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991.
Seasonal nutrient and plankton dynamics in a physical-biological model of Crater Lake 总被引:1,自引:1,他引:0
Katja Fennel Robert Collier Gary Larson Greg Crawford Emmanuel Boss 《Hydrobiologia》2007,574(1):265-280
A coupled 1D physical-biological model of Crater Lake is presented. The model simulates the seasonal evolution of two functional
phytoplankton groups, total chlorophyll, and zooplankton in good quantitative agreement with observations from a 10-year monitoring
study. During the stratified period in summer and early fall the model displays a marked vertical structure: the phytoplankton
biomass of the functional group 1, which represents diatoms and dinoflagellates, has its highest concentration in the upper
40 m; the phytoplankton biomass of group 2, which represents chlorophyta, chrysophyta, cryptomonads and cyanobacteria, has
its highest concentrations between 50 and 80 m, and phytoplankton chlorophyll has its maximum at 120 m depth. A similar vertical
structure is a reoccurring feature in the available data. In the model the key process allowing a vertical separation between
biomass and chlorophyll is photoacclimation. Vertical light attenuation (i.e., water clarity) and the physiological ability
of phytoplankton to increase their cellular chlorophyll-to-biomass ratio are ultimately determining the location of the chlorophyll
maximum. The location of the particle maxima on the other hand is determined by the balance between growth and losses and
occurs where growth and losses equal. The vertical particle flux simulated by our model agrees well with flux measurements
from a sediment trap. This motivated us to revisit a previously published study by Dymond et al. (1996). Dymond et al. used a box model to estimate the vertical particle flux and found a discrepancy by a factor 2.5–10 between
their model-derived flux and measured fluxes from a sediment trap. Their box model neglected the exchange flux of dissolved
and suspended organic matter, which, as our model and available data suggests is significant for the vertical exchange of
nitrogen. Adjustment of Dymond et al.’s assumptions to account for dissolved and suspended nitrogen yields a flux estimate
that is consistent with sediment trap measurements and our model. 相似文献
992.
Zogopoulos G Ha KC Naqib F Moore S Kim H Montpetit A Robidoux F Laflamme P Cotterchio M Greenwood C Scherer SW Zanke B Hudson TJ Bader GD Gallinger S 《Human genetics》2007,122(3-4):345-353
Genomic copy number variation (CNV) is a recently identified form of global genetic variation in the human genome. The Affymetrix
GeneChip 100 and 500 K SNP genotyping platforms were used to perform a large-scale population-based study of CNV frequency.
We constructed a genomic map of 578 CNV regions, covering approximately 220 Mb (7.3%) of the human genome, identifying 183
previously unknown intervals. Copy number changes were observed to occur infrequently (<1%) in the majority (>93%) of these
genomic regions, but encompass hundreds of genes and disease loci. This North American population-based map will be a useful
resource for future genetic studies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
993.
Stiff CM Zhong M Sarver RW Gao H Ho AM Sweeney MT Zurenko GE Romero DL 《Bioorganic & medicinal chemistry letters》2007,17(19):5479-5482
Previously we reported the discovery and initial optimization of a novel anthranilic acid derived class of antibacterial agents which suffered from extensive protein binding. This report describes efforts directed toward understanding the relationship of the acidity of the carboxylic acid with the extent of protein binding. The pK(a) of the acid was modified via the synthesis of a number of anthranilic acid analogs which vary the aromatic ring substituent at the 4-position. The pK(a) and HSA binding constants have been determined for each of the analogs. Our results indicate a correlation between pK(a) and HSA K(d). The physical properties and antibacterial activities will be discussed as well as how these results help address the protein binding issue with this series of compounds. 相似文献
994.
Feng Z Mohapatra S Klimko PG Hellberg MR May JA Kelly C Williams G McLaughlin MA Sharif NA 《Bioorganic & medicinal chemistry letters》2007,17(11):2998-3002
A series of 8-substituted benzodifuran analogs was prepared and evaluated for 5-HT(2A) receptor binding and activation. Several compounds containing ether and ester functionality were found to be potent agonists. Topical ocular administration of 5, 18, and 25 effectively reduced intra-ocular pressure in the hypertensive cynomolgus monkey eye in the range of 25-37%. 相似文献
995.
A whole-genome RNAi Screen for C. elegans miRNA pathway genes 总被引:1,自引:0,他引:1
BACKGROUND: miRNAs are an abundant class of small, endogenous regulatory RNAs. Although it is now appreciated that miRNAs are involved in a broad range of biological processes, relatively little is known about the actual mechanism by which miRNAs downregulate target gene expression. An exploration of which protein cofactors are necessary for a miRNA to downregulate a target gene should reveal more fully the molecular mechanisms by which miRNAs are processed, trafficked, and regulate their target genes. RESULTS: A weak allele of the C. elegans miRNA gene let-7 was used as a sensitized genetic background for a whole-genome RNAi screen to detect miRNA pathway genes, and 213 candidate miRNA pathway genes were identified. About 2/3 of the 61 candidates with the strongest phenotype were validated through genetic tests examining the dependence of the let-7 phenotype on target genes known to function in the let-7 pathway. Biochemical tests for let-7 miRNA production place the function of nearly all of these new miRNA pathway genes downstream of let-7 expression and processing. By monitoring the downregulation of the protein product of the lin-14 mRNA, which is the target of the lin-4 miRNA, we have identified 19 general miRNA pathway genes. CONCLUSIONS: The 213 candidate miRNA pathway genes identified could act at steps that produce and traffic miRNAs or in downstream steps that detect miRNA::mRNA duplexes to regulate mRNA translation. The 19 validated general miRNA pathway genes are good candidates for genes that may define protein cofactors for sorting or targeting miRNA::mRNA duplexes, or for recognizing the miRNA base-paired to the target mRNA to downregulate translation. 相似文献
996.
