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141.
Summary A new computer-based approach is described for efficient sequence-specific assignment of uniformly 15N-labeled proteins. For this purpose three-dimensional 15N-correlated [1H, 1H]-NOESY spectra are divided up into two-dimensional 1H-1H strips which extend over the entire spectral width along one dimension and have a width of ca. 100 Hz, centered about the amide proton chemical shifts along the other dimension. A spectral correlation function enables sorting of these strips according to proximity of the corresponding residues in the amino acid sequence. Thereby, starting from a given strip in the spectrum, the probability of its corresponding to the C-terminal neighboring residue is calculated for all other strips from the similarity of their peak patterns with a pattern predicted for the sequentially adjoining residue, as manifested in the scalar product of the vectors representing the predicted and measured peak patterns. Tests with five different proteins containing both -helices and -sheets, and ranging in size from 58 to 165 amino acid residues show that the discrimination achieved between the sequentially neighboring residue and all other residues compares well with that obtained with an unguided interactive search of pairs of sequentially neighboring strips, with important savings in the time needed for complete analysis of 3D 15N-correlated [1H, 1H]-NOESY spectra. The integration of this routine into the program package XEASY ensures that remaining ambiguities can be resolved by visual inspection of the strips, combined with reference to the amino acid sequence and information on spin-system types obtained from additional NMR spectra.Abbreviations 1D, 2D, 3D, 4D
one-, two-, three-, four-dimensional
- NOE
nuclear Overhauser enhancement
- NOESY
nuclear Overhauser enhancement spectroscopy
- COSY
correlation spectroscopy
- TOCSY
total correlation spectroscopy 相似文献
142.
The severity of a root rot disease of cereals, caused by Rhizoctonia solani Kühn AG8, was inversely correlated to the Zn status of plants in field studies in 1989 and 1990. In 1989, a preliminary survey was conducted in a farmer's field in South Australia where Zn deficiency and disease were both widespread. Zn concentration in Spear wheat plants at the 3-leaf to early tillering stage was negatively correlated with severity of the disease. For the elevent elements analysed, a correlation matrix showed that Zn had the highest, and only significant (R2=0.52**) association with disease. The effect of Zn applications and their residual value on disease severity was further studied in a long-term field experiment in 1989 and 1990 to which Zn had been applied in 1986. There was a decrease in the area of Rhizoctonia bare patch as Zn rate was increased, a result consistent with the field survey results; the recommended rate of 2.5 kg Zn ha–1 reduced the area affected by bare patch from 42% to 21% of the total crop area compared with no Zn application, overcame Zn deficiency and increased grain yield from 1.1 to 2.8 t ha–1. In 1990, fresh Zn application treatments were applied to trial plots designed for this purpose, in order to compare the response with the older Zn treatments applied in 1986. The areas of bare patch in the older Zn treatments were approximately 5% greater than those in the fresh Zn treatments. The results are consistent with the hypothesis that Zn deficient plants are more susceptible to root rot caused by R. solani. Testing this hypothesis is the subject of a companion paper. 相似文献
143.
Gregory J. Connell Eric L. Christian 《Origins of life and evolution of the biosphere》1993,23(5-6):291-297
RNA has been hypothesized to have preceded proteins as the major catalysts of the biosphere, yet there are only a very limited number of chemical reactions that are known to be catalyzed by modern RNA. Cofactors are used by the majority of protein enzymes to supply additional functional groups to the active site. RNA should also be able to utilize some of these same cofactors to extend its own catalytic potential. We describe here how it could be possible to use selection — amplification from a population of random RNA to obtain a coenzyme A mediated RNA transacylase. Exploitation of some of the sulphur chemistry mediated by coenzyme A could have significantly expanded a prebiotic RNA directed metabolism. 相似文献
144.
