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Int. J. Mol. Sci. 2017, 18(12), 2551; https://doi.org/10.3390/ijms18122551

Insights into Insulin Fibril Assembly at Physiological and Acidic pH and Related Amyloid Intrinsic Fluorescence

1
Department of Biochemistry, Biophysics and General Pathology, Università degli Studi della Campania “Luigi Vanvitelli”, 80138 Naples, Italy
2
Department of Experimental Medicine, Università degli Studi della Campania “Luigi Vanvitelli”, 80138 Naples, Italy
*
Author to whom correspondence should be addressed.
Received: 24 October 2017 / Revised: 10 November 2017 / Accepted: 23 November 2017 / Published: 28 November 2017
(This article belongs to the Collection Protein Folding)
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Abstract

Human insulin is a widely used model protein for the study of amyloid formation as both associated to insulin injection amyloidosis in type II diabetes and highly prone to form amyloid fibrils in vitro. In this study, we aim to gain new structural insights into insulin fibril formation under two different aggregating conditions at neutral and acidic pH, using a combination of fluorescence, circular dichroism, Fourier-transform infrared spectroscopy, and transmission electron miscroscopy. We reveal that fibrils formed at neutral pH are morphologically different from those obtained at lower pH. Moreover, differences in FTIR spectra were also detected. In addition, only insulin fibrils formed at neutral pH showed the characteristic blue-green fluorescence generally associated to amyloid fibrils. So far, the molecular origin of this fluorescence phenomenon has not been clarified and different hypotheses have been proposed. In this respect, our data provide experimental evidence that allow identifying the molecular origin of such intrinsic property. View Full-Text
Keywords: protein misfolding; amyloid aggregation; amyloid intrinsic fluorescence protein misfolding; amyloid aggregation; amyloid intrinsic fluorescence
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Iannuzzi, C.; Borriello, M.; Portaccio, M.; Irace, G.; Sirangelo, I. Insights into Insulin Fibril Assembly at Physiological and Acidic pH and Related Amyloid Intrinsic Fluorescence. Int. J. Mol. Sci. 2017, 18, 2551.

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