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961.
962.
"Wunder" F-BAR domains: going from pits to vesicles 总被引:1,自引:0,他引:1
Clathrin-mediated endocytosis is a key mechanism by which cells take up extracellular cargo. In this issue, Shimada et al. (2007) reveal the mode of action of the F-BAR domain, which deepens the initial membrane pit that forms during clathrin-mediated endocytosis. 相似文献
963.
Triatoma juazeirensis, a new triatomine species from the state of Bahia, Northeastern Brazil, is described. The new species is found among rocks in sylvatic environment and in the peridomicile. Type specimens were deposited in the Entomological Collection of Oswaldo Cruz Institute-Fiocruz, Museum of Zoology of University of S?o Paulo, and Florida Museum of Natural History. T. juazeirensis can be distinguished from the other members of the T. brasiliensis species complex mainly by the overall color of the pronotum, which is dark, and by the entirely dark femora. 相似文献
964.
Gabriel FL Cyris M Jonkers N Giger W Guenther K Kohler HP 《Applied and environmental microbiology》2007,73(10):3320-3326
Recently we showed that degradation of several nonylphenol isomers with alpha-quaternary carbon atoms is initiated by ipso-hydroxylation in Sphingobium xenophagum Bayram (F. L. P. Gabriel, A. Heidlberger, D. Rentsch, W. Giger, K. Guenther, and H.-P. E. Kohler, J. Biol. Chem. 280:15526-15533, 2005). Here, we demonstrate with 18O-labeling experiments that the ipso-hydroxy group was derived from molecular oxygen and that, in the major pathway for cleavage of the alkyl moiety, the resulting nonanol metabolite contained an oxygen atom originating from water and not from the ipso-hydroxy group, as was previously assumed. Our results clearly show that the alkyl cation derived from the alpha-quaternary nonylphenol 4-(1-ethyl-1,4-dimethyl-pentyl)-phenol through ipso-hydroxylation and subsequent dissociation of the 4-alkyl-4-hydroxy-cyclohexadienone intermediate preferentially combines with a molecule of water to yield the corresponding alcohol and hydroquinone. However, the metabolism of certain alpha,alpha-dimethyl-substituted nonylphenols appears to also involve a reaction of the cation with the ipso-hydroxy group to form the corresponding 4-alkoxyphenols. Growth, oxygen uptake, and 18O-labeling experiments clearly indicate that strain Bayram metabolized 4-t-butoxyphenol by ipso-hydroxylation to a hemiketal followed by spontaneous dissociation to the corresponding alcohol and p-quinone. Hydroquinone effected high oxygen uptake in assays with induced resting cells as well as in assays with cell extracts. This further corroborates the role of hydroquinone as the ring cleavage intermediate during degradation of 4-nonylphenols and 4-alkoxyphenols. 相似文献
965.
Peter J. Fashing Felix Mulindahabi Jean-Baptiste Gakima Michel Masozera Ian Mununura Andrew J. Plumptre Nga Nguyen 《International journal of primatology》2007,28(3):529-550
With group sizes sometimes >300 individuals, the Angolan black-and-white colobus (Colobus angolensis ruwenzorii) population
in Nyungwe Forest, Rwanda is an intriguing exception to the tendency for folivores to live in smaller groups than expected
relative to body size. Researchers have hypothesized that the unusually high quality of foliage at Nyungwe allows colobus
there to avoid intragroup feeding competition, releasing constraints on the formation of large groups (Fimbel et al., 2001). We collected data on the activity and ranging patterns of a >300-member Nyungwe colobus group and compared our results
to those from smaller groups in other black-and-white colobus (Colobus spp.) populations. Colobus at Nyungwe spent far more
time feeding and moving (62%) and far less time resting (32%) than black-and-white colobus at any other site. The annual home
range of the Nyungwe colobus was also many times larger (95% minimum convex polygon: 20.7 km
2
; 95% fixed kernel: 24.4 km
2
) than those for other populations. We terminated our research after the group engaged in an unprecedented migration among
black-and-white colobus by moving 13 km south of their former range. Our results suggest that intragroup scramble competition
may be more intense than originally believed within the large colobus groups at Nyungwe and that long periods of resource
renewal may be necessary after a large colobus group passes through an area, thereby potentially helping to explain their
wide ranging patterns. We discuss the socioecological convergence between the Nyungwe colobus and Chinese snub-nosed monkeys
(Rhinopithecus spp.) and suggest directions for future research on the unique black-and-white colobus population at Nyungwe.
相似文献
Peter J. FashingEmail: |
966.
