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991.
Osamu Nureki Patrick O’Donoghue Nobuhisa Watanabe Atsuhiko Ohmori Hiroyuki Oshikane Yuhei Araiso Kelly Sheppard Dieter S?ll Ryuichiro Ishitani 《Nucleic acids research》2010,38(20):7286-7297
The molecular basis of the genetic code relies on the specific ligation of amino acids to their cognate tRNA molecules. However, two pathways exist for the formation of Gln-tRNAGln. The evolutionarily older indirect route utilizes a non-discriminating glutamyl-tRNA synthetase (ND-GluRS) that can form both Glu-tRNAGlu and Glu-tRNAGln. The Glu-tRNAGln is then converted to Gln-tRNAGln by an amidotransferase. Since the well-characterized bacterial ND-GluRS enzymes recognize tRNAGlu and tRNAGln with an unrelated α-helical cage domain in contrast to the β-barrel anticodon-binding domain in archaeal and eukaryotic GluRSs, the mode of tRNAGlu/tRNAGln discrimination in archaea and eukaryotes was unknown. Here, we present the crystal structure of the Methanothermobacter thermautotrophicus ND-GluRS, which is the evolutionary predecessor of both the glutaminyl-tRNA synthetase (GlnRS) and the eukaryotic discriminating GluRS. Comparison with the previously solved structure of the Escherichia coli GlnRS-tRNAGln complex reveals the structural determinants responsible for specific tRNAGln recognition by GlnRS compared to promiscuous recognition of both tRNAs by the ND-GluRS. The structure also shows the amino acid recognition pocket of GluRS is more variable than that found in GlnRS. Phylogenetic analysis is used to reconstruct the key events in the evolution from indirect to direct genetic encoding of glutamine. 相似文献
992.
Background
The prevention of head injuries in alpine activities has focused on helmets. However, no systematic review has examined the effect of helmets on head and neck injuries among skiers and snowboarders.Methods
We searched electronic databases, conference proceedings and reference lists using a combination of the key words “head injury or head trauma,” “helmet” and “skiing or snowboarding.” We included studies that used a control group; compared skiers or snowboarders with and without helmets; and measured at least one objectively quantified outcome (e.g., head injury, and neck or cervical injury).Results
We included 10 case–control, 1 case–control/case-crossover and 1 cohort study in our analysis. The pooled odds ratio (OR) indicated that skiers and snowboarders with a helmet were significantly less likely than those without a helmet to have a head injury (OR 0.65, 95% confidence interval [CI] 0.55–0.79). The result was similar for studies that used controls without an injury (OR 0.61, 95% CI 0.36–0.92), those that used controls with an injury other than a head or neck injury (OR 0.63, 95% CI 0.52–0.80) and studies that included children under the age of 13 years (OR 0.41, 95% CI 0.27–0.59). Helmets were not associated with an increased risk of neck injury (OR 0.89, 95% CI 0.72–1.09).Interpretation
Our findings show that helmets reduce the risk of head injury among skiers and snowboarders with no evidence of an increased risk of neck injury.Skiing and snowboarding are popular winter activities.1 Estimates from numerous countries indicate that head injuries account for 9% to 19%, and neck injuries for 1% to 4%, of all injuries reported by ski patrols and emergency departments.2–11 Rates of head and neck injuries have been reported between 0.09 and 0.46 per 1000 outings.12 Head and neck injuries are disproportionately represented in cases of severe trauma, and traumatic brain injury is the leading cause of death and serious injury among skiers and snow-boarders.13 As far back as 1983, Oh and Schmid recommended mandatory helmet use for children while skiing.14Many studies of the relation between helmet use and head injuries among skiers and snowboarders have found a protective effect.15–24 It has been suggested that the use of helmets may increase the risk of neck injury in a crash or fall.25 This may be more evident among children because they have a greater head:body ratio than adults, and the additional size and weight of the helmet may increase the risk of neck injury in an otherwise routine fall.26 We conducted a systematic review of the effect of helmets on head and neck injuries among skiers and snowboarders. 相似文献993.
994.
995.
Five-day carbonaceous biochemical oxygen demand (CBOD5) removal efficiency was evaluated for the marshland upwelling system (MUS) under both intermediate and saltwater conditions. The MUS treated decentralized wastewater from two private camps and a public restroom in the Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi, and one private camp in the Barataria Terrebonne National Estuary, along Bayou Segnette, Louisiana. Raw wastewater was injected into the surrounding subsurface at a depth of 3.8 or 4.3 m. Various injection flow rates and frequencies were tested in addition to a synthetic wastewater trial. All trials followed a first-order background corrected removal equation, resulting in removal constants ranging from 0.49 to 3.32 m?1 and predicted surface concentrations from 5.7 to 33.0 mg L?1. CBOD5 (unfiltered) influent concentrations of 282 ± 173 mg L?1 were reduced to an overall effluent mean of 13 ± 13 mg L?1 by a vector distance of 7 m at Moss Point and from 365 ± 151 mg L?1 to 3.6 ± 7.6 mg L?1 by a vector distance of 6 m for Bayou Segnette. Of seven trials, only one failed to achieve effluent CBOD5 levels below a National Pollutant Discharge Elimination System (NPDES) standard level of 25 mg L?1. 相似文献
996.
