Temperature-dependent beta-sheet formation in beta-amyloid Abeta(1-40) peptide in water: uncoupling beta-structure folding from aggregation.
To probe the role of temperature in the conversion of soluble Alzheimer's beta-amyloid peptide (Abeta) to insoluble beta-sheet rich aggregates, we analyzed the solution conformation of Abeta(1-40) from 0 to 98 degrees C by far-UV circular dichroism (CD) and native gel electrophoresis. The CD spectra of 15-300 microg/ml Abeta(1-40) in aqueous solution (pH approximately 4.6) at 0 degrees C are concentration-independent and suggest a substantially unfolded and/or unusually folded conformation characteristic of Abeta monomer or dimer. Heating from 0 to 37 degrees C induces a rapid reversible coil to beta-strand transition that is independent of the peptide concentration and thus is not linked to oligomerization. Consequently, this transition may occur within the Abeta(1-40) monomer or dimer. Incubation at 37 degrees C leads to slow reversible concentration-dependent beta-sheet accumulation; heating to 85 degrees C induces further beta-sheet folding and oligomerization. Our results demonstrate the importance of temperature and thermal history for the conformation of Abeta.
Gursky
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Department of Biophysics, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118-2526, USA. gursky@med-biophd.bu.edu
Aleshkov
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S
D016229:Amyloid beta-Peptides / Q000737:chemistry*; D002021:Buffers; D002942:Circular Dichroism; D004586:Electrophoresis; D010446:Peptide Fragments / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012995:Solubility; D013696:Temperature; D014867:Water
D016229:Amyloid beta-Peptides; D002021:Buffers; D010446:Peptide Fragments; D014867:Water