Klaus S. Larsen Andreas Ibrom Claus Beier Sven Jonasson Anders Michelsen 《Biogeochemistry》2007,85(2):201-213
We measured net ecosystem CO2 flux (F
n) and ecosystem respiration (R
E), and estimated gross ecosystem photosynthesis (P
g) by difference, for two years in a temperate heath ecosystem using a chamber method. The exchange rates of carbon were high
and of similar magnitude as for productive forest ecosystems with a net ecosystem carbon gain during the second year of 293 ± 11 g C m−2 year−1 showing that the carbon sink strength of heather-dominated ecosystems may be considerable when C. vulgaris is in the building phase of its life cycle. The estimated gross ecosystem photosynthesis and ecosystem respiration from October
to March was 22% and 30% of annual flux, respectively, suggesting that both cold-season carbon gain and loss were important
in the annual carbon cycle of the ecosystem. Model fit of R
E of a classic, first-order exponential equation related to temperature (second year; R
2 = 0.65) was improved when the P
g rate was incorporated into the model (second year; R
2 = 0.79), suggesting that daytime R
E increased with increasing photosynthesis. Furthermore, the temperature sensitivity of R
E decreased from apparent Q
10 values of 3.3 to 3.9 by the classic equation to a more realistic Q
10 of 2.5 by the modified model. The model introduces R
photo, which describes the part of respiration being tightly coupled to the photosynthetic rate. It makes up 5% of the assimilated
carbon dioxide flux at 0°C and 35% at 20°C implying a high sensitivity of respiration to photosynthesis during summer. The
simple model provides an easily applied, non-intrusive tool for investigating seasonal trends in the relationship between
ecosystem carbon sequestration and respiration. 相似文献
967.
Fossil species ofMelanopsis from a freshwater formation in the Jordan Valley (near Al-Qarn) were investigated and the deposits containing these species
are formally described as Al-Qarn Formation. Four species were found:Melanopsis buccinoidea
Olivier,M. tchernovi
Heller & Sivan,M. costata
Olivier andM. aaronsohni
Blanckenhorn.Melanopsis costata was represented by two groups, “stepped” and “non-stepped”, the latter differing in its lower figurativity index. Intermediates
were found betweenM. buccinoidea andM. tchernovi; they may be hybrids. TheMelanopsis assemblage bridges the faunal gap, in the Jordan Valley, between the 2 Ma lake of ‘Erq el Ahmar on the one hand and the 0.8–1.7
Ma lake of ‘Ubeidiya on the other. This suggests an early Pleistocene age of about 1.8 million years for the Al-Qarn Formation. 相似文献
968.
969.
A plant lectin was isolated from barley (Hordeum vulgare) coleoptiles using acidic extraction and different chromatographic methods. Sequencing of more than 50% of the protein sequence
by Edman degradation confirmed a full-length cDNA clone. The subsequently identified open reading frame encodes for a 15 kDa
protein which could be found in the soluble fraction of barley coleoptiles. This protein exhibited specificity towards mannose
sugar and is therefore, accordingly named as Horcolin (Hordeum vulgare coleoptile lectin). Database searches performed with
the Horcolin protein sequence revealed a sequence and structure homology to the lectin family of jacalin-related lectins.
Together with its affinity towards mannose, Horcolin is now identified as a new member of the mannose specific subgroup of
jacalin-related lectins in monocot species. Horcolin shares a high amino acid homology to the highly light-inducible protein
HL#2 and, in addition to two methyl jasmonic acid-inducible proteins of 32.6 and 32.7 kDa where the jasmonic acid-inducible
proteins are examples of bitopic chimerolectins containing a dirigent and jacalin-related domain. Immunoblot analysis with
a cross-reactive anti-HL#2 antibody in combination with Northern blot analysis of the Horcolin cDNA revealed tissue specific
expression of Horcolin in the coleoptiles. The function of Horcolin is discussed in the context of its particular expression
in coleoptiles and is then compared to other lectins, which apparently share a related response to biotic or abiotic stress
factors. 相似文献
970.
Biedendieck R Beine R Gamer M Jordan E Buchholz K Seibel J Dijkhuizen L Malten M Jahn D 《Applied microbiology and biotechnology》2007,74(5):1062-1073
Fructosyltransferases, like the Lactobacillus reteri levansucrase, are important for the production of new fructosyloligosaccharides. Various His6- and Strep-tagged variants of this enzyme were recombinantly produced and exported into the growth medium using the Gram-positive
bacterium Bacillus megaterium. Nutrient-rich growth medium significantly enhanced levansucrase production and export. The B. megaterium signal peptide of the extracellular esterase LipA mediated better levansucrase export compared to the one of the penicillin
amidase Pac. The combination of protein export via the LipA signal peptide with the coexpression of the signal peptidase gene
sipM further increased the levansucrase secretion. Fused affinity tags allowed the efficient one-step purification of the recombinant
proteins from the growth medium. However, fused peptide tags led to slightly decreased secretion of tested fusion proteins.
After upscaling 2 to 3 mg affinity tagged levansucrase per liter culture medium was produced and exported. Up to 1 mg of His6-tagged and 0.7 mg of Strep-tagged levansucrase per liter were recovered by affinity chromatography. Finally, the purified
levansucrase was shown to synthesize new fructosyloligosaccharides from the novel donor substrates d-Gal-Fru, d-Xyl-Fru, d-Man-Fru, and d-Fuc-Fru.
R. Biedendieck and R. Beine contributed equally to this work. 相似文献