Improving fragmentation of poorly fragmenting peptides and phosphopeptides during collision-induced dissociation by malondialdehyde modification of arginine residues
作者:Alexander Leitner、Alexandra Foettinger、Wolfgang Lindner
DOI:10.1002/jms.1233
日期:2007.7
Despite significant technological and methodological advancements in peptide sequencing by mass spectrometry, analyzing peptides that exhibit only poor fragmentation upon collision-induced dissociation (CID) remains a challenge. A major cause for unfavorable fragmentation is insufficient proton ‘mobility’ due to charge localization at strongly basic sites, in particular, the guanidine group of arginine. We have recently demonstrated that the conversion of the guanidine group of the arginine side chain by malondialdehyde (MDA) is a convenient tool to reduce the basicity of arginine residues and can have beneficial effects for peptide fragmentation. In the present work, we have focused on peptides that typically yield incomplete sequence information in CID-MS/MS experiments. Energy-resolved tandem MS experiments were carried out on angiotensins and arginine-containing phosphopeptides to study in detail the influence of the modification step on the fragmentation process. MDA modification dramatically improved the fragmentation behavior of peptides that exhibited only one or two dominant cleavages in their unmodified form. Neutral loss of phosphoric acid from phosphopeptides carrying phosphoserine and threonine residues was significantly reduced in favor of a higher abundance of fragment ions. Complementary experiments were carried out on three different instrumental platforms (triple-quadrupole, 3D ion trap, quadrupole–linear ion trap hybrid) to ascertain that the observation is a general effect. Copyright © 2007 John Wiley & Sons, Ltd.
尽管质谱技术在肽测序方面取得了重大的技术和方法进步,但分析碰撞诱导解离(CID)后碎片不佳的肽仍然是一项挑战。造成碎片不佳的一个主要原因是质子在强碱性位点(尤其是精氨酸的胍基)的电荷定位导致质子 "流动性 "不足。我们最近证明,用丙二醛(MDA)转换精氨酸侧链的胍基是降低精氨酸残基碱性的一种便捷工具,对肽的破碎有好处。在本研究中,我们重点研究了在 CID-MS/MS 实验中通常会产生不完整序列信息的肽段。我们对血管紧张素和含精氨酸的磷酸肽进行了能量分辨串联质谱实验,以详细研究修饰步骤对碎裂过程的影响。MDA 修饰极大地改善了肽的碎裂行为,这些肽在未修饰状态下只有一到两种主要裂解。携带磷酸丝氨酸和苏氨酸残基的磷酸肽的磷酸中性损失显著减少,碎片离子的丰度更高。在三种不同的仪器平台(三重四极杆、三维离子阱、四极杆线性离子阱混合型)上进行了补充实验,以确定该观察结果是一种普遍效应。Copyright © 2007 John Wiley & Sons, Ltd. All Rights Reserved.