Abstract:
:We aimed to investigate insulin amyloid fibril polymorphism caused by salt effects and heating temperature and to visualize the structural differences of the polymorphisms in situ using Raman imaging without labeling. The time course monitoring for amyloid formation was carried out in an acidic condition without any salts and with two species of salts (NaCl and Na2SO4) by heating at 60, 70, 80, and 90°C. The intensity ratio of two Raman bands at 1672 and 1657 cm-1 due to antiparallel β-sheet and α-helix structures, respectively, was revealed to be an indicator of amyloid fibril formation, and the relative proportion of the β-sheet structure was higher in the case with salts, especially at a higher temperature with Na2SO4. In conjunction with the secondary structural changes of proteins, the S-S stretching vibrational mode of a disulfide bond (∼514 cm-1) and the ratio of the tyrosine doublet I850/I826 were also found to be markers distinguishing polymorphisms of insulin amyloid fibrils by principal component analysis. Especially, amyloid fibrils with Na2SO4 media formed the gauche-gauche-gauche conformation of disulfide bond at a higher rate, but without any salts, the gauche-gauche-gauche conformation was partially transformed into the gauche-gauche-trans conformation at higher temperatures. The different environments of the hydroxyl groups of the tyrosine residue were assumed to be caused by fibril polymorphism. Raman imaging using these marker bands also successfully visualized the two- and three- dimensional structural differences of amyloid polymorphisms. These results demonstrate the potential of Raman imaging as a diagnostic tool for polymorphisms in tissues of amyloid-related diseases.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Ishigaki M,Morimoto K,Chatani E,Ozaki Ydoi
10.1016/j.bpj.2020.04.031subject
Has Abstractpub_date
2020-06-16 00:00:00pages
2997-3007issue
12eissn
0006-3495issn
1542-0086pii
S0006-3495(20)30375-1journal_volume
118pub_type
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