When a denatured protein isoform (i.e., a proteoform) immersed in electrolyte is impelled by an electric field through a sub-nanometer-diameter pore (i.e., a sub-nanopore) spanning a thin membrane, the sequence of amino acid (AA) residues constituting the proteoform can be directly "read" one at a time by measuring fluctuations in the electrolytic current. Corroborating this assertion, an analysis of the pore current with molecular dynamic (MD) simulations reveals that the fluctuations are correlated to the sequence of AA volumes, the water in the pore and acid mobility. After alignment to account for variations in the acid mobility, the simulated pore current is nearly perfectly correlated to the pattern of empirical fluctuations. To prove out the prospects for decoding proteoforms this way, site-specific post-translational modifications (PTMs) and point mutations in amyloid-beta (Aβ_1-42) were analyzed with a sub-nanopore. The results show that single acids can be resolved in proteoforms with a dynamic range limited by the size of phenylalanine and glycine. With this sensitivity and single acid resolution, the sequence of a scrambled variant of Aβ_1-42 was discriminated with a p-value < 10-5.

中文翻译：

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使用亚纳米直径孔以单酸分辨率解码蛋白质形式

当浸入电解质中的变性蛋白质异构体（即蛋白质异构体）被电场推动穿过跨越薄膜的亚纳米直径孔（即亚纳米孔）时，氨基酸（AA）残基的序列通过测量电解电流的波动，可以一次直接“读取”一个构成蛋白质形式的蛋白质。通过分子动力学 (MD) 模拟对孔隙电流的分析证实了这一说法，表明波动与 AA 体积的顺序、孔隙中的水和酸的迁移率相关。在考虑酸迁移率的变化后，模拟的孔隙电流几乎与经验波动的模式完全相关。为了证明以这种方式解码蛋白质形式的前景，使用亚纳米孔分析了β淀粉样蛋白（Aβ _1-42 ）的位点特异性翻译后修饰（PTM）和点突变。结果表明，单一酸可以以蛋白质形式解析，其动态范围受苯丙氨酸和甘氨酸的大小限制。凭借这种灵敏度和单酸分辨率，可以以 p 值 < 10-5 区分Aβ _1-42的乱序变体的序列。