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Question: Predictive vegetation modelling relies on the use of environmental variables, which are usually derived from abase data set with some level of error, and this error is propagated to any subsequently derived environmental variables. The question for this study is: What is the level of error and uncertainty in environmental variables based on the error propagated from a Digital Elevation Model (DEM) and how does it vary for both direct and indirect variables? Location: Kioloa region, New South Wales, Australia Methods: The level of error in a DEM is assessed and used to develop an error model for analysing error propagation to derived environmental variables. We tested both indirect (elevation, slope, aspect, topographic position) and direct (average air temperature, net solar radiation, and topographic wetness index) variables for their robustness to propagated error from the DEM. Results: It is shown that the direct environmental variable net solar radiation is less affected by error in the DEM than the indirect variables aspect and slope, but that regional conditions such as slope steepness and cloudiness can influence this outcome. However, the indirect environmental variable topographic position was less affected by error in the DEM than topographic wetness index. Interestingly, the results disagreed with the current assumption that indirect variables are necessarily less sensitive to propagated error because they are less derived. Conclusions: The results indicate that variables exhibit both systematic bias and instability under uncertainty. There is a clear need to consider the sensitivity of variables to error in their base data sets in addition to the question of whether to use direct or indirect variables.  相似文献   

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Question: Does the introduced pathogen Phytophthora cinnamomi change Banksia woodland α‐ or β‐diversity and what are the implications for species re‐colonization? Location: High rainfall zone of the Southwest Australian Floristic Region (SWAFR). Methods: We measured pathogen‐induced floristic change along a disease chronosequence, and re‐sampled historic quadrats in Banksia attenuata woodlands of the SWAFR. The chronosequence represents three disease stages: (1) healthy vegetation with no disease expression; (2) the active disease front; and (3) diseased vegetation infected for at least 15 years. Comparative data were obtained by resampling diseased plots that were historically disease‐free when established in 1990. Results: β‐diversity differed substantially for both chronosequence and historic data, while α‐diversity was maintained, as measured by plot species richness and Simpson's reciprocal index. Species of known pathogen susceptibility were significantly reduced in cover–abundance, including the structurally dominant species; Banksia attenuata, B. ilicifolia and Allocasuarina fraseriana. Although these species remained present on diseased sites, there were overall reductions in canopy closure, leaf litter and basal area. These declines were coupled with an increase of species with unknown susceptibility, suggesting potential resistance and capacity to take advantage of altered site conditions. Conclusions: This study highlights the ability of an introduced plant pathogen to alter community floristics and associated stand variables. Species cover–abundances are unlikely to recover due to a reduced seed source, altered site conditions and pathogen persistence at the landscape level. However, maintenance of α‐diversity suggests continued biological significance of Phytophthora‐affected sites and the formation of novel ecosystems, themselves worthy of conservation.  相似文献   

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Cell motility is dependent on a dynamic meshwork of actin filaments that is remodelled continuously. A large number of associated proteins that are severs, cross‐links, or caps the filament ends have been identified and the actin cross‐linker α‐actinin has been implied in several important cellular processes. In Entamoeba histolytica, the etiological agent of human amoebiasis, α‐actinin is believed to be required for infection. To better understand the role of α‐actinin in the infectious process we have determined the solution structure of the C‐terminal calmodulin‐like domain using NMR. The final structure ensemble of the apo form shows two lobes, that both resemble other pairs of calcium‐binding EF‐hand motifs, connected with a mobile linker. Proteins 2016; 84:461–466. © 2016 Wiley Periodicals, Inc.  相似文献   

