G‐quadruplexes and i‐motifs are tetraplex structures present in telomeres and the promoter regions of oncogenes. The possibility of producing nanodevices with pH‐sensitive functions has triggered interest in modified oligonucleotides with improved structural properties. We synthesized C‐rich oligonucleotides carrying conformationally restricted (2′S)‐2′‐deoxy‐2′‐C‐methyl‐cytidine units. The effect of this modified nucleoside on the stability of intramolecular i‐motifs from the vertebrate telomere was investigated by UV, CD, and NMR spectroscopy. The replacement of selected positions of the C‐core with C‐modified residues induced the formation of stable intercalated tetraplexes at near‐neutral pH. This study demonstrates the possibility of enhancing the stability of the i‐motif by chemical modification. 相似文献
The aim of this study was to evaluate by scanning electron microscope (SEM) photomicrographs the influence of application of halogen light‐curing for fastening the set reaction of high‐viscosity glass ionomer cements (GIC) by assessing the material/dentin interface. Twelve human primary canines were assigned in four groups (n = 3) according to the GIC (Fuji IX, GC or Maxxion R, FGM) and application of halogen light‐curing (60 sec or control—no external energy). Blocks with approximately 6 mm of height were buildup on previously pre‐treated dentin surface in according to the experimental group. After storage at 37 °C, 100% humidity for 48 h, the specimens were then sectioned in slices with 1‐mm thick. The slices were qualitative analyzed using SEM to evaluate possible structural changes. Two examiners independently evaluated the images in order to observe the spherical hollow spaces of each tooth. The photomicrographs revealed the presence of spherical hollow spaces in all experimental groups. However, in both groups that received halogen light‐curing application, it was possible to observe that the presence of these hollow spaces decreased in size and quantity. It can be concluded that the halogen light‐curing application positively decreases in size and quantity in the presence of spherical hollow spaces in GIC. 相似文献
This study surveyed the presence of bacterial pathogens in eight Swedish sewage treatment plants (STPs), with four different treatment methods, focusing on detection of zoonotic bacteria in raw and treated sludge. Salmonella spp., Listeria monocytogenes, Campylobacter coli and jejuni, Escherichia coli O157 and indicator bacteria were investigated. Samplings were performed from July 2000 to June 2002, resulting in 64 raw sludge samples and 69 treated sludge samples. The samples from raw sludge (67%) and treated sludge (55%) were positive for Salmonella; 49 different serotypes were detected. Restriction enzyme analysis and pulsed field gel electrophoresis of Salmonella serotypes indicated that Salmonella persists in STPs and that there is a continuous supply of new strains. There are differences in treatment methods concerning the reduction of pathogens and indicator bacteria. If spread on arable land, sludge increases the environmental load of pathogens; this increases the risk for spreading diseases to people and animals. 相似文献
Weanling male white rats were fed a diet containing a commercially available breakfast cereal. In 28 days they developed a mild anemia coupled with an increased amount of iron in the liver. In parallel work, this same diet was supplemented in a factorial fashion with casein, iron, copper and zinc. The zinc had no effect. Copper supplementation increased the hemoglobin level. Casein decreased liver iron. The copper and casein, when fed together, produced results approaching normal control levels. Supplementation of the diet with additional iron did not increase the hemoglobin or hematocrit but it did further increase iron storage in the liver. It is suggested that cereal enrichment programs might do well to consider copper and protein rather than focus total attention on additional iron and zinc. 相似文献
Sorption of pollutants is a dominant phase transfer process affecting the fate and transport of metals through the subsurface. The movement of contaminants is retarded by sorption to the stationary subsurface porous media and can seriously hinder remediation efforts. Research has shown that the binding of adsorbed metals becomes more pronounced the longer the contaminant is in the subsurface and the release rates of aged metal contaminants have not received the research attention given to freshly added metals in laboratory studies. Metal release rates are also influenced by the presence of dissolved ligands that compete with mineral soil surfaces by providing binding sites. Dissolved organic matter such as bacterial extracellular polymers are common in natural soil solutions and the metal binding properties of bacterial polymers are well established. Therefore, binding of metals to dissolved biopolymers may result in mobilization of an adsorbed metal. This is important for cases where the metals are assumed to be relatively immobile such as in the case of land applied biosolids. In addition, naturally occurring adherent bacteria commonly produce extracellular polymers and thus may modify the bioavailability of meal contaminants at the point of their attachment. In this study samples from three sites, one a land applied sludge test site, were used to investigate the ability of bacterial extracellular polymers to release metals from soils with long-term exposures. The presence of ?200mg/L bacterial extracellular polymer was found to increase the short-term (less than 350h) release of Cu and Pb by a factor of 2-4-fold. 相似文献
Housing in Scotland. Hector Currie & Alan Murie (Eds). Chartered Institute of Housing. Policy and Practice Series, £15.00 paperback. ISBN 0 901607 91 6.
The Home: Words, Interpretations, Meanings and Environments. D. Benjamin (Ed.). Avebury, Aldershot 1995, £37.00 hardback. ISBN 1 856628 8889.
Rethinking Local Democracy. Desmond King & Gerry Stoker (Eds). Macmillan, London, 1996, 233 pp, £13.95, paperback. ISBN 8039 8864 8.
An Introduction to Social Housing. Paul Reeves. Arnold, London, 1996, 273 pp, £13.99, paperback. ISBN 0 340 661976.
Representing the City: Ethnicity, Capital and Culture in the Twenty‐First Century Metropolis. Anthony D. King (Ed.). Macmillan Press, London, 1996, £13.99, paperback. ISBN 0 333601920.