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  • Articles: DFG German National Licenses  (17)
  • Chemistry  (12)
  • root  (3)
  • Dissociation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Use of the maize transposonsActivator andDissociation to show that phosphinothricin and spectinomycin resistance genes act non-cell-autonomously in tobacco and tomato seedlings (1993)
    Springer
    Transgenic research 2 (1993), S. 63-78 
    Details
    ISSN: 1573-9368
    Keywords: transposon ; Activator ; Dissociation ; cell-autonomous ; spectinomycin ; tomato ; phosphinothricin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cell-autonomous genes have been used to monitor the excision of both endogenous transposons in maize andAntirrhinum, and transposons introduced into transgenic plants. In tobacco andArabidopsis, the streptomycin phosphotransferase (SPT) gene reveals somatic excision of the maize transposonActivator (Ac) as green sectors on a white background in cotyledons of seedlings germinated in the presence of streptomycin. Cotyledons of tomato seedlings germinated on streptomycin-containing medium do not bleach, suggesting that a different assay for transposon excision in tomato is desirable. We have tested the use of the spectinomycin resistance (SPEC) gene (aadA) and a Basta resistance (BAR) gene (phosphinothricin acetyltransferase, or PAT) for monitoring somatic excision ofAc in tobacco and tomato. Both genetic and molecular studies demonstrate that genotypically variegated individuals that carry clones of cells from whichAc orDs have excised from either SPEC or BAR genes, can be phenotypically completely resistant to the corresponding antibiotic. This demonstrates that these genes act non-cell-autonomously, in contrast to the SPT gene in tobacco. Possible reasons for this difference are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01969379
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  • 2
    Electronic Resource
    Electronic Resource
    Chloroplast targeting of spectinomycin adenyltransferase provides a cell-autonomous marker for monitoring transposon excision in tomato and tobacco (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 189-196 
    Details
    ISSN: 1617-4623
    Keywords: Tomato ; Tobacco ; Transposon tagging ; Activator ; Dissociation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antibiotic resistance genes can act as either cell autonomous or non-cell autonomous genetic markers with which to monitor the excision of plant transposons. To convert spectinomycin resistance from a noncell autonomous resistance to cell autonomous resistance, a transit peptide for chloroplast localization from a petunia ribulose bisphosphate carboxylase (rbcS) gene was fused in-frame to the aadA gene, which confers spectinomycin and streptomycin resistance. Constructs were generated in which the expression of this chimeric gene was prevented by the presence, in the 5′ untranslated leader, of the maize transposons Activator (Ac) or Dissociation (Ds). When progeny of tobacco or tomato plants transformed with these constructs were germinated on spectinomycin-containing medium, germinally revertant and somatically variegated individuals could be distinguished.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283522
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  • 3
    Electronic Resource
    Electronic Resource
    Influx and efflux of organic acids across the soil-root interface of Zea mays L. and its implications in rhizosphere C flow (1995)
    Springer
    Plant and soil 173 (1995), S. 103-109 
    Details
    ISSN: 1573-5036
    Keywords: maize ; organic acids ; rhizosphere ; root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influx and efflux of organic acids across the root-soil interface were investigated in intact, sterile maize (Zea mays L.) roots under a variety of experimental conditions. Under nutrient-sufficient conditions the efflux of organic acids was shown to constitute 〈 1% of the total C lost across the root-soil interface. Under severe nutrient stress, however, the rates of malate and citrate efflux from the root increased 33 and 12 fold respectively. Influx experiments indicated that roots could not directly reabsorb citrate-Fe3+ or other metal complexes from solution. Influx of citrate was observed only at high external citrate concentration (≥ 1 mM) or from solutions with low ionic strengths. It was postulated that citrate influx is of little importance in a soil environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155523
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  • 4
    Electronic Resource
    Electronic Resource
    Critical evaluation of organic acid mediated iron dissolution in the rhizosphere and its potential role in root iron uptake (1996)
    Springer
    Plant and soil 180 (1996), S. 57-66 
    Details
    ISSN: 1573-5036
    Keywords: citrate ; iron ; organic acids ; rhizosphere ; root
