Armirotti Andrea, Millo Enrico, Damonte Gianluca
Department of Experimental Medicine-Biochemistry Section and Center of Excellence for Biomedical Research (DIMES), University of Genoa, Genoa, Italy.
J Am Soc Mass Spectrom. 2007 Jan;18(1):57-63. doi: 10.1016/j.jasms.2006.08.011. Epub 2006 Sep 28.
In peptide sequencing experiments involving a single step tandem mass acquisition, leucine and isoleucine are indistinguishable because both are characterized by a 113 Da mass difference from the other peptide fragments in the MS2 spectrum. In this work, we propose a new method to distinguish between these two amino acids in consecutive MSn experiments, exploiting a gas-phase fragmentation of isoleucine that leads to a diagnostic 69 Da ion. We used this method to assess the Leu/Ile residues of several synthetic peptides. The procedure was then tested on a tryptic digest of myoglobin, assigning the correct amino acid in the majority of the peptides. This work was performed with an old and low-resolution instrument, thus demonstrating that our method is suitable for a wide number of ion trap mass spectrometers, not necessarily expensive or up-to-date.
在涉及单步串联质谱采集的肽测序实验中，亮氨酸和异亮氨酸无法区分，因为在MS2谱图中，它们与其他肽片段的质量差异均为113 Da。在本研究中，我们提出了一种新方法，用于在连续的MSn实验中区分这两种氨基酸，该方法利用异亮氨酸的气相碎裂产生一个具有诊断价值的69 Da离子。我们使用此方法评估了几种合成肽的亮氨酸/异亮氨酸残基。然后在肌红蛋白的胰蛋白酶消化物上测试了该程序，在大多数肽中都正确地确定了氨基酸。这项工作是使用一台老旧且分辨率较低的仪器完成的，这表明我们的方法适用于大量的离子阱质谱仪，不一定需要昂贵或最新的仪器。