Inci Arisan-Atac Regina Hodits Doris Kristufek Christian P. Kubicek 《Applied microbiology and biotechnology》1993,39(1):58-62
Trichoderma reesei was studied for its ability to produce -mannanase activity on a variety of carbon sources. The highest -mannanase activity was produced on cellulose, whereas -mannan-containing carbon sources (such as kojac powder or locust bean gum) gave lower enzyme titres. The enzyme responsible for the major -mannanolytic activity from T. reesei was purified to physical homogeneity by preparative chromatofocusing and anion exchange fast protein liquid chromatography. This -mannanase is a glycoprotein, with a molecular mass of 46 (±2) kDa and an isoelectric point of 5.2. It has an optimal pH at 5.0 and broad pH stability (2.5–7.0). It is stable for 60 min at 55° C, and has an optimal temperature for activity at 75° C. During incubation with locust bean gum, the enzyme releases mainly tri- and disaccharides.
Correspondence to: C. P. Kubicek 相似文献
145.
Christian Paul Ulrich Schoenwald Hans Truckenbrodt Maria P. Bettinotti Günter Brünnler Elisabeth Keller Claudia Nevinny-Stickel Zhu Yao Ekkehard D. Albert 《Immunogenetics》1993,37(6):442-448
We investigated the polymorphic second exon of the HLA-DPB1 and HLA-DRB1 genes, using in vitro DNA amplification by polymerase chain reaction (PCR) and oligonucleotide hybridization in 136 patients with early onset pauciarticular juvenile chronic arthritis (EOPA-JCA) and 199 healthy controls. The analysis of the HLA-DRB1 system revealed that most of the DRB1 alleles are not indifferent with respect to susceptibility to EOPA-JCA. There is a hierarchy of susceptible (DRB1*08, DR5), permissive (DRB1*01), moderately protective (DR2, DRB1*04), and protective (DRB1*07) alleles. In contrast, no hierarchy could be shown for the HLA-DPB1 system. DPB1*0201 was found to be susceptible. The relatively frequent alleles DPB1*0402 and DPB1*0401 seem to be indifferent. The associations with DPB1*0201, DR5, and DRB1*08 are independent of each other: that is to say they, are not brought about by linkage disequilibrium. The susceptible alleles DPB1*0201 and DR5 show evidence for interaction in the pathogenesis of EOPA-JCA. Interaction seems likely between DPB1*0201 and DRB1*08, DR5 and DRB1*08, or between DR6 and DRB1*08. The strongest interaction exists between DPB1*0201 and a common DQ factor associated with both DR5 and DRB1*08. Finally, we observed a hierarchy among the various marker combinations, where the risk of developing EOPA-JCA increases with the number of associated markers present in an individual.This work was supported by SFB217.The data presented here are part of the doctoral thesis of C. Paul. 相似文献
146.
Different propensity for spontaneous differentiation of cell clones isolated from the human ovarian surface epithelial cell line HOC-7 总被引:1,自引:0,他引:1
Thomas W. Grunt Helga Oeller Canatay Somay Christian Dittrich 《Differentiation; research in biological diversity》1993,53(1):45-50
Abstract. Limiting dilution culture of cell fractions obtained by discontinuous density gradient centrifugation was used to establish six different cell clones from HOC-7 ovarian adenocarcinoma cells (D1-D3, N1-N3). Clones D1-D3 revealed a phenotype similar to that seen in parental cells exposed to differentiation inducers such as dimethyl sulfoxide (DMSO, 0.8% [v/v]). They were flattened, slowly growing cells (doubling times: 42–46 h). The cells developed long cytoplasmic extensions and adopted a complicated growth pattern. Fixed-cell enzyme-linked immunosorbent assay (ELISA) and Western blotting demonstrated that these cells contained high levels of epidermal growth factor-receptor (EGF-R), carbohydrate antigen 125 (CA 125), fibronectin and desmoplakin, but low levels of myc oncoproteins. However, untreated parental cells and clones N1–N3 were fastgrowing (doubling times: 23–28 h), regularly shaped, polygonal cells ("cobblestone'monolayer) with low levels of EGF-R, CA 125, fibronectin and desmoplakin, but relatively higher amounts of myc oncoproteins. The similarity of the sublines to either untreated or inducertreated parental cells indicated that clones D1–D3 represented spontaneously differentiated HOC-7 cells, whereas clones N1–N3 originated from less-differentiated cells. The features examined in this model cell system proved to be closely related to ovarian cancer cell proliferation and differentiation. The observation of a tumorinherent propensity for spontaneous differentiation suggests that exogenous stimulation of existing differentiation pathways may represent an alternative approach for tackling the problem of growth control and differentiation in malignant tissues. 相似文献
147.
