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The Formation of Amyloid-Like Fibrils of α-Chymotrypsin in Different Aqueous Organic Solvents

[ Vol. 19 , Issue. 5 ]

Author(s):

L. Maria Simon, Ilona Laczko, Anett Demcsak, David Toth, Marta Kotorman and Livia Fulop   Pages 544 - 550 ( 7 )

Abstract:


The formation of amyloid-like fibrils of α-chymotrypsin was studied in aqueous ethanol, methanol, tertbutanol, dimethylformamide and acetonitrile. Thioflavin T (ThT), Congo red (CR) and 1-anilino-8-naphthalenesulfonic acid (ANS) binding, turbidity, intrinsic fluorescence and far-UV circular dichroism measurements were employed to characterize the amyloid fibril formation. The greatest extent of fibril formation after incubation for 24 h at pH 7.0 and at 24 oC was in ethanol at 55%, in methanol and dimethylformamide (DMF) at 60-70% and in tert-butanol at 60-80%. The ANS binding and intrinsic fluorescence results showed that the hydrophobic residues are more solvent-exposed in the aggregated form of α-chymotrypsin. The ThT, CR binding and far-UV CD measurements indicated that the formation of the cross-β structure of α-chymotrypsin depends on the polarity of the organic solvent. To determine the role of surface charges in the aggregation, chemically modified forms of α-chymotrypsin were prepared. The citraconylated and succinylated enzymes exhibited a higher and the enzyme forms modified with aliphatic aldehydes a lower propensity for aggregation. These results suggest the important role of surface charges in the aggregation of α-chymotrypsin.

Keywords:

Amyloid-like fibril, chemical modification, chymotrypsin, cross β-structure, organic solvent

Affiliation:

Department of Biochemistry and Molecular Biology, Faculty of Science and Informatics, University of Szeged, H-6726 Szeged, Kozepfasor 52, Hungary.



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