Bio-Nanotechnology Center, Department of Chemistry, Pohang University of Science and Technology, Pohang, Korea.
Mass Spectrom Rev. 2015 Mar-Apr;34(2):209-18. doi: 10.1002/mas.21435. Epub 2014 May 28.
Isobaric tags have been widely used for the identification and quantification of proteins in mass spectrometry-based proteomics. The mass-balanced, (1) H/(2) H isotope-coded dipeptide tag (MBIT) is a multifunctional isobaric tag based on N-acetyl-Ala-Ala dipeptide containing an amine-reactive linker that conjugates the tag to the primary amines of proteolytic peptides. MBITs provide a pair of isotope-coded quantitation signals separated by 3 Da, which enables 2-plex quantification and identification of proteins in the 15-250 fmol range. Various MBITs diversified at the N-acetyl group or at the side chain of the first alanine provide a pair of bs ions as low-mass quantitation signals in a distinct mass window. Thus, a combination of different MBITs allows multiplex quantification of proteins in a single liquid chromatography-mass spectrometry experiment. Unlike other isobaric tags, MBITs also offer a pair of ys ions as high-mass quantitation signals in a noise-free region, facilitating protein quantification in quadrupole ion trap mass spectrometers. Uniquely, bS ions, forming N-protonated oxazolone, undergo unimolecular dissociation and generate the secondary low-mass quantitation signals, aS ions. The yield of aS ions derived from bS ions can be used to measure the temperature of bS ions, which enables a reproducible acquisition of the peptide tandem mass spectra. Thus, MBITs enable multiplexed quantitation of proteins and the concurrent measurement of ion temperature using bS and aS signal ions as well as the isobaric protein quantitation in resonance-type ion trap using yS (complement of bS ) signal ions. This review provides an overview of MBITs with a focus on the multi-functionality that has been successfully demonstrated in the peptide tandem mass spectrometry.
同位素质谱标签已被广泛用于基于质谱的蛋白质组学中蛋白质的鉴定和定量。质量平衡、（1）H/（2）H 同位素编码二肽标签（MBIT）是一种基于 N-乙酰-Ala-Ala 二肽的多功能同位素质谱标签，其中含有一个胺反应性接头，可将标签与肽的伯胺连接。MBIT 提供一对分离 3Da 的同位素编码定量信号，能够在 15-250 fmol 范围内进行 2 重定量和蛋白质鉴定。各种在 N-乙酰基或第一个丙氨酸的侧链上多样化的 MBIT 提供一对 bs 离子作为低质量定量信号，在一个独特的质量窗口中。因此，不同的 MBIT 组合允许在单个液相色谱-质谱实验中对蛋白质进行多重定量。与其他同位素质谱标签不同，MBIT 还提供一对 ys 离子作为高质量定量信号，在无噪声区域中，便于在四极离子阱质谱仪中进行蛋白质定量。独特的是，bs 离子形成 N-质子化恶唑酮，经历单分子解离并产生二次低质量定量信号 aS 离子。从 bs 离子衍生的 aS 离子的产率可用于测量 bs 离子的温度，从而能够重复获取肽串联质谱。因此，MBIT 能够对蛋白质进行多重定量，并同时测量离子温度，使用 bs 和 aS 信号离子，以及使用 ys（bs 的互补物）信号离子在共振型离子阱中进行同位素质谱标签蛋白质定量。本文综述了 MBIT 的概述，重点介绍了在肽串联质谱中成功证明的多功能性。