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Both experimental extractions and theoretical calculations were undertaken to assess whether organic acid-mediated Fe dissolution could play a significant role in elevating the concentration of Fe-complexes in the rhizosphere, and further, whether this could satisfy the Fe demands of a plant utilizing ferric reduction to acquire Fe. Using a mathematical computer model, it was predicted that organic acids released from and diffusing away from the root would result in a solution organic acid concentration at the root surface of between 1 to 50 μM. Over 99% of the organic acids lost by the root were predicted to remain within 1 mm of the root surface. The experimental results indicated that citrate-mediated Fe dissolution of amorphous Fe(OH)3, was rapid in comparison with citrate dissolution of the Fe-oxides, Fe2O3 and Fe3O4. The rate of citrate and malate mediated Fe-dissolution was dependent on many factors such as pH, metal cations and phosphate saturation of the Fe(OH)3 surface. At pH values ≤6.8, citrate formed stable complexes with Fe and dissolution proceeded rapidly. Under optimal growth conditions for a plant utilizing a reductive-bound mechanism of Fe acquisition (dicots and non-grass monocots), it can be expected that citrate and malate may be able to satisfy a significant proportion of the plant's Fe demand through the formation of plant-available organic-Fe3+ complexes in the rhizosphere. In high pH soils (pH≥7.0), the plant must rely on other sources of Fe, as citrate-mediated Fe dissolution is slow and Fe-citrate complexes are unstable. Alternatively, the root acidification of the rhizosphere could allow the formation of stable Fe-organic complexes. ei]H Marschner
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015411
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  • 5
    Electronic Resource
    Electronic Resource
    Re-sorption of organic compounds by roots of Zea mays L. and its consequences in the rhizosphere (1996)
    Springer
    Plant and soil 178 (1996), S. 153-160 
    Details
    ISSN: 1573-5036
    Keywords: carbon flow ; maize ; rhizosphere ; root ; sugar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influx and efflux of sugar-C and the cycling of C within intact maize roots (Zea mays L.) was studied in sterile solution culture. Using metabolic inhibitors it was shown that roots could take up sugars against the concentration gradient probably via H+-ATPase dependent plasmalemma proton cotransporters. In contrast to this, no evidence was found for an ATPase mediated efflux of sugars from the root. All parts of the root were capable of taking up exogenous sugars. Examination of sugar exudation sites along the root slowed efflux at all locations, with the amount of efflux linearly correlated with internal cellular concentration. The results clearly indicated that the influxefflux mechanisms are linked both spatially, temporally and with respect to the sugars capable of transportation. The turnover of C within the root was found to be extremely rapid with turnover of the soluble sugar pool being 0.8 to 15 times daily depending on root spatial location. The results strongly suggest that the recapture of sugars from outside the root plays an important role in regulating the amount of C lost to the soil which in turn will reduce both pathogen attraction and the size of the rhizosphere microbial population and will also increase the plant's C efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00011173
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  • 6
    Electronic Resource
    Electronic Resource
    Design and synthesis of nonpeptide peptidomimetic inhibitors of renin (1995)
    New York : Wiley-Blackwell
    Biopolymers 37 (1995), S. 29-53 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The desire to replace the amide backbone of renin inhibitors with a new scaffold led us to explore vinylogous amides (enaminones). An initial attempt proved unsuccessful, a result explained after the fact via docking experiments. Based on this lesson, we designed a different vinylogous amide scaffold which incorportated one or more pyrrolinone rings into the backbone. Three of the four compounds gave IC50s in the 0.6 to 18 μM range. These compounds did not inhibit HIV-1 protease. Taken together, the results reported herein provide insights into the role of hydrogen bonding and steric interactions for binding to renin. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360370106
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  • 7
    Electronic Resource
    Electronic Resource
    A method for α-helical integral membrane protein fold prediction (1994)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 18 (1994), S. 281-294 
    Details
    ISSN: 0887-3585
    Keywords: membrane ; protein ; structure ; prediction ; G-protein coupled receptor ; rhodopsin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Integral membrane proteins (of the α-helical class) are of central importance in a wide variety of vital cellular functions. Despite considerable effort on methods to predict the location of the helices, little attention has been directed toward developing an automatic method to pack the helices together. In principle, the prediction of membrane proteins should be easier than the prediction of globular proteins: there is only one type of secondary structure and all helices pack with a common alignment across the membrane. This allows all possible structures to be represented on a simple lattice and exhaustively enumerated. Prediction success lies not in generating many possible folds but in recognizing which corresponds to the native. Our evaluation of each fold is based on how well the exposed surface predicted from a multiple sequence alignment fits its allocated position. Just as exposure to solvent in globular proteins can be predicted from sequence variation, so exposure to lipid can be recognized by variable-hydrophobic (variphobic) positions. Application to both bacteriorhodopsin and the eukaryotic rhodopsin/opsin families revealed that the angular size of the lipid-exposed faces must be predicted accurately to allow selection of the correct fold. With the inherent uncertainties in helix prediction and parameter choice, this accuracy could not be guaranteed but the correct fold was typically found in the top six candidates. Our method provides the first completely automatic method that can proceed from a scan of the protein sequence databanks to a predicted three-dimensional structure with no intervention required from the investigator. Within the limited domain of the seven helix bundle proteins, a good chance can be given of selecting the correct structure. However, the limited number of sequences available with a corresponding known structure makes further characterization of the method difficult. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340180309
