Analysis of insulin amyloid fibrils by Raman spectroscopy.
The formation of amyloid fibrils from insulin is investigated using drop-coating-deposition-Raman (DCDR) difference spectroscopy and atomic force microscopy (AFM). Fibrils formed using various co-solvents and heating cycles are found to induce the appearance of Raman difference peaks in the amide I (approximately 1675 cm(-1)), amide III (approximately 1220 cm(-1)), and peptide backbone (approximately 1010 cm(-1)), consistent with an increase in beta-sheet content. Comparisons of results obtained from fibrils in either H2O or D2O suggest that the NH/ND stretch bands (at approximately 3300 cm(-1)/ approximately 2400 cm(-1)) are also enhanced in intensity upon fibril formation. If there is any water trapped in the core of the fibrils its OH/OD Raman intensity is too small to be detected in the presence of the stronger NH/ND bands which appear in the same region. AFM is used to confirm the formation of fibrils of about 5 nm diameter (and various lengths).
Ortiz
Corasi
C
Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
Zhang
Dongmao
D
Ribbe
Alexander E
AE
Xie
Yong
Y
Ben-Amotz
Dor
D
D000682:Amyloid / Q000737:chemistry*; D007328:Insulin / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D013059:Spectrum Analysis, Raman
D000682:Amyloid; D007328:Insulin