| 3571. |
- Taube, Fabian, et al.
(författare)
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Equilibria and dynamics of some aqueous peroxomolybdophosphate catalysts: a potentiometric and 31P NMR spectroscopic study
- 2003
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; , s. 2512-2518
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Tidskriftsartikel (refereegranskat)abstract
- The equilibrium speciation in the pH++qMoO42–+rH2O2+sH2PO4–+tSO42–(H+)p(MoO42–)q(H2O2)r(H2PO4–)s(SO42–)tp–2q–s–2t system in 0.300 M Na2(SO4) medium at 25 °C and [H2O2]tot/[Mo]tot > 2 has been determined from potentiometric data and 31P NMR integral and chemical shift data in the range 1.0 pH 9.0, 2.0 [MoO42–]tot/mM 293, 32 [H2O2]tot/mM 640, 2 [H2PO4–]tot/mM 60 and 200 [SO42–]tot/mM 380. Species with the following compositions were obtained: MoX2P3–(0,1,2,1,0), MoX2P2–(1,1,2,1,0), MoX2P–(2,1,2,1,0), Mo2X4P3–(2,2,4,1,0), Mo2X4P2–(3,2,4,1,0), Mo3X6P3–(4,3,6,1,0), Mo3X6P2–(5,3,6,1,0) and Mo4X8P3–(6,4,8,1,0). The numbers and charges of molybdenum (Mo), peroxide (X), phosphate (P) and sulfate (S) in each species are given in the abbreviated formula MoqXrPsStp–2q–s–2t. The numbers in parentheses refer to the values of p, q, r, s and t in the formula above. The following formation constants with 3 were obtained; log0,1,2,1,0= 5.16 ± 0.09, log1,1,2,1,0= 12.73 ± 0.02 (pKa= 7.63), log2,1,2,1,0= 16.14 ± 0.03 (pKa= 3.42), log2,2,4,1,0= 25.03 (± 0.04), log3,2,4,1,0= 29.54 ± 0.02 (pKa= 4.51), log4,3,6,1,0= 42.30 ± 0.03, log5,3,6,1,0= 44.06 ± 0.08 (pKa= 1.76), log6,4,8,1,0= 57.30 ± 0.07. pKa values for H3PO4 and H2PO4– were determined to 2.00 and 6.48, respectively. Chemical exchange processes were detected by 31P NMR 2D EXSY and selective magnetisation transfer experiments between the complexes. An averaged lifetime, (X2Mo–OP) 30 ms, can be estimated for the MoX2P and Mo2X4P species at pH = 5.5 and 5 °C.
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| 3572. |
- Taube, Magdalena, et al.
(författare)
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Effects of sex steroids on survival and receptor expression in ovarian epithelial tumour cells
- 2003
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Ingår i: International Journal of Oncology. - 1019-6439 .- 1791-2423. ; 22:6, s. 1257-1262
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Tidskriftsartikel (refereegranskat)abstract
- The factors that govern the genesis and progression of ovarian cancer remain unclear. It is thought that ovarian tumours are endocrine related and hormone dependent. We therefore investigated the effects of the sex steroids progesterone, testosterone and 17 beta-estradiol on tumour cell survival and the expression of estrogen receptors (ER) and progesterone receptors (PR) in tumour cells. The study was performed on primary cell cultures derived from patients suffering from epithelial ovarian cancer. The majority of the cells isolated expressed ER and PR to some degree, the combination ER+/PR+ was the most common. Both ER and PR expression decreased after 72-h culture, revealing an unexpectedly dynamic system. The survival rates of cells cultured in progesterone seemed to be inversely related to their PR expression. Lowering levels of 17 beta-estradiol and testosterone in cell cultures reduced cell survival, but it appears that this observation depends on factors other than ER.
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| 3573. |
- Taube, Magdalena, et al.
(författare)
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Low sex steroid environment affects survival and steroid secretion of ovarian tumour cells in primary cultures
- 2002
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Ingår i: International Journal of Oncology. - 1019-6439 .- 1791-2423. ; 20:3, s. 589-594
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Tidskriftsartikel (refereegranskat)abstract
- Ovarian epithelial tumours are considered to be endocrine related. The effects of an environment with low levels of the steroid hormones 17 beta-estradiol, testosterone or progesterone on cell survival and steroid secretion were studied in primary cell cultures derived from 25 patients suffering from epithelial ovarian tumours. Tumour cells cultured in 17 beta-estradiol and testosterone showed a reduced cell survival (-10.3 +/- 2.3% and -15.6 +/- 2.7% minimum survival respectively). This reduction was inversely proportional to hormone concentrations within the range studied. No similar effect was observed in the progesterone cultures. It was found that 17 beta-estradiol was secreted from the primary cell cultures and, interestingly, the amount of 17 beta-estradiol secreted increased with increasing levels of 17 beta-estradiol in the environment. Neither progesterone nor testosterone production was observed in any of the cultures studied. It is believed that 17 beta-estradiol has an antiapoptotic effect on ovarian surface epithelial (OSE) cells. Reduction of 17 beta-estradiol in the environment may inhibit this effect, resulting in reduced cell survival. The ability of ovarian epithelial tumour cells to secrete 17 beta-estradiol suggests that epithelial ovarian tumours play an active role in altering their own hormonal environment, promoting tumour progression.
