规模化蛋白质鉴定中母离子的准确检测技术研究

蛋白质组学的基础研究之一是蛋白质鉴定.规模化的蛋白质鉴定通常采用"鸟枪法",即选择一些酶切肽段(母离子)碎裂生成二级谱图,通过二级谱图及其母离子质量鉴定肽段,再推断对应的蛋白质.在鉴定过程中,母离子质量是一个关键参数.母离子是否是肽段的单同位素峰决定了正确肽段是否能进入候选,母离子的质量精度决定了候选肽段的数目.本文从判断单同位素峰和系统误差校准这两个角度研究了母离子的准确检测技术.判断单同位素峰的技术在蛋白质上已有研究,包括电荷判断、单同位素峰判断和重叠同位素峰判断.可以借鉴蛋白质水平的技术研究母离子的单同位素峰判断方法.同时母离子的系统误差校准也有较为成熟的方法.这两个角度的研究有助于提高规模化蛋白质的鉴定率.

Accurate Determination of Precursor Ions for Peptides in Large-scale Protein Identification

One basic research for proteomics is protein identification. For large-scale protein identification, shotgun techniques are usually applied, i.e., some digested peptides (precursor ions) are chosen to fragment and produce tandem mass spectra, which can be identified by database search, and then proteins can be inferred from the identified peptides. In the identification, precursor mass is a key parameter. Whether the correct peptide is within the peptide candidates depends on whether the precursor mass is the monoisotopic mass. The number of peptide candidates depends on the accuracy of the precursor mass. This research investigates the accurate determination of precursors in terms of monoisotopic peak determination and systematic error elimination. There are some techniques of monoisotopic peak determination on protein level, including charge state determination, monoisotopic peak determination and overlapping cluster determination. Some of them can be used to the monoisotopic peak determination of precursors. Meanwhile, there are some well-known methods for systematic error elimination. The two kinds of techniques for accurate precursor determination can help increase the large-scale protein identification rate.