Department of Physical and Analytical Chemistry, University of Oviedo, Oviedo, Spain.
Anal Chem. 2012 Jul 17;84(14):5851-7. doi: 10.1021/ac3009516. Epub 2012 Jun 29.
It is clear that sensitive and interference-free quantification of ICP-detectable elements naturally present in proteins will boost the role of ICPMS in proteomics. In this study, a completely new way of polyatomic interference removal in ICPMS for detection of sulfur (present in the majority of proteins as methionine or cysteine) and phosphorus (present in phosphorylated proteins) is presented. It is based on the concept of tandem mass spectrometry (QQQ) typically used in molecular MS. Briefly, the first quadrupole can be operated as 1 amu window band-pass mass filter to select target analyte ions ((31)P, (32)S, and their on-mass polyatomic interferences). In this way, only selected ions enter the cell and react with O(2), reducing the interferences produced by matrix ions as well as background noise. After optimization of the cell conditions, product ions formed for the targets, (47)PO(+) and (48)SO(+), could be detected with enhanced sensitivity and selectivity. The coupling to capillary HPLC allowed analysis of S- and P-containing species with the lowest detection limits ever published (11 and 6.6 fmol, respectively). The potential of the approach for proteomics studies was demonstrated for the highly sensitive simultaneous absolute quantification of different S-containing peptides and phosphopeptides.
很明显，对蛋白质中天然存在的 ICP 可检测元素进行敏感且无干扰的定量分析，将提高 ICPMS 在蛋白质组学中的作用。在这项研究中，提出了一种完全新颖的方法，可以消除 ICPMS 中多原子干扰，用于检测硫（存在于大多数蛋白质中的蛋氨酸或半胱氨酸）和磷（存在于磷酸化蛋白质中）。它基于串联质谱（QQQ）的概念，通常用于分子 MS。简而言之，第一四极可以作为 1 amu 窗口带通质量滤波器来选择目标分析物离子（(31)P、(32)S 及其同质量多原子干扰）。通过这种方式，只有选定的离子进入细胞并与 O(2)反应，从而减少基质离子产生的干扰和背景噪声。在优化了细胞条件后，可以检测到目标形成的产物离子，(47)PO(+)和(48)SO(+)，从而提高了灵敏度和选择性。与毛细管 HPLC 的耦合允许分析含 S 和 P 的物质，其检测限是有史以来最低的（分别为 11 和 6.6 fmol）。该方法在蛋白质组学研究中的潜力已通过对不同含 S 肽和磷酸肽的高灵敏度同时绝对定量得到证明。