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The adaptation of nine species of mites that infest stored products for starch utilization was tested by (1) enzymatic analysis using feces and whole mite extracts, (2) biotests, and (3) inhibition experiments. Acarus siro, Aleuroglyphus ovatus, and Tyroborus lini were associated with the starch‐type substrates and maltose, with higher enzymatic activities observed in whole mite extracts. Lepidoglyphus destructor was associated with the same substrates but had higher activities in feces. Dermatophagoides farinae, Chortoglyphus arcuatus, and Caloglyphus redickorzevi were associated with sucrose. Tyrophagus putrescentiae and Carpoglyphus lactis had low or intermediate enzymatic activity on the tested substrates. Biotests on starch additive diets showed accelerated growth of species associated with the starch‐type substrates. The inhibitor acarbose suppressed starch hydrolysis and growth of the mites. We suggest that the species with higher starch hydrolytic activity in feces were more tolerant to acarbose, and α‐amylase and α‐glucosidase of synanthropic mites are suitable targets for inhibitor‐based strategies of mite control. © 2009 Wiley Periodicals, Inc.  相似文献   

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Inflammatory cytokines are closely related to pigmentary changes. In this study, the effects of IFN‐γ on melanogenesis were investigated. IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis in B16 melanoma cells and normal human melanocytes. MITF mRNA and protein expressions were significantly inhibited in response to IFN‐γ. IFN‐γ inhibited CREB binding to the MITF promoter but did not affect CREB phosphorylation. Instead, IFN‐γ inhibited the association of CBP and CREB through the increased association between CREB binding protein (CBP) and STAT1. These findings suggest that IFN‐γ inhibits both basal and α‐MSH‐induced melanogenesis by inhibiting MITF expression. The inhibitory action of IFN‐γ in α‐MSH‐induced melanogenesis is likely to be associated with the sequestration of CBP via the association between CBP and STAT1. These data suggest that IFN‐γ plays a role in controlling inflammation‐ or UV‐induced pigmentary changes.  相似文献   

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5α‐Androst‐16‐en‐3α‐ol (α‐androstenol) is an important contributor to human axilla sweat odor. It is assumed that α‐andostenol is excreted from the apocrine glands via a H2O‐soluble conjugate, and this precursor was formally characterized in this study for the first time in human sweat. The possible H2O‐soluble precursors, sulfate and glucuronide derivatives, were synthesized as analytical standards, i.e., α‐androstenol, β‐androstenol sulfates, 5α‐androsta‐5,16‐dien‐3β‐ol (β‐androstadienol) sulfate, α‐androstenol β‐glucuronide, α‐androstenol α‐glucuronide, β‐androstadienol β‐glucuronide, and α‐androstenol β‐glucuronide furanose. The occurrence of α‐androstenol β‐glucuronide was established by ultra performance liquid chromatography (UPLC)/MS (heated electrospray ionization (HESI)) in negative‐ion mode in pooled human sweat, containing eccrine and apocrine secretions and collected from 25 female and 24 male underarms. Its concentration was of 79 ng/ml in female secretions and 241 ng/ml in male secretions. The release of α‐androstenol was observed after incubation of the sterile human sweat or α‐androstenol β‐glucuronide with a commercial glucuronidase enzyme, the urine‐isolated bacteria Streptococcus agalactiae, and the skin bacteria Staphylococcus warneri DSM 20316, Staphylococcus haemolyticus DSM 20263, and Propionibacterium acnes ATCC 6919, reported to have β‐glucuronidase activities. We demonstrated that if α‐ and β‐androstenols and androstadienol sulfates were present in human sweat, their concentrations would be too low to be considered as potential precursors of malodors; therefore, the H2O‐soluble precursor of α‐androstenol in apocrine secretion should be a β‐glucuronide.  相似文献   

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A conformational analysis of peptides having dipropylglycine (Dpg) or 1‐aminocycloheptanecarboxylic acid (Ac7c) within l ‐leucine (Leu) residues was conducted in solution and in a crystal state. Dpg and Ac7c had similar structures with acyclic and cyclic side chains, respectively. FTIR, 1H NMR, and CD spectra measurements revealed that the preferred conformations of Dpg‐ and Ac7c‐containing l ‐Leu peptides in solution were similar; both had a right‐handed (P) 310‐helix. The Dpg‐containing octapeptide adopted a right‐handed (P) α‐helix in the crystal state. Dpg and Ac7c homopeptides had planar and helical structures as their preferred conformations, respectively; however, Dpg‐ and Ac7c‐containing l ‐Leu peptides adopted similar structures in solution. © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 210–218, 2016.  相似文献   

