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51.
Mbikay M Croissandeau G Sirois F Anini Y Mayne J Seidah NG Chrétien M 《Developmental biology》2007,306(2):584-598
52.
Summary N-Boc protected non-proteinogenic dipeptides with D,L-and L,L-configuration were prepared by catalytic asymmetric hydrogenation of the corresponding dehydrophenylalanyl-(L)-phenylalanine derivatives. The configuration of the new stereogenic centre depends first of all on the catalyst configuration and is less influenced by the substrate configuration. Diastereomeric excesses in the range of 80–96% de could be increased up to 99% by recrystallization. Analytical data of selected new compounds are given.Abbreviations PINDOPHOS
2,3-O,N-bis(diphenylphosphino)-1-(4-indolyloxy)-2-hydroxy-3-isopropylamino propane
- PROPRAPHOS
2,3-O,N-bis(diphenylphosphino)-1-(naphthoxy)-2-hydroxy-3-isopropylamino propane
- BDPB
1,4-bis(diphenylphosphino)butane 相似文献
53.
Zhong M Munzer JS Basak A Benjannet S Mowla SJ Decroly E Chrétien M Seidah NG 《The Journal of biological chemistry》1999,274(48):33913-33920
All proprotein convertases (PCs) of the subtilisin/kexin family contain an N-terminal prosegment that is presumed to act both as an intramolecular chaperone and an inhibitor of its parent enzyme. In this work, we examined inhibition by purified, recombinant bacterial prosegments of furin and PC7 on the in vitro processing of either the fluorogenic peptide pERTKR-MCA or the human immunodeficiency virus envelope glycoprotein gp160. These propeptides are potent inhibitors that display measurable selectivity toward specific proprotein convertases. Small, synthetic decapeptides derived from the C termini of the prosegments are also potent inhibitors, albeit less so than the full-length proteins, and the C-terminal P1 arginine is essential for inhibition. The bacterial, recombinant prosegments were also used to generate specific antisera, allowing us to study the intracellular metabolic fate of the prosegments of furin and PC7 expressed via vaccinia virus constructs. These vaccinia virus recombinants, along with transient transfectants of the preprosegments of furin and PC7, efficiently inhibited the ex vivo processing of the neurotrophins nerve growth factor and brain-derived neurotrophic factor. Thus, we have demonstrated for the first time that PC prosegments, expressed ex vivo as independent domains, can act in trans to inhibit precursor maturation by intracellular PCs. 相似文献
54.
BACKGROUND: CLIP-170 is a microtubule binding protein specifically located at microtubule plus ends, where it modulates their dynamic properties and their interactions with intracellular organelles. The mechanism by which CLIP-170 is targeted to microtubule ends remains unclear today, as well as its precise effect on microtubule dynamics. RESULTS: We used the N-terminal part of CLIP-170 (named H2), which contains the microtubule binding domains, to investigate how it modulates in vitro microtubule dynamics and structure. We found that H2 primarily promoted rescues (transitions from shrinkage to growth) of microtubules nucleated from pure tubulin and isolated centrosomes, and stimulated microtubule nucleation. Electron cryomicroscopy revealed that H2 induced the formation of tubulin rings in solution and curved oligomers at the extremities of microtubules in assembly conditions. CONCLUSIONS: These results suggest that CLIP-170 targets specifically at microtubule plus ends by copolymerizing with tubulin and modulates microtubule nucleation, polymerization, and rescues by the same basic mechanism with tubulin oligomers as intermediates. 相似文献
55.
Based on exact numerical simulations, taking into account isotropic and conformation-dependent anisotropic nuclear spin interactions, we systematically analyse the prospects for high-resolution solid-state NMR on large isotope-labeled membrane proteins macroscopically oriented in phospholipid bilayers. Using the known X-ray structures of rhodopsin and porin as models for large membrane proteins with typical -helical and -barrel structural motifs, the analysis considers all possible one- to six-dimensional spectra comprised of frequency dimensions with evolution under any combination of amide 1H, amide 15N, and carbonyl 13C chemical shifts as well as 1H-15N dipole-dipole couplings. Under consideration of typical nuclear spin interaction and experimental line-shape parameters, the analysis provides new insight into the resolution capability and orientation-dependent transfer efficiency of existing experiments as well as guidelines as to improved experimental approaches for the study of large uniformly 15N- and [13C,15N]-labeled membrane proteins. On basis of these results and numerical optimizations of coherence-transfer efficiencies, we propose several new high-resolution experiments for sequential protein backbone assignment and structure determination. 相似文献
56.
Dynamic effects of predators on cyclic voles: field experimentation and model extrapolation 总被引:9,自引:0,他引:9
Korpimäki E Norrdahl K Klemola T Pettersen T Stenseth NC 《Proceedings. Biological sciences / The Royal Society》2002,269(1495):991-997
Mechanisms generating the well-known 3-5 year cyclic fluctuations in densities of northern small rodents (voles and lemmings) have remained an ecological puzzle for decades. The hypothesis that these fluctuations are caused by delayed density-dependent impacts of predators was tested by replicated field experimentation in western Finland. We reduced densities of all main mammalian and avian predators through a 3 year vole cycle and compared vole abundances between four reduction and four control areas (each 2.5-3 km(2)). The reduction of predator densities increased the autumn density of voles fourfold in the low phase, accelerated the increase twofold, increased the autumn density of voles twofold in the peak phase, and retarded the initiation of decline of the vole cycle. Extrapolating these experimental results to their expected long-term dynamic effects through a demographic model produces changes from regular multiannual cycles to annual fluctuations with declining densities of specialist predators. This supports the findings of the field experiment and is in agreement with the predation hypothesis. We conclude that predators may indeed generate the cyclic population fluctuations of voles observed in northern Europe. 相似文献
57.