Zheng QH Gao M Mock BH Wang S Hara T Nazih R Miller MA Receveur TJ Lopshire JC Groh WJ Zipes DP Hutchins GD DeGrado TR 《Bioorganic & medicinal chemistry letters》2007,17(8):2220-2224
The high-affinity choline transporter (CHT1) system is an attractive target for the development of positron emission tomography (PET) biomarkers to probe brain, cardiac, and cancer diseases. An efficient and convenient synthesis of new radiolabeled CHT1 inhibitors [(11)C]hemicholinium-3 and [(18)F]hemicholinium-3 by solid-phase extraction (SPE) technique using a cation-exchange CM Sep-Pak cartridge has been well developed. The preliminary evaluation of both tracers through biodistribution studies in 9L-glioma rats has been performed, and the uptakes in the heart and tumor were observed, while very low brain uptake was seen. 相似文献
997.
Abu-Baker S Lu JX Chu S Shetty KK Gor'kov PL Lorigan GA 《Protein science : a publication of the Protein Society》2007,16(11):2345-2349
For the first time, 15N solid-state NMR experiments were conducted on wild-type phospholamban (WT-PLB) embedded inside mechanically oriented phospholipid bilayers to investigate the topology of its cytoplasmic and transmembrane domains. 15N solid-state NMR spectra of site-specific 15N-labeled WT-PLB indicate that the transmembrane domain has a tilt angle of 13 degrees+/-6 degrees with respect to the POPC (1-palmitoyl-2-oleoyl-sn-glycero-phosphocholine) bilayer normal and that the cytoplasmic domain of WT-PLB lies on the surface of the phospholipid bilayers. Comparable results were obtained from site-specific 15N-labeled WT-PLB embedded inside DOPC/DOPE (1,2-dioleoyl-sn-glycero-3-phosphocholine/1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) mechanically oriented phospholipids' bilayers. The new NMR data support a pinwheel geometry of WT-PLB, but disagree with a bellflower structure in micelles, and indicate that the orientation of the cytoplasmic domain of the WT-PLB is similar to that reported for the monomeric AFA-PLB mutant. 相似文献
998.
Mating trials validate the use of DNA barcoding to reveal cryptic speciation of a marine bryozoan taxon 总被引:3,自引:0,他引:3
Gómez A Wright PJ Lunt DH Cancino JM Carvalho GR Hughes RN 《Proceedings. Biological sciences / The Royal Society》2007,274(1607):199-207
Despite increasing threats to the marine environment, only a fraction of the biodiversity of the oceans has been described, owing in part to the widespread occurrence of cryptic species. DNA-based barcoding through screening of an orthologous reference gene has been proposed as a powerful tool to uncover biological diversity in the face of dwindling taxonomic expertise and the limitations of traditional species identification. Although DNA barcoding should be particularly useful in the sea, given the prevalence of marine cryptic species, the link between taxa identified through DNA barcodes and reproductively isolated taxa (biological species) has rarely been explicitly tested. Here, we use an integrated framework comparing breeding compatibility, morphology and mitochondrial (cytochrome c oxidase 1) and nuclear (elongation factor-1-alpha) DNA sequence variation among globally distributed samples of the cosmopolitan marine bryozoan Celleporella hyalina (L.). Our results reveal that C. hyalina comprises numerous deep, mostly allopatric, genetic lineages that are reproductively isolated, yet share very similar morphology, indicating rampant cryptic speciation. The close correspondence between genetic lineages and reproductively isolated taxa in the context of minimal morphological change suggests that DNA barcoding will play a leading role in uncovering the hidden biodiversity of the oceans and that the sole use of morphologically based taxonomy would grossly underestimate the number of marine species. 相似文献
999.
Molecularly imprinted polymer films for reflectometric interference spectroscopic sensors 总被引:2,自引:0,他引:2
Belmont AS Jaeger S Knopp D Niessner R Gauglitz G Haupt K 《Biosensors & bioelectronics》2007,22(12):3267-3272
Reflectometric interference spectroscopic measurements were performed on molecularly imprinted polymer (MIP) films with the herbicide atrazine as the template molecule. A conventional imprinting protocol was used relying on non-covalent interactions between the functional monomers and the template. The MIPs were deposited on glass transducers by two different methods: spin-coating followed by in situ polymerization of thin films of monomers containing a sacrificial polymeric porogen, and autoassembly of MIP nanoparticles with the aid of an associative linear polymer. Reproducible results were obtained upon measurements of atrazine solutions in toluene with both films. Atrazine concentrations as low as 1.7 ppm could be detected with the autoassembled particle film. No or very little analyte adsorption was observed onto non-imprinted control films made by spin-coating and by particle assembly, respectively. We believe that these MIP layers in combination with the general reflectrometric transduction scheme could be a versatile sensing tool for the detection of environmentally important and other analytes. 相似文献
1000.
Difluoromethyl analogs of the natural hormone 1alpha,25-dihydroxyvitamin D3: Design, synthesis, and preliminary biological evaluation 总被引:1,自引:0,他引:1