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991.
The disappearance of spawned copepod eggs can, at times, approach100% day1 and may be a bottleneck to population recruitmentof marine copepods. We examined the egg production rate andegg hatching success of Centropages hamatus and Temora longicomis(Copepoda: Calanoida) on natural diets, and the role of delayedhatching combined with high sinking rates in removing theireggs from the water column. Cumulative hatching success withinIS days was consistently high from March to June 1996: 相似文献
992.
Michaël H. Kolk Sybren S. Wijmenga Hans A. Heus Cornelis W. Hilbers 《Journal of biomolecular NMR》1998,12(3):423-433
The complete T- and pseudoknotted acceptor arm of the tRNA-like structure of turnip yellow mosaic virus (TYMV) genomic RNA has been studied by NMR spectroscopy. Resonance assignment and the gathering of restraints of the 44-mer are impeded by spectral complexity as well as by line broadening. The latter is caused by local dynamical effects in the pseudoknot domain in the molecule. These specific problems could be solved by using different field strengths and selectively 13C/15 labeled samples. Experiments for assigning the sugar spin systems were adjusted to satisfy the requirements of this system. Furthermore, the quality of the structure could be improved by determining the backbone torsion angles , and , using new approaches that were tailored for use in large RNA molecules. 相似文献
993.
Patrik Andersson Bernard Gsell Beat Wipf Hans Senn Gottfried Otting 《Journal of biomolecular NMR》1998,11(3):279-288
An HMQC experiment is proposed, dubbed FHMQC, where water flip-back is achieved by a single water-selective pulse preceding the basic HMQC pulse sequence. The scheme is demonstrated with a 15N, 1H-HMQC spectrum of uniformly 15N/2H-labelled S. aureus DNA gyrase B with a molecular weight of 45 kDa for the unlabelled protein. The sensitivity of the experiment is improved compared to that of an FHSQC spectrum. It is further shown that the original FHSQC experiment can be shortened by the use of bipolar gradients. Relaxation times of different 15N magnetizations and coherences were measured. The new FHMQC scheme is implemented in 3D NOESY-15N-HMQC and 3D15 N-HMQC-NOESY-15N-HMQC pulse sequences which are demonstrated with a 24 kDa fragment of uniformly 15N/13C/2H-labelled S. aureus DNA gyrase B. 相似文献
994.
Hans Ulrich Stilz Wolfgang Guba Bernd Jablonka Melitta Just Otmar Klingler Wolfgang König Volkmar Wehner Gerhard Zoller 《Letters in Peptide Science》1998,5(2-3):215-221
Antagonists of the platelet fibrinogen receptor (GP IIb/IIIa receptor) are expected to be a new promising class of antithrombotic agents. The binding of fibrinogen to the fibrinogen receptor depends on an Arg-Gly-Asp-Ser (RGDS) tetrapeptide recognition motif. Structural modifications of the RGDS lead have led to the discovery of a non-peptide RGD mimetic GP IIb/IIIa antagonist 20 (S 1197). Compound 20 inhibits dose-dependently and reversibly human platelet aggregation. Modeling studies based on structure–activity data revealed the following structural features of the drug as important for receptor binding: the amidino group, the carboxylate group, hydrophobic substitutions at the carboxyl-terminus and at the side chain carrying the positive charge, the carboxyl-terminal NH group of the -amino acid as a hydrogen bond donor and one oxygen atom of the hydantoin as a hydrogen bond acceptor. The ethyl ester prodrug of 20 (S 5740) is an orally active antithrombotic agent which has the potential to be used to treat and prevent thrombotic diseases in humans. 相似文献
995.
Leonard C. Schalkwyk Michael Weiher Michelle Kirby Brian Cusack Heinz Himmelbauer Hans Lehrach 《Mammalian genome》1998,9(10):807-811
We have made a radiation hybrid map of mouse Chromosome (Chr) 17 with 75 microsatellite markers, including those from McCarthy
et al. (Genome Res 7, 1153–1161, 1997). Seventy-four of the markers are linked at LOD > 9, and all link at LOD > 5. A LOD
3 framework of 18 markers was used to construct a placement map. The order obtained is in good agreement with genetic maps,
and distance estimates give an idea of how recombination rates vary across the chromosome. Recombination is remarkably low
with respect to RH break frequency in the region from the centromere to the end of H2. This is similar in interspecific and
intersubspecific crosses despite the inversion of a substantial part of this region in Mus spretus with respect to Mus musculus.
Received: 10 April 1998 / Accepted: 18 June 1998 相似文献
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999.
Hans Ter Steege 《Biodiversity and Conservation》1998,7(11):1457-1483
Forest inventories are largely neglected in the debate of national parks selection in Guyana (and probably elsewhere). Because taxonomic data are often scant and biased towards are as of high collecting effort, large scale forest inventory data can be a useful tool adding to a knowledge database for forests. In this paper the use of forest inventories to select national parks in Guyana is assessed. With the data of a large scale inventory five forest regions could be distinguished and two were added on the base of existing other information. Forest composition in Guyana is largely determined by geology at a national level and soil type at regional level. Species diversity is higher in the south of Guyana, possibly due to higher disturbance and is also higher on the better soils. It is concluded that a selection of national parks in Guyana should include a sample of all seven regions, including as much soil variation as possible. Because of land use conflicts in central Guyana, this area is in need of quick attention of Guyana's policy makers. 相似文献
1000.
Teresa Mozo Sabine Fischer Sebastian Meier-Ewert Hans Lehrach Thomas Altmann 《The Plant journal : for cell and molecular biology》1998,16(3):377-384
In order to generate a physical map of the Arabidopsis thaliana genome based on bacterial artificial chromosome clones (BACs), an iterative high throughput hybridisation strategy was applied and its efficiency was evaluated. Thus, probes generated from both ends of 500 BAC clones selected from the Arabidopsis –IGF–BAC library were hybridised to the entire library gridded on high density filters. The 1000 hybridisation reactions identified 4496 clones (41.8% of the complete library, or 50.3% if organellar, centromeric, and ribosomal DNA carrying clones are excluded) which were assembled into a minimum of 220 contigs. These results demonstrate the viability of the applied ‘double-end clone-limited/sampling without replacement’ hybridisation strategy for the generation of a high resolution physical map, and provide a highly useful resource for map-based gene cloning approaches and further genome analysis. 相似文献