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151.
Coastal barrens support rare plant species but may be threatened by forest encroachment. We determined whether trees spread
into coastal barren habitat from forest patches and assessed plant species composition and soil properties across the forest–barren
ecotone. We quantified tree age and height, soil properties, and vascular plant, bryophyte and lichen species composition
along transects perpendicular to the edges of tree patches within the forest–barren ecotone in coastal Nova Scotia. Randomization
tests assessed whether the vegetation and environmental characteristics were significantly different in the transition zone
compared to one or both adjoining ecosystems. We used ordination to examine trends in species composition across the ecotone
and the relationship to environmental variables. Tree age and height decreased continuously from the forest towards the edge
of the forest patches. There were also trends in vegetation composition and structure from the forest into the open barrens.
Many species were most abundant within the transition zone, although not always significantly. Soil properties were relatively
uniform across the ecotone. The structure and vegetation of the forest–barren ecotone suggests that forest patches act as
nuclei for forest expansion on barrens with a typical successional pathway where coastal barren vegetation is gradually replaced
by forest species. This encroachment may pose a threat to rare barrens communities. While landscape factors such as salt spray
and wind exposure may determine the general locations where forest can establish, biotic processes of growth and dispersal
appear to govern the fine-scale expansion of tree patches. 相似文献
152.
Preferences of female American goldfinches (Carduelis tristis) for natural and artificial male traits 总被引:1,自引:0,他引:1
We conducted two experiments to determine mating preferencesof female American goldfinches (Carduelis tristis). In the firstexperiment, females were allowed to choose among four naturallyvarying males. In the second, females chose among four maleswearing either orange, blue, yellow, or no color bands. In experiment1, females performed more courtship with males that had significantlybrighter bills and were brighter overall. In experiment 2, femalespreferred males wearing orange bands over unhanded males. Blue-bandedmales ranked second and yellow third, but neither was preferredsignificantly more often than the unbanded males. A female'spreference for a particular band color was weakly associatedwith her own bill and plumage measures; females with brighterthroat feathers and yellower bills preferred orange bands toblue bands. The results suggest that female preferences fororange and yellow may be functional and that females may alsohave aesthetic preferences. 相似文献
153.
Trehalose dihydrate is a safe, naturally occurring disaccharide used as a food ingredient and pharmaceutical excipient. It has been reported that room temperature milling does not lead to the formation of amorphous trehalose dihydrate. This paper reports the behaviour of trehalose dihydrate upon milling at cryogenic temperatures as studied by DSC, TGA, XRPD and Raman spectroscopy. We have demonstrated that the crystal to glass transformation for trehalose dihydrate is possible using cryogenic milling. This is the first reported example of cryogenic milling (a mild and widely applicable technique) applied to generating amorphous hydrates. 相似文献
154.
155.
Teplova M Malinina L Darnell JC Song J Lu M Abagyan R Musunuru K Teplov A Burley SK Darnell RB Patel DJ 《Structure (London, England : 1993)》2011,19(7):930-944
Nova onconeural antigens are neuron-specific RNA-binding proteins implicated in paraneoplastic opsoclonus-myoclonus-ataxia (POMA) syndrome. Nova harbors three K-homology (KH) motifs implicated in alternate splicing regulation of genes involved in inhibitory synaptic transmission. We report the crystal structure of the first two KH domains (KH1/2) of?Nova-1 bound to an in?vitro selected RNA hairpin, containing a UCAG-UCAC high-affinity binding site. Sequence-specific intermolecular contacts in the complex involve KH1 and the second UCAC repeat, with the RNA scaffold buttressed by interactions between repeats. Whereas the canonical RNA-binding surface of KH2 in the above complex engages in protein-protein interactions in the crystalline state, the individual KH2 domain can sequence-specifically target the UCAC RNA element in solution. The observed antiparallel alignment of KH1 and KH2 domains in the crystal structure of the complex generates a scaffold that could facilitate target pre-mRNA looping on Nova binding, thereby potentially explaining Nova's functional role in splicing regulation. 相似文献
156.
Structure,Dynamics, Evolution,and Function of a Major Scaffold Component in the Nuclear Pore Complex
Parthasarathy Sampathkumar Seung Joong Kim Paula Upla William J. Rice Jeremy Phillips Benjamin L. Timney Ursula Pieper Jeffrey B. Bonanno Javier Fernandez-Martinez Zhanna Hakhverdyan Natalia E. Ketaren Tsutomu Matsui Thomas M. Weiss David L. Stokes J. Michael Sauder Stephen K. Burley Andrej Sali Michael P. Rout Steven C. Almo 《Structure (London, England : 1993)》2013,21(4):560-571
157.
Ray SS Bonanno JB Rajashankar KR Pinho MG He G De Lencastre H Tomasz A Burley SK 《Structure (London, England : 1993)》2002,10(11):1499-1508
Cocrystal structures of Methanococcus jannaschii diaminopimelate decarboxylase (DAPDC) bound to a substrate analog, azelaic acid, and its L-lysine product have been determined at 2.6 A and 2.0 A, respectively. This PLP-dependent enzyme is responsible for the final step of L-lysine biosynthesis in bacteria and plays a role in beta-lactam antibiotic resistance in Staphylococcus aureus. Substrate specificity derives from recognition of the L-chiral center of diaminopimelate and a system of ionic "molecular rulers" that dictate substrate length. A coupled-enzyme assay system permitted measurement of kinetic parameters for recombinant DAPDCs and inhibition constants (K(i)) for azelaic acid (89 microM) and other substrate analogs. Implications for rational design of broad-spectrum antimicrobial agents targeted against DAPDCs of drug-resistant strains of bacterial pathogens, such as Staphylococcus aureus, are discussed. 相似文献
158.
Knutsen LJ Hobbs CJ Earnshaw CG Fiumana A Gilbert J Mellor SL Radford F Smith NJ Birch PJ Russell Burley J Ward SD James IF 《Bioorganic & medicinal chemistry letters》2007,17(3):662-667
A series of new N-type (Ca(v)2.2) calcium channel blockers derived from the 'hit' structures 2-(3-bromo-4-fluorophenyl)-3-(2-pyridin-2-ylethyl)thiazolidin-4-one 9 and its 2-[4-(4-bromophenyl)pyridin-3-yl]-3-isobutyl analogue 10 is described. Extensive SAR studies using a range of synthetic approaches resulted in novel, patented compounds with IC50 values of up to 0.2 microM in an in vitro IMR32 assay, and selectivities for N/L of up to 30-fold. The new compounds described have potential in treatment of neuropathic pain. 相似文献
159.