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21.
Rafael AP Guércio Anna Shevchenko Andrej Shevchenko Jorge L López-Lozano Jaime Paba Marcelo V Sousa Carlos AO Ricart 《Proteome science》2006,4(1):11-14
Background
Bothrops atrox is responsible for the majority of snakebite accidents in the Brazilian Amazon region. Previous studies have demonstrated that the biological and pharmacological activities of B. atrox venom alter with the age of the animal. Here, we present a comparative proteome analysis of B. atrox venom collected from specimens of three different stages of maturation: juveniles, sub-adults and adults. 相似文献22.
Anaerobic growth of Paracoccus denitrificans requires cobalamin: characterization of cobK and cobJ genes
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A pleiotropic mutant of Paracoccus denitrificans, which has a severe defect that affects its anaerobic growth when either nitrate, nitrite, or nitrous oxide is used as the terminal electron acceptor and which is also unable to use ethanolamine as a carbon and energy source for aerobic growth, was isolated. This phenotype of the mutant is expressed only during growth on minimal media and can be reversed by addition of cobalamin (vitamin B(12)) or cobinamide to the media or by growth on rich media. Sequence analysis revealed the mutation causing this phenotype to be in a gene homologous to cobK of Pseudomonas denitrificans, which encodes precorrin-6x reductase of the cobalamin biosynthesis pathway. Convergently transcribed with cobK is a gene homologous to cobJ of Pseudomonas denitrificans, which encodes precorrin-3b methyltransferase. The inability of the cobalamin auxotroph to grow aerobically on ethanolamine implies that wild-type P. denitrificans (which can grow on ethanolamine) expresses a cobalamin-dependent ethanolamine ammonia lyase and that this organism synthesizes cobalamin under both aerobic and anaerobic growth conditions. Comparison of the cobK and cobJ genes with their orthologues suggests that P. denitrificans uses the aerobic pathway for cobalamin synthesis. It is paradoxical that under anaerobic growth conditions, P. denitrificans appears to use the aerobic (oxygen-requiring) pathway for cobalamin synthesis. Anaerobic growth of the cobalamin auxotroph could be restored by the addition of deoxyribonucleosides to minimal media. These observations provide evidence that P. denitrificans expresses a cobalamin-dependent ribonucleotide reductase, which is essential for growth only under anaerobic conditions. 相似文献
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25.
The influences of habitat, landscape structure and climate on local distribution patterns of the nuthatch (Sitta europaea L.) 总被引:1,自引:0,他引:1
P. E. Bellamy N. J. Brown B. Enoksson L. G. Firbank R. J. Fuller S. A. Hinsley A. G. M. Schotman 《Oecologia》1998,115(1-2):127-136
The nuthatch, Sitta europaea L., is a small (23 g), cavity-nesting woodland bird which, since the 1970s, has been expanding its range in Britain. However,
within this range, the species is notably scarce in an area of eastern England. This gap in the species distribution could
arise for several reasons including habitat quality, local landscape structure, regional landscape structure and climate.
Field surveys and logistic models of breeding nuthatch presence/absence were used to investigate the relative influences of
habitat quality, landscape structure and climate on the prevalence of nuthatches in eastern England. Field surveys of woods
in the study area indicated that habitat quality was sufficient to support a nuthatch population. A model of habitat occupancy
in relation to local landscape structure, developed in the Netherlands, was applied to the study area. The number of breeding
pairs predicted for the study area by the model was lower than expected from habitat area alone, suggesting an additional
effect of isolation. However, observed numbers were even lower than those predicted by the model. To evaluate the possible
roles of climate and large-scale landscape structure on distribution, presence/absence data of breeding nuthatches at the
10-km grid square scale were related to variables describing climate and the amount and dispersion of broadleaved woodland.
While climate in the study area appeared suitable, models including landscape variables suggested that the study area as a
whole was unlikely to support nuthatches. Although suitable habitat was available, woodland in the study area appeared to
be too isolated from surrounding nuthatch populations for colonisation to be successful. This situation may change if current
increases in both national and regional populations continue, thus increasing the number of potential colonists reaching the
study area.
Received: 3 November 1997 / 22 January 1998 相似文献
26.