Thalita G. Barros Sergio Pinheiro J. S. Williamson Amílcar Tanuri M. Gomes Jr Helena S. Pereira R. M. Brindeiro José B. A. Neto O. A. C. Antunes Estela M. F. Muri 《Amino acids》2010,38(3):701-709
In this paper, we describe the synthesis of a novel class of pseudo-peptides derived from isomannide and several oxazolones as potential inhibitors of serine proteases as well as preliminary pharmacological assays for hepatitis C. Hepatitis C, dengue and West Nile fever are among the most important flaviviruses that share one important serine protease enzyme. Serine proteases belong to the most studied class of proteolytic enzymes and are a primary target in the drug development field. Several pseudo-peptides were obtained in good yields from the reaction of isomannide and oxazolones, and their anti-HCV potential using the HCV replicon-based assay was shown. 相似文献
997.
Michael A. Chernousov Kelly Baylor Richard C. Stahl Mark M. Stecker Lynn Y. Sakai Sui Lee-Arteaga Francesco Ramirez David J. Carey 《Matrix biology》2010,29(5):357-368
The extracellular matrix of peripheral nerve is formed from a diverse set of macromolecules, including glycoproteins, collagens and proteoglycans. Recent studies using knockout animal models have demonstrated that individual components of the extracellular matrix play a vital role in peripheral nerve development and regeneration. In this study we identified fibrillin-1 and fibrillin-2, large modular structural glycoproteins, as components of the extracellular matrix of peripheral nerve. Previously it was found that fibrillin-2 null mice display joint contractures, suggesting a possible defect of the peripheral nervous system in these animals. Close examination of the peripheral nerves of fibrillin-2 deficient animals described here revealed some structural abnormalities in the perineurium, while general structure of the nerve and molecular composition of nerve extracellular matrix remained unchanged. We also found that in spite of the obvious motor function impairment, fibrillin-2 null mice failed to display changes of nerve conduction properties or nerve regeneration capacity. Based on the data obtained we can conclude that peripheral neuropathy should be excluded as the cause of the impairment of locomotory function and joint contractures observed in fibrillin-2 deficient animals. 相似文献
998.
Kelly C. Ryan Olivia E. Johnson Diane E. Cabelli Thomas C. Brunold Michael J. Maroney 《Journal of biological inorganic chemistry》2010,15(5):795-807
Nickel superoxide dismutase (NiSOD) is unique among the family of superoxide dismutase enzymes in that it coordinates Cys
residues (Cys2 and Cys6) to the redox-active metal center and exhibits a hexameric quaternary structure. To assess the role
of the Cys residues with respect to the activity of NiSOD, mutations of Cys2 and Cys6 to Ser (C2S-NiSOD, C6S-NiSOD, and C2S/C6S-NiSOD)
were carried out. The resulting mutants do not catalyze the disproportionation of superoxide, but retain the hexameric structure
found for wild-type NiSOD and bind Ni(II) ions in a 1:1 stoichiometry. X-ray absorption spectroscopic studies of the Cys mutants
revealed that the nickel active-site structure for each mutant resembles that of C2S/C6S-NiSOD and demonstrate that mutation
of either Cys2 or Cys6 inhibits coordination of the remaining Cys residue. Mutation of one or both Cys residue(s) in NiSOD
induces the conversion of the low-spin Ni(II) site in the native enzyme to a high-spin Ni(II) center in the mutants. This
result indicates that coordination of both Cys residues is required to generate the native low-spin configurations and maintain
catalytic activity. Analysis of the quaternary structure of the Cys mutants by differential scanning calorimetry, mass spectrometry,
and size-exclusion chromatography revealed that the Cys ligands, particularly Cys2, are also important for stabilizing the
hexameric quaternary structure of the native enzyme. 相似文献
999.
1000.
Oisín F. McD. Sweeney Mark W. Wilson Sandra Irwin Thomas C. Kelly John O’Halloran 《Biodiversity and Conservation》2010,19(8):2329-2342
This study compared the bird assemblages of native semi-natural woodlands and non-native Sitka spruce (Picea sitchensis) plantations in Ireland to identify what vegetation variables most influenced birds and to identify management targets in
plantations to maximise future bird conservation. Point counts were conducted in 10 Oak (Quercus spp.) and 10 Ash (Fraxinus excelsior) native woodlands and in five Mid-rotation (20–30 years old) and five Mature (30–50 years old) Sitka spruce plantations.
Ordination was used to characterise woodland types according to their constituent bird species. Total bird density (calculated
using Distance software) and species richness were assessed for the different woodland types. Oak and Ash woodland bird assemblages were
separated from Mid-rotation and Mature plantations by the ordination. There was no difference in total bird density between
any of the woodland types. Oak woodlands had significantly higher species richness than either Mid-rotation or Mature Sitka
spruce plantations. Ash had higher species richness than Mature Sitka spruce plantations. Understorey vegetation was negatively
associated with total bird density, which also varied with survey year. Understorey vegetation was positively associated with
species richness. Reasons for the relationships between vegetation and bird assemblages are discussed. Management should seek
to increase shrub and understorey vegetation in the Mid-rotation phase to improve the contribution of plantations to bird
conservation. 相似文献