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TTHA0281 is a hypothetical protein from Thermus thermophilus HB8 that belongs to an uncharacterized protein family, UPF0150, in the Pfam database and to COG1598 in the National Center for Biotechnology Information Database of Clusters of Orthologous Groups. The X‐ray crystal structure of the protein was determined by a multiple‐wavelength anomalous dispersion technique and was refined at 1.9 Å resolution to a final R factor of 18.5%. The TTHA0281 monomer adopts an α‐β‐β‐β‐α fold and forms a homotetramer. Based on the properties and functions of structural homologues of the TTHA0281 monomer, the TTHA0281 protein is speculated to be involved in RNA metabolism, including RNA binding and cleavage.  相似文献   

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This is a report on the structure determination of AmyB, the second α‐amylase from Halothermothrix orenii, by X‐ray crystallography. This bacterium was isolated from saltpans where conditions consisted of both high temperatures and high NaCl content. AmyB is a 599‐­residue protein which is stable and significantly active at 358 K in starch solution containing up to 10%(w/v) NaCl. The purified recombinant AmyB protein crystallizes in the monoclinic space group C2, with unit‐cell parameters a = 225.85, b = 77.16, c = 50.13 Å, β = 99.32°, using the hanging‐drop vapour‐diffusion method. The crystal diffracts X‐­rays to a resolution limit of 1.97 Å.  相似文献   

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The conformational characteristics of protected homo‐oligomeric Boc‐[β3(R)Val]n‐OMe, n = 1, 2, 3, 4, 6, 9, and 12 have been investigated in organic solvents using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) absorption spectroscopy and circular dichroism (CD) methods. The detailed 1H NMR analysis of Boc‐[β3(R)Val]12‐OMe reveals that the peptide aggregates extensively in CDCl3, but is disaggregated in 20%, (v/v) dimethyl sulfoxide (DMSO) in CDCl3 and in CD3OH. Limited assignment of the N‐terminus NH groups, together with solvent dependence of NH chemical shifts and temperature coefficients provides evidence for 14‐helix conformation in the 12‐residue peptide. FTIR analysis in CHCl3 establishes that the onset of folding and aggregation, as evidenced by NH stretching bands at 3375 cm−1 (intramolecular) and 3285 cm−1 (intermolecular), begins at the level of the tetrapeptide. The observed CD bands, 214 nm (negative) and 198 nm (positive), support 14‐helix formation in the 9 and 12 residue sequences. The folding and aggregation tendencies of homo‐oligomeric α‐, β‐, and γ‐ residues is compared in the model peptides Boc‐[ωVal]n‐NHMe, ω = α, β, and γ and n = 1, 2, and 3. Analysis of the FTIR spectra in CHCl3, establish that the tendency to aggregate at the di and tripeptide level follows the order β > α∼γ, while the tendency to fold follows the order γ > β > α.  相似文献   

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The activity of interferon‐γ (IFN‐γ) relies on signal transduction, which is triggered by combination with the receptors interferon‐γ receptor α chain (IFNGR1) and β chain (IFNGR2). Native recombinant chicken IFNGR1 (chIFNGR1; residues 25–237) was overexpressed in Escherichia coli, purified by refolding and crystallized using the vapour‐diffusion technique. The crystals belonged to space group P6522, with unit‐cell parameters a = b = 64.1, c = 216.3 Å, α = β = 90, γ = 120°. The Matthews coefficient and solvent content were calculated as 2.67 Å3 Da−1 and 53.97%, respectively. X‐ray diffraction data for chIFNGR1 were collected to 2.0 Å resolution at a synchrotron source.  相似文献   

