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121.
Nitrogen yield advantage from grass–legume mixtures is robust over a wide range of legume proportions and environmental conditions 下载免费PDF全文
Matthias Suter John Connolly John A. Finn Ralf Loges Laura Kirwan Maria‐Teresa Sebastià Andreas Lüscher 《Global Change Biology》2015,21(6):2424-2438
Current challenges to global food security require sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N), increased protein self‐sufficiency through homegrown crops, and reduced N losses to the environment. Such challenges were addressed in a continental‐scale field experiment conducted over 3 years, in which the amount of total nitrogen yield (Ntot) and the gain of N yield in mixtures as compared to grass monocultures (Ngainmix) was quantified from four‐species grass–legume stands with greatly varying legume proportions. Stands consisted of monocultures and mixtures of two N2‐fixing legumes and two nonfixing grasses. The amount of Ntot of mixtures was significantly greater (P ≤ 0.05) than that of grass monocultures at the majority of evaluated sites in all 3 years. Ntot and thus Ngainmix increased with increasing legume proportion up to one‐third of legumes. With higher legume percentages, Ntot and Ngainmix did not continue to increase. Thus, across sites and years, mixtures with one‐third proportion of legumes attained ~95% of the maximum Ntot acquired by any stand and had 57% higher Ntot than grass monocultures. Realized legume proportion in stands and the relative N gain in mixture (Ngainmix/Ntot in mixture) were most severely impaired by minimum site temperature (R = 0.70, P = 0.003 for legume proportion; R = 0.64, P = 0.010 for Ngainmix/Ntot in mixture). Nevertheless, the relative N gain in mixture was not correlated to site productivity (P = 0.500), suggesting that, within climatic restrictions, balanced grass–legume mixtures can benefit from comparable relative gains in N yield across largely differing productivity levels. We conclude that the use of grass–legume mixtures can substantially contribute to resource‐efficient agricultural grassland systems over a wide range of productivity levels, implying important savings in N fertilizers and thus greenhouse gas emissions and a considerable potential for climate change mitigation. 相似文献
122.
Wolf L. Eiserhardt Finn Borchsenius Christoffer M. Plum Alejandro Ordonez Jens‐Christian Svenning 《Ecology letters》2015,18(3):263-272
When taxa go extinct, unique evolutionary history is lost. If extinction is selective, and the intrinsic vulnerabilities of taxa show phylogenetic signal, more evolutionary history may be lost than expected under random extinction. Under what conditions this occurs is insufficiently known. We show that late Cenozoic climate change induced phylogenetically selective regional extinction of northern temperate trees because of phylogenetic signal in cold tolerance, leading to significantly and substantially larger than random losses of phylogenetic diversity (PD). The surviving floras in regions that experienced stronger extinction are phylogenetically more clustered, indicating that non‐random losses of PD are of increasing concern with increasing extinction severity. Using simulations, we show that a simple threshold model of survival given a physiological trait with phylogenetic signal reproduces our findings. Our results send a strong warning that we may expect future assemblages to be phylogenetically and possibly functionally depauperate if anthropogenic climate change affects taxa similarly. 相似文献
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Methionine sulfoxide reductases are antioxidant enzymes that repair oxidatively damaged methionine residues in proteins. Mammals have three members of the methionine-R-sulfoxide reductase family, including cytosolic MsrB1, mitochondrial MsrB2, and endoplasmic reticulum MsrB3. Here, we report the solution structure of reduced Mus musculus MsrB2 using high resolution nuclear magnetic resonance (NMR) spectroscopy. MsrB2 is a β-strand rich globular protein consisting of eight antiparallel β-strands and three N-terminal α-helical segments. The latter secondary structure elements represent the main structural difference between mammalian MsrB2 and MsrB1. Structural comparison of mammalian and bacterial MsrB structures indicates that the general topology of this MsrB family is maintained and that MsrB2 more resembles bacterial MsrBs than MsrB1. Structural and biochemical analysis supports the catalytic mechanism of MsrB2 that, in contrast to MsrB1, does not involve a resolving cysteine (Cys). pH dependence of catalytically relevant residues in MsrB2 was accessed by NMR spectroscopy and the pK(a) of the catalytic Cys162 was determined to be 8.3. In addition, the pH-dependence of MsrB2 activity showed a maximum at pH 9.0, suggesting that deprotonation of the catalytic Cys is a critical step for the reaction. Further mobility analysis showed a well-structured N-terminal region, which contrasted with the high flexibility of this region in MsrB1. Our study highlights important structural and functional aspects of mammalian MsrB2 and provides a unifying picture for structure-function relationships within the MsrB protein family. 相似文献
125.
Koltun E Richards S Chan V Nachtigall J Du H Noson K Galan A Aay N Hanel A Harrison A Zhang J Won KA Tam D Qian F Wang T Finn P Ogilvie K Rosen J Mohan R Larson C Lamb P Nuss J Kearney P 《Bioorganic & medicinal chemistry letters》2011,21(22):6773-6777
A novel series of potent inhibitors of glucosylceramide synthase are described. The optimization of biochemical and cellular potency as well as ADME properties led to compound 23c. Broad tissue distribution was obtained following oral administration to mice. Thus 23c could be another useful tool compound for studying the effects of GCS inhibition in vitro and in vivo. 相似文献
126.
