- Solution structure of amyloid β-peptide (25-35) in different media
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The design of molecules able to interact with the amyloid peptides either as inhibitors of fibril formation or as inhibitors of amyloid membrane pore formation represents one of the most relevant approaches in the development of anti-Alzheimer therapies. Aβ-(25-35), sequence GSNKGAIIGLM, is a highly toxic synthetic derivative of amyloid β-peptides (Aβ-peptides), which forms fibrillary aggregates. Here, we report the NMR and CD investigation of Aβ-(25-35) in a membrane-mimicking environment and in isotropic mixtures of water and fluoroalcohols to scan its conformational properties as a function of the medium. The analysis of the 3D structures in the mentioned conditions indicates a propensity of the peptide to behave as a typical transmembrane helix in the lipidic environment. In media characterized by different polarity, it loses the structural regularity at specific points of the sequence as a function of the environment. Furthermore, a comparison with the solution structure of full-length amyloid peptides suggests a role for the 25-27 kink region, which appears to be a general feature of all peptides under the solution conditions explored.
- D'Ursi, Anna M.,Armenante, Maria R.,Guerrini, Remo,Salvadori, Severo,Sorrentino, Giuseppe,Picone, Delia
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- Piperazine and DBU: A safer alternative for rapid and efficient Fmoc deprotection in solid phase peptide synthesis
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In Solid Phase Peptide Synthesis (SPPS), contamination with deletion sequences which often co-elute with the target peptide continues to be a major challenge as these impurities can significantly affect the target peptide's properties. Here, we report an efficient Fmoc-deprotection solution containing piperazine and DBU which can cause complete removal of the Fmoc group in less than a minute. This combination rivals piperidine in speediness as revealed by kinetic studies. We demonstrate the efficiency of the piperazine/DBU solution by synthesizing the polyAla stretch with a significant reduction of deletion products occurring due to partial Fmoc deprotection. We verify the utility of the deprotection solution by successfully synthesizing four aggregation prone difficult peptide sequences. We further demonstrate that this combination can also be used to synthesize aspartimide and epimerization prone sequences when supplemented with 1% formic acid and is compatible with 2-chlorotrityl chloride resin. We conclude that piperazine/DBU can be used as a safer and effective alternative to piperidine in Fmoc-SPPS.
- Ralhan, Krittika,KrishnaKumar, V. Guru,Gupta, Sharad
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p. 104417 - 104425
(2015/12/24)
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- Synthesis of chemically-tethered amyloid-β segment trimer possessing amyloidogenic properties
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As amyloid-β (Aβ) undergoes dynamic aggregation, it is impossible to isolate ('hook') the transient Aβ oligomer in an assembly state-pure form (e.g., sole Aβ dimer, trimer, tetramer, etc.). Obtaining such a pure Aβ oligomer would allow us to establish an in vitro system to perform a more detailed investigation of the pathogenic properties of the oligomer. A chemically-tethered Aβ oligomer, constructed only by covalent bonds, could satisfy this demand. Here we designed a chemically-tethered trimer of a pathogenic Aβ fragment (Aβ25-35) (1) and successfully generated it in situ from its precursor (4), a water-soluble and non-aggregative O-acyl isopeptide of 1, in neutral aqueous media. Chemically-tethered 1 possessed stronger amyloidogenic properties, that is, potential for β-sheet structure, fibril formation, and cytotoxicity, than the corresponding monomer Aβ25-35 (6). Trimerization of Aβ25-35 sequence might affect both the aggregative properties and cytotoxicity, based on the present results. This work opens the door for chemical synthesis of oligomers bigger than trimers in an assembly state-pure form, allowing for identification of the most toxic Aβ oligomer.
- Shinoda, Kiyomichi,Sohma, Youhei,Kanai, Motomu
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supporting information
p. 2976 - 2979
(2015/06/22)
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