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| 3574. |
- Tavares, F, et al.
(författare)
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A simple, rapid and non-destructive procedure to extract cell wall-associated proteins from Frankia
- 2000
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Ingår i: Journal of Microbiological Methods. - 0167-7012 .- 1872-8359. ; 39:2, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- A simple cell fractionation procedure was developed to extract cell wall-associated proteins from the nitrogen-fixing actinomycete Frankia. The method was based on washing Frankia mycelia in 62.5 mM Tris-HCl (pH 6.8) buffer supplemented with 0.1% Triton X-100 as solubilizing agent. Cell wall-associated proteins were efficiently extracted in less than 10 min, recovering approximately 94.5+/-7.44 pg protein per extraction procedure from exponentially growing cells, corresponding to 50 ml of culture. The amount of cell lysis occurring during the cell wall extraction was estimated to be 1.50+/-0.51%. Three peptidoglycan hydrolases with apparent molecular masses of 4.7, 12.1, and 17.8 kDa were detected by zymography in the cell wall-associated protein fraction. On the contrary, no cell wall lytic enzyme was detected in the cytoplasmic protein fraction. These results indicate that the present method enables a specific extraction of cell wall-associated proteins. Moreover, fluorescein isothiocyanate (FITC) labelling of the cell surface proteins showed an efficient removal of cell wall-associated proteins. Growth of the treated Frankia cells (i.e. cells from which the cell wall-associated proteins were removed) in semi-solid media suggested that these cells were still viable. This technique is of importance for functionality studies of cell wall-associated proteins, particularly for bacteria where traditional cell fractionation methods are difficult to be applied. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 3575. |
- Tavares, F, et al.
(författare)
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DNase-resistant DNA in the extracellular and cell wall-associated fractions of Frankia strains R43 and CcI3
- 2001
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Ingår i: Current Microbiology. - 0343-8651 .- 1432-0991. ; 42:3, s. 168-172
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Tidskriftsartikel (refereegranskat)abstract
- DNases were shown to be present in the extracellular fraction of Frankia strains R43 and CcI3. In spite of this, DNA was found in both the extracellular and cell wall fractions of these strains, and it was shown that extracellular DNA was resistant to the DNases secreted into the culture medium of both Frankia strains. Furthermore, Southern blot analysis under high stringency conditions revealed the chromosomal origin of the cell wall-adsorbed DNA (CW-DNA). Mobility gel band shift assays suggested that the extracellular DNA and the CW-DNA are engaged in complexes with other molecules, most likely proteins, which are probably responsible for the enzymatic resistance observed against extracellular DNase activities. In addition, it was shown that lysis of a small proportion of the cells in the exponential growth phase may account for the DNA being released into the supernatant and adsorbed to the cell wall.
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| 3576. |
- Tavares, Fernando, et al.
(författare)
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Identification and expression studies of a catalase and a bifunctional catalase-peroxidase in Frankia strain R43
- 2003
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Ingår i: Plant and Soil. - : Kluwer Academic Publishers. - 0032-079X .- 1573-5036. ; 254:1, s. 75-81
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Tidskriftsartikel (refereegranskat)abstract
- A monofunctional catalase and a bifunctional catalase-peroxidase were revealed by activity staining of non-denaturing PAGE in Frankia strain R43. Both enzymes were shown to be cytoplasmatic, growth regulated and expressed mainly during the stationary growth phase. Nevertheless, low levels of constitutive expression could also be detected during the early stages of growth. Immunoblot analyses using a polyclonal antibody raised against a catalase-peroxidase purified from Streptomyces reticuli showed a band of 83.2 kDa, with the same growth dependent pattern as obtained by the non-denaturing PAGE analyses. Induction studies revealed that both enzymes were strongly induced by raising the intracellular concentration of H2O2 with paraquat, but not with exogenous H2O2. In addition, no acquisition of tolerance to exogenous H2O2 was observed whatever the pretreatment of the inocula, i.e. despite the expression level of both hydroperoxidases.
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| 3577. |
- Tay, GK, et al.
(författare)
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PERB11 (MIC) : a polymorphic MHC gene is expressed in skin and single nucleotide polymorphisms are associated with psoriasis.
