Controlling Solvent Polarity to Regulate Protein Self-Assembly Morphology and Its Universal Insight for Fibrillation Mechanism
Bao Zhang, Ruisheng Jiang, Kexin Dong, Jing Li, Yan Zhang, Behrouz Ghorani, Bahareh Emadzadeh, Katsuyoshi Nishinari, Nan Yang
Abstract
lg) in the acidic aqueous solution upon heating was investigated using various techniques, mainly thioflavin T fluorescence, atomic force microscopy, nonreducing electrophoresis, mass spectrometry, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy. The results showed that fibrillation occurred with a heating time increase, but high ethanol content slowed down the process. At a low ethanol volume fraction, peptides existed after heating for 2 h, with long and straight fibrils formed after 4-6 h, while at a high ethanol volume fraction, the proteins aggregated with very few peptides appeared at the early stage of heating, and short and curved fibrils formed after heating for 8 h. Ethanol weakened the hydrophobic interactions between proteins in the aqueous solution; therefore the latter could not completely balance the electrostatic repulsion, and thus suppressing the fibrillation process. It is believed that the fibrillation of β-lg in the acidic solution upon heating is mainly dominated by the polypeptide model; however, ethanol inhibited the hydrolysis of proteins, and the self-assembly mechanism changed to the monomer model.