Gao Yuan, Wang Yinsheng
Department of Chemistry-027, University of California at Riverside, Riverside, California 92521-0403, USA.
J Am Soc Mass Spectrom. 2007 Nov;18(11):1973-6. doi: 10.1016/j.jasms.2007.08.010. Epub 2007 Aug 22.
Quantitative assessment of post-translational modifications in proteins by mass spectrometry often requires the consideration of the alteration in ionization efficiency of peptides induced by the modification. Herein, we introduced a method to measure the relative ionization efficiencies of peptides using specifically designed unlabeled peptides. In our design, the peptide under study, in either the unmodified or modified form, is linked with an internal standard peptide via an enzyme cleavage site; thus, after enzymatic digestion, we could obtain readily a 1:1 ratio between the peptide under investigation and the internal standard peptide. The relative ionization efficiencies of the modified and unmodified peptides can then be calculated from the modification-induced change in the ratio of relative abundances of the ion of the peptide of interest over that of the internal standard peptide. We demonstrated the usefulness of the method by assessing the change in ionization efficiencies of four peptides introduced by phosphorylation.
通过质谱对蛋白质翻译后修饰进行定量评估时，通常需要考虑修饰引起的肽段电离效率的变化。在此，我们介绍了一种使用专门设计的未标记肽段来测量肽段相对电离效率的方法。在我们的设计中，所研究的肽段，无论是未修饰形式还是修饰形式，都通过一个酶切位点与内标肽段相连；因此，酶切后，我们可以很容易地得到所研究肽段与内标肽段之间1:1的比例。然后，根据修饰引起的目标肽段离子与内标肽段离子相对丰度比的变化，计算修饰肽段和未修饰肽段的相对电离效率。我们通过评估磷酸化引入的四种肽段的电离效率变化，证明了该方法的实用性。