Females of the sea urchin Strongylocentrotus purpuratus differ in the structures of their egg jelly sulfated fucans 总被引:1,自引:0,他引:1
The egg jelly coats of sea urchins contain sulfated fucans which bind to a
sperm surface receptor glycoprotein to initiate the signal transduction
events resulting in the sperm acrosome reaction. The acrosome reaction is
an ion channel regulated exocytosis which is an obligatory event for sperm
binding to, and fusion with, the egg. Approximately 90% of individual
females of the sea urchin Strongylocentrotus purpuratus spawned eggs having
only one of two possible sulfated fucan electrophoretic isotypes, a slow
migrating (sulfated fucan I), or a fast migrating (sulfated fucan II)
isotype. The remaining 10% of females spawned eggs having both sulfated
fucan isotypes. The two sulfated fucan isotypes were purified from egg
jelly coats and their structures determined by NMR spectroscopy and
methylation analysis. Both sulfated fucans are linear polysaccharides
composed of 1-->3-linked alpha-L-fucopyranosyl units. Sulfated fucan I
is entirely sulfated at the O -2 position but with a heterogeneous
sulfation pattern at O -4 position. Sulfated fucan II is composed of a
regular repeating sequence of 3 residues, as follows: [3-alpha-L-Fuc p -
2,4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-
1]n. Both purified sulfated fucans have approximately equal potency in
inducing the sperm acrosome reaction. The significance of two structurally
different sulfated fucans in the egg jelly coat of this species could
relate to the finding that the sperm receptor protein which binds sulfated
fucan contains two carbohydrate recognition modules of the C-type lectin
variety which differ by 50% in their primary structure.
相似文献
27.
Fucose is a major constituent of the protein- and lipid-linked glycans of
the various life-cycle stages of schistosomes. These fucosylated glycans
are highly antigenic and seem to play a role in the pathology of
schistosomiasis. In this article we describe the identification and
characterization of two fucosyltransferases (FucTs) in cercariae of the
avian schistosome Trichobilharzia ocellata, a GDP-Fuc:[Galbeta1--
>4]GlcNAcbeta-R alpha1-->3-FucT and a novel GDP-Fuc:Fucalpha-R
alpha1-- >2-FucT. Triton X-100 extracts of cercariae were assayed for
FucT activity using a variety of acceptor substrates. Type 1 chain
(Galbeta1- ->3GlcNAc) based compounds were poor acceptors, whereas those
based on a type 2 chain (Galbeta1-->4GlcNAc), whether
alpha2'-fucosylated, alpha3'-sialylated, or unsubstituted, and whether
present as oligosaccharide or contained in a glycopeptide or glycoprotein,
all served as acceptor substrates. In this respect the schistosomal alpha3-
FucT resembles human FucT V and VI rather than other known FucTs. N-
ethylmaleimide, an inhibitor of several human FucTs, had no effect on the
activity of the schistosomal alpha3-FucT, whereas GDP-beta-S was strongly
inhibitory. Large scale incubations were carried out with
Galbeta1-->4GlcNAc, GalNAcbeta1-->4GlcNAcbeta-O -(CH2)8COOCH3 and
Fucalpha1-->3GlcNAcbeta1-->2Man as acceptor substrates and the
products of the incubations were isolated using a sequence of
chromatographic techniques. By methylation analysis and 2D-TOCSY and
ROESY1H-NMR spectroscopy the products formed were shown to be Galbeta1--
>4[Fucalpha1-->2Fucalpha1-->3]GlcNAc,
GalNAcbeta1-->4[Fucalpha1-- >2Fucalpha1-->3]GlcNAcbe
ta-O-(CH2)8COOCH3, and Fucalpha1-->2Fucalpha1--
>3GlcNAcbeta1-->2Man, respectively. It is concluded that the alpha2-
FucT and alpha3-FucT are involved in the biosynthesis of the (oligomeric)
Lewisx sequences and the Fucalpha1-->2Fucalpha1-->3GlcNAc structural
element that have been described on schistosomal glycoconjugates.
相似文献
28.
29.
On efficient probability forecasting systems 总被引:1,自引:0,他引:1
30.
Richard F. Pywell Matthew S. Heard Ben A. Woodcock Shelley Hinsley Lucy Ridding Marek Nowakowski James M. Bullock 《Proceedings. Biological sciences / The Royal Society》2015,282(1816)
Ecological intensification has been promoted as a means to achieve environmentally sustainable increases in crop yields by enhancing ecosystem functions that regulate and support production. There is, however, little direct evidence of yield benefits from ecological intensification on commercial farms growing globally important foodstuffs (grains, oilseeds and pulses). We replicated two treatments removing 3 or 8% of land at the field edge from production to create wildlife habitat in 50–60 ha patches over a 900 ha commercial arable farm in central England, and compared these to a business as usual control (no land removed). In the control fields, crop yields were reduced by as much as 38% at the field edge. Habitat creation in these lower yielding areas led to increased yield in the cropped areas of the fields, and this positive effect became more pronounced over 6 years. As a consequence, yields at the field scale were maintained—and, indeed, enhanced for some crops—despite the loss of cropland for habitat creation. These results suggested that over a 5-year crop rotation, there would be no adverse impact on overall yield in terms of monetary value or nutritional energy. This study provides a clear demonstration that wildlife-friendly management which supports ecosystem services is compatible with, and can even increase, crop yields. 相似文献