The eighth component of human complement (C8) is a serum protein that consists of three chains (, and ), encoded by three separate genes, viz., C8A, C8B, and C8G. In serum, the -subunit is non-covalently bound to the disulfide-linked - subunit. Using a full-length C8 cDNA probe, we isolated several clones from human genomic DNA libraries. Four clones covering the complete cDNA sequence were characterized by TaqI restriction mapping and were shotgun subcloned into M13. C8-cDNA-positive clones were partially sequenced to characterize the 12 exons of the gene with sizes from 69 to 347 bp. All intron-exon junctions followed the GT-AG rule. By using polymerase chain reaction (PCR) primers located in the adjacent intron sequences, all 12 exons of the C8B gene could be amplified from genomic DNA. All fragments showed the expected sizes. The sizes of eight introns could be determined by using primer pairs that amplified two exons and the enclosed intron, and by restriction mapping. These analyses and the insert sizes of the genomic clones indicate that the C8B gene has a total size of approximately 40 kb. The polymorphic TaqI site of the C8B gene localized in intron 11 could be demonstrated by direct restriction fragment analysis of a PCR fragment containing exons 11 and 12, and the enclosed intron 11. Homology comparison of the C8B gene with C8A and C9 on the basis of the exon structure confirmed the ancestral relationship known from the protein level. 相似文献
148.
Donatella Zona Peter M. Lafleur Koen Hufkens Beniamino Gioli Barbara Bailey George Burba Eugénie S. Euskirchen Jennifer D. Watts Kyle A. Arndt Mary Farina John S. Kimball Martin Heimann Mathias Göckede Martijn Pallandt Torben R. Christensen Mikhail Mastepanov Efrén López-Blanco Albertus J. Dolman Roisin Commane Charles E. Miller Josh Hashemi Lars Kutzbach David Holl Julia Boike Christian Wille Torsten Sachs Aram Kalhori Elyn R. Humphreys Oliver Sonnentag Gesa Meyer Gabriel H. Gosselin Philip Marsh Walter C. Oechel 《Global Change Biology》2023,29(5):1267-1281
Long-term atmospheric CO2 concentration records have suggested a reduction in the positive effect of warming on high-latitude carbon uptake since the 1990s. A variety of mechanisms have been proposed to explain the reduced net carbon sink of northern ecosystems with increased air temperature, including water stress on vegetation and increased respiration over recent decades. However, the lack of consistent long-term carbon flux and in situ soil moisture data has severely limited our ability to identify the mechanisms responsible for the recent reduced carbon sink strength. In this study, we used a record of nearly 100 site-years of eddy covariance data from 11 continuous permafrost tundra sites distributed across the circumpolar Arctic to test the temperature (expressed as growing degree days, GDD) responses of gross primary production (GPP), net ecosystem exchange (NEE), and ecosystem respiration (ER) at different periods of the summer (early, peak, and late summer) including dominant tundra vegetation classes (graminoids and mosses, and shrubs). We further tested GPP, NEE, and ER relationships with soil moisture and vapor pressure deficit to identify potential moisture limitations on plant productivity and net carbon exchange. Our results show a decrease in GPP with rising GDD during the peak summer (July) for both vegetation classes, and a significant relationship between the peak summer GPP and soil moisture after statistically controlling for GDD in a partial correlation analysis. These results suggest that tundra ecosystems might not benefit from increased temperature as much as suggested by several terrestrial biosphere models, if decreased soil moisture limits the peak summer plant productivity, reducing the ability of these ecosystems to sequester carbon during the summer. 相似文献
149.
