helical content and increase of IDDLE" BORDER="0">-sheet structure, similar to the conformational changes in samples of Triton-treated PSI and PSII complexes after long periods of dark incubation. Our results demonstrate that strong-light treatment to the Triton-treated PSI and PSII complexes accelerates destruction of the transmembrane structure of proteins in the two photosynthetic membranes. 相似文献
177.
Signal peptidase I overproduction results in increased efficiencies of export and maturation of hybrid secretory proteins in Escherichia coli 总被引:4,自引:0,他引:4
Jan Maarten van Dijl Anne de Jong Hilde Smith Sierd Bron Gerard Venema 《Molecular & general genetics : MGG》1991,227(1):40-48
Summary The effects of 25-fold overproduction ofEscherichia coli signal peptidase I (SPase I) on the processing kinetics of various (hybrid) secretory proteins, comprising fusions between
signal sequence functions selected from theBacillus subtilis chromosome and the mature part of TEM-β-lactamase, were studied inE. coli. One precursor (pre[A2d]-β-lactamase) showed an enhanced processing rate, and consequently, a highly improved release of
the mature enzyme into the periplasm. A minor fraction of a second hybrid precursor (pre[Al3i]-β-lactamase), which was not
processed under standard conditions of SPase I synthesis, was shown to be processed under conditions of SPase I overproduction.
However, this did not result in efficient release of the mature β-lactamase into the periplasm. In contrast, the processing
rates of wild-type pre-β-lactamase and pre(A2)-β-lactamase, already high under standard conditions, were not detectably altered
by SPase I overproduction. These results demonstrate that the availability of SPase I can be a limiting factor in protein
export inE. coli, in particular with respect to (hybrid) precursor proteins showing low (SPase I) processing efficiencies. 相似文献
178.
Copper deficiency in wheat ( Triticum aestivum L. cv. Nazareno Stramppeli) markedly affects photosynthetic activity. Flag leaves of copper-deficient plants showed a 50% reduction of the photosynthetic rate expressed as mg CO2 dm−2 h−1 . The activities of PSI and PSII, determined for isolated chloroplasts, as well as fluorescence measurements on intact leaves of copper-deficient plants, indicated a low activity of photosynthetic electron transport. Ribulose bisphosphate carboxylase/oxygenase (Rubisco) activity was not affected by copper deficiency but copper deficiency affected the chloroplast ultrastructure, especially at the level of grana, where a disorganization of thylakoids is evident. 相似文献
179.
Antibodies against pure discoidin I have been used as a tool to ascertain the role of this lectin in aggregation of Dictyostelium discoideum. Discoidin I is widely expressed over the cell surface of aggregation-competent AX-2 cells, as ascertained by indirect immunofluorescence with specific (antidiscoidin I) antibodies. Univalent antidiscoidin I antibodies (Fab fragments) inhibit the aggregation-specific intercellular adhesion of D discoideum AX-2 cells in an in vitro assay. This inhibition depends on antibody concentration and cell density; a 50% inhibition of cell aggregation was obtained at antidiscoidin I Fab concentration of 4.5 mg/ml and 1 X 10(6) cells/ml. Aggregation and morphogenesis on solid support is also effectively inhibited when AX-2 cells are starved in the presence of antidiscoidin I Fab fragments. The inhibition of morphogenesis is also dose dependent and more effective than in the in vitro assay. No inhibition of aggregation either in the in vitro assay or on morphogenesis on solid support was observed with preimmune Fab fragments at any of the concentrations tested (up to 9.6 mg/ml). 相似文献
180.
“Song Lan” is a source of Chinese drugs such as “Daqingye”, “Banlangen”
or “Qingdai”. We have discovered that the two species, “Song Lan” (Isatis indigotica
Fort.) and woad (I. tinctoria L.), were mistakenly described in the literature due to their
morphological polymorphism. In order to clarify the two species, cytology examination, pollen analysis, electrophoretic analysis of isoenzymes and soluble protein were performed. The
results show that previous non-trichiferous type of woad is a “Song Lan”. As in woad,
“Song Lan” is also morphologically of great variability. The base of canline leaves in this
species may be sagittate or auriculate. We have not found the non-trichiferous type of woad
in our country. It is reported for the first time that the chromosome number for “Song
Lan” is 2n=14.
The content of the indole glucoside in fresh leaves of “Song Lan” is about five timeshigher than in woad. For medicine cultivation of “Song Lan” is favorable. 相似文献