Zhou Q Stefano JE Harrahy J Finn P Avila L Kyazike J Wei R Van Patten SM Gotschall R Zheng X Zhu Y Edmunds T Pan CQ 《Bioconjugate chemistry》2011,22(4):741-751
Engineering proteins for selective tissue targeting can improve therapeutic efficacy and reduce undesired side effects. The relatively high dose of recombinant human acid α-glucosidase (rhGAA) required for enzyme replacement therapy of Pompe disease may be attributed to less than optimal muscle uptake via the cation-independent mannose 6-phosphate receptor (CI-MPR). To improve muscle targeting, Zhu et al. (1) conjugated periodate oxidized rhGAA with bis mannose 6-phosphate bearing synthetic glycans and achieved 5-fold greater potency in a murine Pompe efficacy model. In the current study, we systematically evaluated multiple strategies for conjugation based on a structural homology model of GAA. Glycan derivatives containing succinimide, hydrazide, and aminooxy linkers targeting free cysteine, lysines, and N-linked glycosylation sites on rhGAA were prepared and evaluated in vitro and in vivo. A novel conjugation method using enzymatic oxidation was developed to eliminate side oxidation of methionine. Conjugates derived from periodate oxidized rhGAA still displayed the greatest potency in the murine Pompe model. The efficiency of conjugation and its effect on catalytic activity were consistent with predictions based on the structural model and supported its use in guiding selection of appropriate chemistries. 相似文献
127.
To increase student engagement, active participation, and performance, personal response systems (clickers) were incorporated into six lecture-based sections of four required courses within the Health Sciences Department major curriculum: freshman-level Anatomy and Physiology I and II, junior-level Exercise Physiology, and senior-level Human Pathophysiology. Clickers were used to gather anonymous student responses to questions posed within the class period after individual thought and peer discussion. Students (n = 293, 88% of students completing the courses) completed a perceptual survey on clicker effectiveness inserted into the Student Assessment of Learning Gains online instrument. Across courses and years, students uniformly rated several dimensions of clicker use as providing good to great gain in engaging them in active learning, increasing participation and involvement during class, maintaining attention, applying material immediately, providing feedback concerning their understanding, and offering an anonymous format for participation. Within these four sections, quiz grades were compared between clicker and nonclicker years. Significant increases in pre- and posttest scores were seen in Exercise Physiology in clicker years and on some, but not all material, in Anatomy and Physiology I and II based on content quizzes. Human Pathophysiology results were unexpected, with higher quiz scores in the nonclicker year. The results support the hypothesis of increased engagement with clicker use. The hypothesis of increased student performance was not consistently supported. Increased performance was seen in Exercise Physiology. In Anatomy and Physiology I and II, performance improved on some content quizzes. In Human Pathophysiology, performance did not improve with clickers. 相似文献
128.
A complex genomic rearrangement involving the endothelin 3 locus causes dermal hyperpigmentation in the chicken 总被引:2,自引:0,他引:2
Dorshorst B Molin AM Rubin CJ Johansson AM Strömstedt L Pham MH Chen CF Hallböök F Ashwell C Andersson L 《PLoS genetics》2011,7(12):e1002412
Dermal hyperpigmentation or Fibromelanosis (FM) is one of the few examples of skin pigmentation phenotypes in the chicken, where most other pigmentation variants influence feather color and patterning. The Silkie chicken is the most widespread and well-studied breed displaying this phenotype. The presence of the dominant FM allele results in extensive pigmentation of the dermal layer of skin and the majority of internal connective tissue. Here we identify the causal mutation of FM as an inverted duplication and junction of two genomic regions separated by more than 400 kb in wild-type individuals. One of these duplicated regions contains endothelin 3 (EDN3), a gene with a known role in promoting melanoblast proliferation. We show that EDN3 expression is increased in the developing Silkie embryo during the time in which melanoblasts are migrating, and elevated levels of expression are maintained in the adult skin tissue. We have examined four different chicken breeds from both Asia and Europe displaying dermal hyperpigmentation and conclude that the same structural variant underlies this phenotype in all chicken breeds. This complex genomic rearrangement causing a specific monogenic trait in the chicken illustrates how novel mutations with major phenotypic effects have been reused during breed formation in domestic animals. 相似文献
129.
Although membrane proteins are ubiquitous within all living organisms and represent the majority of drug targets, a general method for direct, label-free measurement of ligand binding to native membranes has not been reported. Here we show that backscattering interferometry (BSI) can accurately quantify ligand-receptor binding affinities in a variety of membrane environments. By detecting minute changes in the refractive index of a solution, BSI allows binding interactions of proteins with their ligands to be measured at picomolar concentrations. Equilibrium binding constants in the micromolar to picomolar range were obtained for small- and large-molecule interactions in both synthetic and cell-derived membranes without the use of labels or supporting substrates. The simple and low-cost hardware, high sensitivity and label-free nature of BSI should make it readily applicable to the study of many membrane-associated proteins of biochemical and pharmacological interest. 相似文献
130.