Biessen EA Sliedregt-Bol K 'T Hoen PA Prince P Van der Bilt E Valentijn AR Meeuwenoord NJ Princen H Bijsterbosch MK Van der Marel GA Van Boom JH Van Berkel TJ 《Bioconjugate chemistry》2002,13(2):295-302
In this study, we present the design and synthesis of an antisense peptide nucleic acid (asPNA) prodrug, which displays an improved biodistribution profile and an equally improved capacity to reduce the levels of target mRNA. The prodrug, K(GalNAc)(2)-asPNA, comprised of a 14-mer sequence complementary to the human microsomal triglyceride transfer protein (huMTP) gene, conjugated to a high-affinity tag for the hepatic asialoglycoprotein receptor (K(GalNAc)(2)). The prodrug was avidly bound and rapidly internalized by HepG2s. After iv injection into mice, K(GalNAc)(2)-asPNA accumulated in the parenchymal liver cells to a much greater extent than nonconjugated PNA (46% +/- 1% vs 3.1% +/- 0.5% of the injected dose, respectively). The prodrug was able to reduce MTP mRNA levels in HepG2 cells by 35-40% (P < 0.02) at 100 nM in an asialoglycoprotein receptor- and sequence-dependent fashion. In conclusion, hepatocyte-targeted PNA prodrugs combine a greatly improved tropism with an enhanced local intracellular availability and activity, making them attractive therapeutics to lower the expression level of hepatic target genes such as MTP. 相似文献
58.
J. Chr Vogel S. J. Russell F. J. Rumsey J. A. Barrett Mary Gibby 《Plant biology (Stuttgart, Germany)》1998,111(3):241-246
Length polymorphism in a non-coding spacer (trnLUAA-trnFGAA) in the chloroplast DNA was used in the investigation of the origin of the most common and conspicuous European fern hybrid, Asplenium x alternifolium (Aspleniaceae, Pteridophyta). The origins of A. x alternifolium, the hybrid between A. trichomanes s.l. and A. septentrionale s.l. was studied at three ploidy levels, diploid, triploid and tetraploid. The cpDNA technique allowed us to investigate the mode of hybrid formation between sexual species for the first time over a wide geographic range and with a large sample size. Morphological variation in this hybrid has previously been attributed to different reciprocal parental combinations, and to the influence of chloroplast genes on morphogenesis. Our results demonstrate that one parent, A. septentrionale s.l., acts predominantly as the female parent in these hybrids, with only one population of A. x alternifolium showing reciprocal hybridity. The discovery of predominantly unidirectional hybrid formation in this hybrid may be explained by the different breeding systems of the parental taxa. The role of gametophyte ecology is also assessed. 相似文献
59.
M. REICHSTEIN P. CIAIS D. PAPALE R. VALENTINI S. RUNNING N. VIOVY W. CRAMER A. GRANIER J. OGE V. ALLARD M. AUBINET Chr. BERNHOFER N. BUCHMANN A. CARRARA T. GRÜNWALD M. HEIMANN B. HEINESCH A. KNOHL W. KUTSCH D. LOUSTAU G. MANCA G. MATTEUCCI F. MIGLIETTA J.M. OURCIVAL K. PILEGAARD J. PUMPANEN S. RAMBAL S. SCHAPHOFF G. SEUFERT J.‐F. SOUSSANA M.‐J. SANZ T. VESALA M. ZHAO 《Global Change Biology》2007,13(3):634-651
The European CARBOEUROPE/FLUXNET monitoring sites, spatial remote sensing observations via the EOS‐MODIS sensor and ecosystem modelling provide independent and complementary views on the effect of the 2003 heatwave on the European biosphere's productivity and carbon balance. In our analysis, these data streams consistently demonstrate a strong negative anomaly of the primary productivity during the summer of 2003. FLUXNET eddy‐covariance data indicate that the drop in productivity was not primarily caused by high temperatures (‘heat stress’) but rather by limitation of water (drought stress) and that, contrary to the classical expectation about a heat wave, not only gross primary productivity but also ecosystem respiration declined by up to more than to 80 gC m−2 month−1. Anomalies of carbon and water fluxes were strongly correlated. While there are large between‐site differences in water‐use efficiency (WUE, 1–6 kg C kg−1 H2O) here defined as gross carbon uptake divided by evapotranspiration (WUE=GPP/ET), the year‐to‐year changes in WUE were small (<1 g kg−1) and quite similar for most sites (i.e. WUE decreased during the year of the heatwave). Remote sensing data from MODIS and AVHRR both indicate a strong negative anomaly of the fraction of absorbed photosynthetically active radiation in summer 2003, at more than five standard deviations of the previous years. The spatial differentiation of this anomaly follows climatic and land‐use patterns: Largest anomalies occur in the centre of the meteorological anomaly (central Western Europe) and in areas dominated by crops or grassland. A preliminary model intercomparison along a gradient from data‐oriented models to process‐oriented models indicates that all approaches are similarly describing the spatial pattern of ecosystem sensitivity to the climatic 2003 event with major exceptions in the Alps and parts of Eastern Europe, but differed with respect to their interannual variability. 相似文献
60.
Thomas R. Wittenborn Esben K.U. Larsen Thomas Nielsen Louise M. Rydtoft Line Hansen Jens V. Nygaard Thomas Vorup-Jensen Jørgen Kjems Michael R. Horsman Niels Chr. Nielsen 《Biochemical and biophysical research communications》2014