TY - JOUR
T1 - Iodine staining as a useful probe for distinguishing insulin amyloid polymorphs
AU - Hiramatsu, Takato
AU - Yamamoto, Naoki
AU - Ha, Seongmin
AU - Masuda, Yuki
AU - Yasuda, Mitsuru
AU - Ishigaki, Mika
AU - Yuzu, Keisuke
AU - Ozaki, Yukihiro
AU - Chatani, Eri
N1 - Funding Information:
We thank Tomomi Kozu (Renishaw K.K.) for help of resonance Raman measurements and Prof. Masahide Yamamoto (Kyoto University) for valuable comments on iodine-polymer complexes. AFM measurements were performed at Research Facility Center for Science and Technology, Kobe University. This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks. This work was funded by JSPS KAKENHI Grant Numbers JP16H04778, JP16H00772, JP17H06352, and JP20K21396.
Publisher Copyright:
© 2020, The Author(s).
PY - 2020/12/1
Y1 - 2020/12/1
N2 - It is recently suggested that amyloid polymorphism, i.e., structural diversity of amyloid fibrils, has a deep relationship with pathology. However, its prompt recognition is almost halted due to insufficiency of analytical methods for detecting polymorphism of amyloid fibrils sensitively and quickly. Here, we propose that iodine staining, a historically known reaction that was firstly found by Virchow, can be used as a method for distinguishing amyloid polymorphs. When insulin fibrils were prepared and iodine-stained, they exhibited different colors depending on polymorphs. Each of the colors was inherited to daughter fibrils by seeding reactions. The colors were fundamentally represented as a sum of three absorption bands in visible region between 400 and 750 nm, and the bands showed different titration curves against iodine, suggesting that there are three specific iodine binding sites. The analysis of resonance Raman spectra and polarization microscope suggested that several polyiodide ions composed of I3− and/or I5− were formed on the grooves or the edges of β-sheets. It was concluded that the polyiodide species and conformations formed are sensitive to surface structure of amyloid fibrils, and the resultant differences in color will be useful for detecting polymorphism in a wide range of diagnostic samples.
AB - It is recently suggested that amyloid polymorphism, i.e., structural diversity of amyloid fibrils, has a deep relationship with pathology. However, its prompt recognition is almost halted due to insufficiency of analytical methods for detecting polymorphism of amyloid fibrils sensitively and quickly. Here, we propose that iodine staining, a historically known reaction that was firstly found by Virchow, can be used as a method for distinguishing amyloid polymorphs. When insulin fibrils were prepared and iodine-stained, they exhibited different colors depending on polymorphs. Each of the colors was inherited to daughter fibrils by seeding reactions. The colors were fundamentally represented as a sum of three absorption bands in visible region between 400 and 750 nm, and the bands showed different titration curves against iodine, suggesting that there are three specific iodine binding sites. The analysis of resonance Raman spectra and polarization microscope suggested that several polyiodide ions composed of I3− and/or I5− were formed on the grooves or the edges of β-sheets. It was concluded that the polyiodide species and conformations formed are sensitive to surface structure of amyloid fibrils, and the resultant differences in color will be useful for detecting polymorphism in a wide range of diagnostic samples.
UR - http://www.scopus.com/inward/record.url?scp=85092146713&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85092146713&partnerID=8YFLogxK
U2 - 10.1038/s41598-020-73460-y
DO - 10.1038/s41598-020-73460-y
M3 - Article
C2 - 33028868
AN - SCOPUS:85092146713
VL - 10
JO - Scientific Reports
JF - Scientific Reports
SN - 2045-2322
IS - 1
M1 - 16741
ER -