The effect of adding ethylammonium nitrate (EAN), which is an ionic liquid (IL), on the aggregate formation of α-synuclein (α-Syn) in aqueous solution has been investigated. FTIR and Raman spectroscopy were used to investigate changes in the secondary structure of α-Syn and in the states of water molecules and EAN. The results presented here show that the addition of EAN to α-Syn causes the formation of an intermolecular β-sheet structure in the following manner: native disordered state → polyproline II (PPII)-helix → intermolecular β-sheet (α-Syn amyloid-like aggregates: α-SynA). Although cations and anions of EAN play roles in masking the charged side chains and PPII-helix-forming ability involved in the formation of α-SynA, water molecules are not directly related to its formation. We conclude that EAN-induced α-Syn amyloid-like aggregates form at hydrophobic associations in the middle of the molecules after masking the charged side chains at the N- and C-terminals of α-Syn.

中文翻译：

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α-突触核蛋白聚集体在乙基硝酸铵水溶液中的形成

已经研究了添加作为离子液体 (IL) 的乙基硝酸铵 (EAN) 对水溶液中 α-突触核蛋白 (α-Syn) 聚集体形成的影响。FTIR 和拉曼光谱用于研究 α-Syn 二级结构的变化以及水分子和 EAN 状态的变化。此处显示的结果表明，将 EAN 添加到 α-Syn 会以下列方式导致分子间 β-折叠结构的形成：天然无序状态 → 聚脯氨酸 II (PPII)-螺旋 → 分子间β-折叠（α-Syn 淀粉样蛋白） -样聚集体：α-SynA）。尽管 EAN 的阳离子和阴离子在掩蔽带电侧链和参与 α-SynA 形成的 PPII 螺旋形成能力方面发挥作用，但水分子与其形成没有直接关系。