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  • 8
    Electronic Resource
    Electronic Resource
    Towards meeting the paracelsus challenge: The design, synthesis, and characterization of paracelsin-43, an α-helical protein with over 50% sequence identity to an all-β protein (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 502-513 
    Details
    ISSN: 0887-3585
    Keywords: de novo design ; protein structure ; inverse folding ; genetic algorithms ; 1H NMR ; CD ; peptide ; protein folding ; methanol ; ethylene glycol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In response to the Paracelsus Challenge (Rose and Creamer, Proteins, 19:1-3, 1994), we present here the design, synthesis, and characterization of a helical protein, whose sequence is 50% identical to that of an all-β protein. The new sequence was derived by applying an inverse protein folding approach, in which the sequence was optimized to “fit” the new helical structure, but constrained to retain 50% of the original amino acid residues. The program utilizes a genetic algorithm to optimize the sequence, together with empirical potentials of mean force to evaluate the sequence-structure compatibility. Although the designed sequence has little ordered (secondary) structure in water, circular dichroism and nuclear magnetic resonance data show clear evidence for significant helical content in water/ethylene glycol and in water/methanol mixtures at low temperatures, as well as melting behavior indicative of cooperative folding. We believe that this represents a significant step toward meeting the Paracelsus Challenge.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Successful protein fold recognition by optimal sequence threading validated by rigorous blind testing (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 387-397 
    Details
    ISSN: 0887-3585
    Keywords: protein structure prediction ; threading ; protein sequence analysis ; protein folding ; computational methods ; dynamic programming algorithms ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Analysis of the results of the recent protein structure prediction experiment for our method shows that we achieved a high level of success, Of the 18 available prediction targets of known structure, the assessors have identified 11 chains which either entirely match a previously known fold, or which partially match a substantial region of a known fold. Of these 11 chains, we made predictions for 9, and correctly assigned the folds in 5 cases. We have also identified a further 2 chains which also partially match known folds, and both of these were correctly predicted. The success rate for our method under blind testing is therefore 7 out of 11 chains. A further 2 folds could have easily been recognized but failed due to either overzealous filtering of potential matches, or to simple human error on our part. One of the two targets for which we did not submit a prediction, prosubtilisin, would not have been recognized by our usual criteria, but even in this case, it is possible that a correct prediction could have been made by considerin a combination of pairwise energy and solvation energy Z-scores. Inspection of the threading alignments for the (αβ)8 barrels provides clues as to how fold recognition by threading works, in that these folds are recognized by parts rather than as a whole. The prospects for developing sequence threading technology further is discussed. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340230312
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  • 10
    Electronic Resource
    Electronic Resource
    Successful ab initio prediction of the tertiary structure of NK-lysin using multiple sequences and recognized supersecondary structural motifs (1997)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 29 (1997), S. 185-191 
    Details
    ISSN: 0887-3585
    Keywords: protein structure prediction ; potentials of mean force ; ab initio folding ; structural motifs ; simulated annealing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A simple approach to protein tertiary structure prediction is described, based on the assembly of recognized supersecondary structural fragments taken from highly resolved protein structures by using a simulated annealing algorithm. The results of blind-testing this method on CASP2 target T0042 (pig NK-lysin) are presented. The predicted structure had a Cα root-mean-square deviation of only 6.2 Å from the experimental structure (and less than 5.0 Å over the first 66 residues), and clearly had the correct fold when judged by using a number of objective measures. Despite the significant degree of success in this case, there is clearly much more development required before predictions with the accuracy of a good homology model can be made with this kind of approach. Proteins, Suppl. 1:185-191, 1997. © 1998 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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