- 2000
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Ingår i: Clinical and Experimental Immunology. - : John Wiley & Sons. - 0009-9104 .- 1365-2249. ; 119:3, s. 553-558
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Tidskriftsartikel (refereegranskat)abstract
- The susceptibility genes for psoriasis remain to be identified. At least one of these must be in the major histocompatibility complex (MHC) to explain associations with alleles at human leucocyte antigen (HLA)-A, -B, -C, -DR, -DQ and C4. In fact, most of these alleles are components of just two ancestral haplotypes (AHs) designated 13.1 and 57.1. Although relevant MHC gene(s) could be within a region of at least 4 Mb, most studies have favoured the area near HLA-B and -C. This region contains a large number of non-HLA genes, many of which are duplicated and polymorphic. Members of one such gene family, PERB11.1 and PERB11.2, are expressed in the skin and are encoded in the region between tumour necrosis factor and HLA-B. To investigate the relationship of PERB11.1 alleles to psoriasis, sequence based typing was performed on 97 patients classified according to age of onset and family history. The frequency of the PERB11.1*06 allele is 44% in type I psoriasis but only 7% in controls (Pc = 0.003 by Fisher's exact test, two-tailed). The major determinant of this association is a single nucleotide polymorphism (SNP) within intron 4. In normal and affected skin, expression of PERB11 is mainly in the basal layer of the epidermis including ducts and follicles. PERB11 is also present in the upper keratin layers but there is relative deficiency in the intermediate layers. These findings suggest a possible role for PERB11 and other MHC genes in the pathogenesis of psoriasis.
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| 3578. |
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| 3579. |
- Telepnev, Max, et al.
(författare)
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Francisella tularensis inhibits Toll-like receptor-mediated activation of intracellular signaling and secretion of TNF-alpha and IL-1 in murine macrophages
- 2003
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Ingår i: Cellular Microbiology. - : Blackwell Publishing. - 1462-5814 .- 1462-5822. ; 5:1, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- Microbial ligands, including lipopolysaccharide (LPS) and bacterial lipoproteins, activate Toll-like receptors (TLR) of mononuclear phagocytes, thereby inducing proinflammatory cytokines and antimicrobial activity. We show that Francisella tularensis, an intracellular pathogen, is capable of inhibiting this macrophage response. Infection with the live vaccine strain F. tularensis LVS rendered cells of the murine macrophage-like cell line J774A.1 incapable of secreting TNF-alpha or IL-1beta and mobilizing an antimicrobial activity in response to bacterial lipopeptide or Escherichia coli-derived LPS. Inhibition of TNF-alpha secretion occurred also when J774 cells were infected with F. tularensis LVS in the presence of chloramphenicol, but not when they were infected with a mutant of F. tularensis LVS defective in expression of a 23 kDa protein that is upregulated during intracellular infection. Purified F. tularensis LPS did not show an agonistic or antagonistic effect on the E. coli LPS-induced activation of the J774 cells. Francisella tularensis LVS suppressed the capability of the cells to respond to LPS or bacterial lipopeptide (BLP) with activation of nuclear factor kappa B (NF-kappaB), and degradation of the in-hibitor of NF-kappaB, IkappaB, was blocked during the infection. Also the LPS- or BLP-induced phosphorylation of the mitogen-activated protein kinase p38 and the transcription factor c-Jun was inhibited by F. tularensis LVS but not by the 23 kDa protein mutant. In conclusion, F. tularensis appears capable of abrogating the TNF-alpha and IL-1 responses of macrophages induced by E. coli LPS or BLP via a mechanism that involves suppression of several intracellular pathways and is dependent on expression of a bacterial 23 kDa protein.
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| 3580. |
- Tengel, Tobias, et al.
(författare)
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Use of 19F NMR spectroscopy to screen chemical libraries for ligands that bind to proteins
- 2004
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Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 2:5, s. 725-731
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Tidskriftsartikel (refereegranskat)abstract
- Identification of compounds from chemical libraries that bind to macromolecules by use of NMR spectroscopy has gained increasing importance during recent years. A simple methodology based on F-19 NMR spectroscopy for the screening of ligands that bind to proteins, which also provides qualitative information about relative binding strengths and the presence of multiple binding sites, is presented here. A library of fluorinated compounds was assembled and investigated for binding to the two bacterial chaperones PapD and FimC, and also to human serum albumin (HSA). It was found that library members which are bound to a target protein could be identified directly from line broadening and/or induced chemical shifts in a single, one-dimensional F-19 NMR spectrum. The results obtained for binding to PapD using F-19 NMR spectroscopy agreed well with independent studies based on surface plasmon resonance, providing support for the versatility and accuracy of the technique. When the library was titrated to a solution of PapD chemical shift and linewidth changes were observed with increasing ligand concentration, which indicated the presence of several binding sites on PapD and enabled the assessment of relative binding strengths for the different ligands. Screening by F-19 NMR spectroscopy should thus be a valuable addition to existing NMR techniques for evaluation of chemical libraries in bioorganic and medicinal chemistry.
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