Cross sections for 61 palmitoylated peptides and 73 cysteine-unmodified peptides are determined and used together with a previously obtained tryptic peptide library to derive a set of intrinsic size parameters (ISPs) for the palmitoyl (Pal) group (1.26 ± 0.04), carboxyamidomethyl (Am) group (0.92 ± 0.04), and the 20 amino acid residues to assess the influence of Pal- and Am-modification on cysteine and other amino acid residues. These values highlight the influence of the intrinsic hydrophobic and hydrophilic nature of these modifications on the overall cross sections. As a part of this analysis, we find that ISPs derived from a database of a modifier on one amino acid residue (CysPal) can be applied on the same modification group on different amino acid residues (SerPal and TyrPal). Using these ISP values, we are able to calculate peptide cross sections to within ± 2% of experimental values for 83% of Pal-modified peptide ions and 63% of Am-modified peptide ions. We propose that modification groups should be treated as individual contribution factors, instead of treating the combination of the particular group and the amino acid residue they are on as a whole when considering their effects on the peptide ion mobility features.

中文翻译：

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棕榈酰化和羧酰胺甲基化肽的内在大小参数

确定了 61 种棕榈酰化肽和 73 种半胱氨酸未修饰肽的横截面，并与先前获得的胰蛋白酶肽库一起使用，以推导出棕榈酰 (Pal) 组 (1.26 ± 0.04)、羧酰胺甲基 ( Am) 组 (0.92 ± 0.04) 和 20 个氨基酸残基，以评估 Pal 和 Am 修饰对半胱氨酸和其他氨基酸残基的影响。这些值突出了这些修饰的固有疏水性和亲水性对整个横截面的影响。作为该分析的一部分，我们发现来自一个氨基酸残基 (CysPal) 修饰符数据库的 ISP 可以应用于不同氨基酸残基 (SerPal 和 TyrPal) 的相同修饰组。使用这些 ISP 值，对于 83% 的 Pal 修饰的肽离子和 63% 的 Am 修饰的肽离子，我们能够计算出在实验值的 ± 2% 以内的肽横截面。我们建议，在考虑修饰组对肽离子迁移率特征的影响时，应将修饰组视为单独的贡献因素，而不是将特定组与其所在氨基酸残基的组合视为一个整体。