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Salt Modulated Fibrillar Aggregation of the Sweet Protein MNEI in Aqueous Solution

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Abstract

The mechanism of conversion of globular native proteins into amyloid fibrils represents one of the most attractive research topics in biophysics, because of its involvement in the development of severe pathologies and in various biotechnological processes. Aqueous medium properties, such as pH and ionic strength, as well as interactions with other species in solution, play a key role in tuning the fibrillization process. Here, we describe a comparative study of the influence of different ions from the Hofmeister series on the thermal unfolding and aggregation propensity of MNEI, a model protein, selected because of its tendency to form amyloid aggregates at acidic pH, even at temperatures well below its melting temperature. By selecting a temperature at which only negligible amounts of protein are unfolded, we have focused on the effect of ions on fibril formation. ThT fluorescence experiments indicated that all the salts examined increased the rate and the extent of fibrillization. Moreover, we found that anions, particularly sulfate, strongly influence the process, which instead is only marginally affected by different cations. Finally, a specific link to the chloride concentration was detected.

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Acknowledgements

The financial support of the “Fondazione con il Sud” (Grant No. 2011-PDR-19) is gratefully acknowledged. FD was recipient a fellowship financed by Regione Campania (POR Campania FSE 2014–2020).

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  1. Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario di Monte Sant’Angelo, Via Cintia, 80126, Naples, Italy

    Federica Donnarumma, Alessandro Emendato, Serena Leone, Carmine Ercole, Gerardino D’Errico & Delia Picone

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  1. Federica Donnarumma
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  2. Alessandro Emendato
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  3. Serena Leone
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Correspondence to Gerardino D’Errico or Delia Picone.

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Donnarumma, F., Emendato, A., Leone, S. et al. Salt Modulated Fibrillar Aggregation of the Sweet Protein MNEI in Aqueous Solution. J Solution Chem 47, 939–949 (2018). https://doi.org/10.1007/s10953-018-0764-6

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