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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    International journal of peptide research and therapeutics 2 (1996), S. 285-288 
    ISSN: 1573-3904
    Keywords: Amino acid fluorides ; Coupling reagents ; Fluorination ; Solid phase synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary DAST [(diethylamino)sulfur trifluoride] has shown to be an excellent alternative fluorinating agent for synthesis of Fmoc-amino acid fluorides. The use of DAST is advantageous relative to other fluorinating agents, such as cyanuric fluoride, since handling and isolation of the acid fluorides are facile.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The HPLC retention behavior of three complete single methionine and methionine sulfoxide replacement sets of two 18-mer model peptides and neuropeptide Y (NPY) were investigated. All peptides were prepared by multiple solid-phase peptide synthesis. Plotting the retention time differences between methionine and methionine sulfoxide analogues vs the position of replacement shows that potentially α-helical peptides become helical on binding during reversed-phase high performance liquid chromatography. In the case of an amphipathic α-helix, the retention time differences change periodically with a 3-4 repeat pattern, which allow the location of amphipathic helical structures. Replacements in nonamphipathic α-helical domains cause local preferential binding areas and lead to sequence-dependent retention time profiles. Methionine replacement studies of NPY suggest an unstructured or extended conformation from Tyr1 to Ala12 connected to a well-defined amphipathic α-helix from Pro13 to Arg35. The assignment is confirmed by comparison of nuclear Overhauser effects based two-dimensional 1H-nmr spectroscopy and utilization of the CαH shift index method in 50% trifluoroethanol/50% water. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Publication Date: 2022-05-26
    Description: © The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Journal of Cell Biology 198 (2012): 1075-1091, doi:10.1083/jcb.201204024.
    Description: Sperm, navigating in a chemical gradient, are exposed to a periodic stream of chemoattractant molecules. The periodic stimulation entrains Ca2+ oscillations that control looping steering responses. It is not known how sperm sample chemoattractant molecules during periodic stimulation and adjust their sensitivity. We report that sea urchin sperm sampled molecules for 0.2–0.6 s before a Ca2+ response was produced. Additional molecules delivered during a Ca2+ response reset the cell by causing a pronounced Ca2+ drop that terminated the response; this reset was followed by a new Ca2+ rise. After stimulation, sperm adapted their sensitivity following the Weber–Fechner law. Taking into account the single-molecule sensitivity, we estimate that sperm can register a minimal gradient of 0.8 fM/µm and be attracted from as far away as 4.7 mm. Many microorganisms sense stimulus gradients along periodic paths to translate a spatial distribution of the stimulus into a temporal pattern of the cell response. Orchestration of temporal sampling, resetting, and adaptation might control gradient sensing in such organisms as well.
    Description: This work was supported by the German Research Foundation and the Fonds der Chemischen Industrie.
    Description: 2013-03-17
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: video/quicktime
    Format: application/pdf
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