A large body of research points to the biological importance of combinatorial post-translational modifications in proteins, such as the active role played by histone modification patterns in the development of cancers, neurodevelopmental disorders, neurodegenerative and other diseases. Nonetheless, our understanding of the precise biological function of different modification patterns is limited by the difficulty of identifying and quantifying different combinatorial isomers in their mixtures as they naturally occur. Tandem mass spectrometry, which infers primary structure from the mass-to-charge ratios of biomolecular fragments, is the preferred method of analysis for proteins and their post-translational modifications. However, the information contained in the mass-to-charge ratios of the individual fragments is frequently insufficient to identify the correct set of modification patterns present in a mixture of combinatorial isomers. This is because no possible single fragment of a combinatorially modified sequence is unique to that sequence in its mass-to-charge ratio. Here we show that the combinatorial post-translational modification problem can be solved by the recently introduced technique of two-dimensional partial covariance mass spectrometry, which provides information about fragment connectivity in a biomolecule by quantifying correlations between the random intensity fluctuations of its fragments, across repeated measurements. Unique fragment-fragment correlations provide the missing link between the non-unique individual fragments to produce unambiguous fingerprints of co-occurring combinatorial isomers, enabling the discovery of biomolecular combinatorial modification patterns by mass spectrometry.

大量的研究指出蛋白质中组合翻译后修饰的生物学重要性，例如组蛋白修饰模式在癌症，神经发育障碍，神经退行性疾病和其他疾病的发展中所起的积极作用。但是，我们对不同修饰形式的精确生物学功能的理解受到鉴定和量化混合物中天然存在的不同组合异构体的困难的限制。从生物分子片段的质荷比推断一级结构的串联质谱法是分析蛋白质及其翻译后修饰的首选方法。然而，单个片段的质荷比中包含的信息通常不足以识别组合异构体混合物中存在的正确的修饰样式集。这是因为在其质荷比方面，组合修饰序列的可能的单个片段都不是该序列唯一的。在这里，我们证明了组合翻译后修饰问题可以通过最近引入的二维部分协方差质谱技术解决，该技术通过量化其片段的随机强度波动之间的相关性来提供有关生物分子中片段连接性的信息。重复测量。