Jörg Müller Oliver Mitesser Marc W. Cadotte Fons van der Plas Akira S. Mori Christian Ammer Anne Chao Michael Scherer-Lorenzen Petr Baldrian Claus Bässler Peter Biedermann Simone Cesarz Alice Claßen Benjamin M. Delory Heike Feldhaar Andreas Fichtner Torsten Hothorn Claudia Kuenzer Marcell K. Peters Kerstin Pierick Thomas Schmitt Bernhard Schuldt Dominik Seidel Diana Six Ingolf Steffan-Dewenter Simon Thorn Goddert von Oheimb Martin Wegmann Wolfgang W. Weisser Nico Eisenhauer 《Global Change Biology》2023,29(6):1437-1450
Intensification of land use by humans has led to a homogenization of landscapes and decreasing resilience of ecosystems globally due to a loss of biodiversity, including the majority of forests. Biodiversity–ecosystem functioning (BEF) research has provided compelling evidence for a positive effect of biodiversity on ecosystem functions and services at the local (α-diversity) scale, but we largely lack empirical evidence on how the loss of between-patch β-diversity affects biodiversity and multifunctionality at the landscape scale (γ-diversity). Here, we present a novel concept and experimental framework for elucidating BEF patterns at α-, β-, and γ-scales in real landscapes at a forest management-relevant scale. We examine this framework using 22 temperate broadleaf production forests, dominated by Fagus sylvatica. In 11 of these forests, we manipulated the structure between forest patches by increasing variation in canopy cover and deadwood. We hypothesized that an increase in landscape heterogeneity would enhance the β-diversity of different trophic levels, as well as the β-functionality of various ecosystem functions. We will develop a new statistical framework for BEF studies extending across scales and incorporating biodiversity measures from taxonomic to functional to phylogenetic diversity using Hill numbers. We will further expand the Hill number concept to multifunctionality allowing the decomposition of γ-multifunctionality into α- and β-components. Combining this analytic framework with our experimental data will allow us to test how an increase in between patch heterogeneity affects biodiversity and multifunctionality across spatial scales and trophic levels to help inform and improve forest resilience under climate change. Such an integrative concept for biodiversity and functionality, including spatial scales and multiple aspects of diversity and multifunctionality as well as physical and environmental structure in forests, will go far beyond the current widely applied approach in forestry to increase resilience of future forests through the manipulation of tree species composition. 相似文献
150.
Jeffrey D. Wood Lianhong Gu Paul J. Hanson Christian Frankenberg Lawren Sack 《Global Change Biology》2023,29(7):2015-2029
Soil and atmospheric droughts increasingly threaten plant survival and productivity around the world. Yet, conceptual gaps constrain our ability to predict ecosystem-scale drought impacts under climate change. Here, we introduce the ecosystem wilting point (ΨEWP), a property that integrates the drought response of an ecosystem's plant community across the soil–plant–atmosphere continuum. Specifically, ΨEWP defines a threshold below which the capacity of the root system to extract soil water and the ability of the leaves to maintain stomatal function are strongly diminished. We combined ecosystem flux and leaf water potential measurements to derive the ΨEWP of a Quercus-Carya forest from an “ecosystem pressure–volume (PV) curve,” which is analogous to the tissue-level technique. When community predawn leaf water potential (Ψpd) was above ΨEWP (=−2.0 MPa), the forest was highly responsive to environmental dynamics. When Ψpd fell below ΨEWP, the forest became insensitive to environmental variation and was a net source of carbon dioxide for nearly 2 months. Thus, ΨEWP is a threshold defining marked shifts in ecosystem functional state. Though there was rainfall-induced recovery of ecosystem gas exchange following soaking rains, a legacy of structural and physiological damage inhibited canopy photosynthetic capacity. Although over 16 growing seasons, only 10% of Ψpd observations fell below ΨEWP, the forest is commonly only 2–4 weeks of intense drought away from reaching ΨEWP, and thus highly reliant on frequent rainfall to replenish the soil water supply. We propose, based on a bottom-up analysis of root density profiles and soil moisture characteristic curves, that soil water acquisition capacity is the major determinant of ΨEWP, and species in an ecosystem require compatible leaf-level traits such as turgor loss point so that leaf wilting is coordinated with the inability to extract further water from the soil. 相似文献