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  • 1
    Publication Date: 2015-12-18
    Description: Covalent dynamic chemistry is used to mimic the first steps of the highly cooperative fibril formation of Aβ peptides. For that purpose, Aβ peptide pentapeptide boronic acids 1 and 2 were synthesized by solid-phase peptide synthesis and studied in esterification experiments with polyhydroxylated templates. The bis-hydroxylated dipeptide Hot=Tap serves as a template of adjustable degree of oligomerization which spontaneously forms boronic esters with peptides of type 1 and 2 . Nuclear magnetic resonance can differentiate between regioisomeric boronic esters and identifies preferred sites of esterification on the dimeric template 9 . 2-Formylphenylboronic acid ( 14 ) is used to link the parent pentapeptide Leu-Val-Phe-Phe-Ala to the template 16 to obtain threefold boronic ester 17 . The miniamyloid 17 assembles from seven components by imine and boronic ester bonds between the peptides and the template. The relative orientation and spacing of the peptides mimic the assembly of peptides in Alzheimer β-amyloids. Beilstein J. Org. Chem. 2015, 11, 2646–2653. doi:10.3762/bjoc.11.284
    Keywords: Alzheimerboronic acidminiamyloidsNMR spectroscopypeptides
    Electronic ISSN: 1860-5397
    Topics: Chemistry and Pharmacology
    Published by Beilstein-Institut
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  • 2
    Publication Date: 2015-01-08
    Description: Biosilicification sets the standard for the localized in vitro precipitation of silica at low orthosilicate concentrations in aqueous environment under ambient conditions. Numerous parameters must be controlled for the development of new technologies in designing inventive nanosilica structures, which are able to challenge the biological templates. A long neglected requirement that came into focus in the recent years are the cellular techniques of preventing unintentional lithification of cellular structures since numerous cellular components such as membranes, DNA, and proteins are known to precipitate nanosilica. The diatom metabolism makes use of techniques that restrict silicification to an armor of silica around the cell wall while avoiding the petrifying gaze of Medusa, which turns the whole cell into stone. Step by step, biochemistry unveils the hierarchical interplay of an arsenal of low-molecular weight molecules, proteins, and the cytoskeletal architecture and it becomes clearer why the organisms invest much metabolic effort for an obviously simple chemical reaction like the precipitation of amorphous silica. The discrimination between different soluble components in the silicification process (chemoselective silicification) is not only vitally important for the diatom but poses an interesting challenge for in vitro experiments. Until now, silica precipitation studies were mainly focused on the amount, the morphology, and composition of the precipitate while disregarding a quantitative analysis of the remaining soluble components. Here, we turn the tables and quantify the soluble components by 1H NMR in the progress of precipitation and present experiments which quantify the additivity, and potential cooperativity of long chain polyamines (LCPAs) and cationic peptides in the silicification process.
    Electronic ISSN: 2190-4286
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics , Technology
    Published by Beilstein-Institut
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  • 3
    Publication Date: 2015-12-17
    Description: Covalent dynamic chemistry is used to mimic the first steps of the highly cooperative fibril formation of Aβ peptides. For that purpose, Aβ peptide pentapeptide boronic acids 1 and 2 were synthesized by solid-phase peptide synthesis and studied in esterification experiments with polyhydroxylated templates. The bis-hydroxylated dipeptide Hot=Tap serves as a template of adjustable degree of oligomerization which spontaneously forms boronic esters with peptides of type 1 and 2. Nuclear magnetic resonance can differentiate between regioisomeric boronic esters and identifies preferred sites of esterification on the dimeric template 9. 2-Formylphenylboronic acid (14) is used to link the parent pentapeptide Leu-Val-Phe-Phe-Ala to the template 16 to obtain threefold boronic ester 17. The miniamyloid 17 assembles from seven components by imine and boronic ester bonds between the peptides and the template. The relative orientation and spacing of the peptides mimic the assembly of peptides in Alzheimer β-amyloids.
    Print ISSN: 2195-951X
    Electronic ISSN: 1860-5397
    Topics: Chemistry and Pharmacology
    Published by Beilstein-Institut
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