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Because cadmium might interact with proteins and, thus, exert toxicity in organisms, it is vital to understand the molecular mechanism of the interaction between cadmium and biologically relevant proteins as well as the structural and functional changes in these proteins. In this study, the interaction between α‐chymotrypsin (α‐ChT) and cadmium chloride (CdCl2) was investigated by performing enzyme activity determinations, multispectroscopic measurements, isothermal titration calorimetry, and molecular docking studies. It was demonstrated that CdCl 2 binds to α‐ChT mainly via electrostatic forces with (21.0 ± 0.982) binding sites, leading to the increase of α‐helix and the decrease of β‐sheet. The interaction between CdCl 2 and α‐ChT loosened the protein skeleton and increased the molecular volume of α‐ChT. CdCl 2 first binds to the interface of α‐ChT and then interacts with the key residues His 57 or Asp 102 or both in the active sites, leading to the activity inhibition of α‐ChT under the exposure of high CdCl 2 concentrations.  相似文献   

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A single chiral cyclic α,α‐disubstituted amino acid with side‐chain methoxymethyl (MOM) protecting groups, (3S,4S)−1‐amino‐(3,4‐dimethoxymethoxy)cyclopentanecarboxylic acid [(S, S)‐Ac5cdOMOM], or side‐chain hydroxy groups, (3S,4S)−1‐amino‐(3,4‐dihydroxy)cyclopentanecarboxylic acid [(S, S)‐Ac5cdOH], was attached to the N‐terminal or C‐terminal position of α‐aminoisobutyric acid (Aib) tetrapeptide segments; i.e., we designed and synthesized four pentapeptides, Cbz‐[(S, S)‐Ac5cdOMOM]‐(Aib)4‐OEt ( 1 ), Cbz‐[(S, S)‐Ac5cdOH]‐(Aib)4‐OEt ( 2 ), Cbz‐(Aib)4‐[(S, S)‐Ac5cdOMOM]‐OMe ( 3 ), and Cbz‐(Aib)4‐[(S, S)‐Ac5cdOH]‐OMe ( 4 ). We then analyzed the peptides’ structures in the crystalline state. The four peptides all folded into 310‐helical structures; 1 formed a left‐handed (M) 310‐helix, 2 formed a mixture of right‐handed (P) and (M) 310‐helices, 3 formed a mixture of (P) and (M) 310‐helices, and 4 formed a (P) 310‐helix, respectively. In packing mode, the molecules of peptides 1 and 3 , which both possessed an Ac5cdOMOM residue, were connected by intermolecular hydrogen bonds along the peptide backbone (N H···O type). On the other hand, the packing of peptides 2 and 4 , which both contained an Ac5cdOH residue, was based on intermolecular hydrogen bonds derived from both the peptide backbone and the side‐chain hydroxy groups of the amino acid Ac5cdOH (O H···O type). © 2016 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 757–768, 2016.  相似文献   

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The hyperthermophilic crenarchaeon Ignicoccus hospitalis KIN4/I possesses at least 35 putative genes encoding enzymes that belong to the α/β‐hydrolase superfamily. One of those genes, the metallo‐hydrolase‐encoding igni18, was cloned and heterologously expressed in Pichia pastoris. The enzyme produced was purified in its catalytically active form. The recombinant enzyme was successfully crystallized and the crystal diffracted to a resolution of 2.3 Å. The crystal belonged to space group R32, with unit‐cell parameters a = b = 67.42, c = 253.77 Å, α = β = 90.0, γ = 120.0°. It is suggested that it contains one monomer of Igni18 within the asymmetric unit.  相似文献   

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Thermotoga maritima 4‐α‐glucanotransferase (GTase), a 52 kDa molecular‐weight amylolytic enzyme, has been crystallized by the hanging‐drop vapour‐diffusion method using PEG monomethylether 5000 as a precipitating agent. A complete data set has been collected to 2.6 Å resolution using cryocooling conditions and synchrotron radiation. The crystals belong to space group I222 or I212121, with unit‐cell parameters a = 92.6, b = 180.3, c = 199.2 Å.  相似文献   

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