Characterization and Sequence Identification of Angiotensin II by a Novel Method Involving Ultra-Fast Liquid Chromatography Assay Coupled with Matrix-Assisted Laser Desorption/Ionization Quadrupole Ion Trap Time-of-Flight Five Tandem Mass Spectrometry Analysis

High-throughput proteomics aims to investigate dynamically changing proteins expressed by a full organism, specific tissue or cellular compartment under certain conditions. High-sensitivity mass spectrometry has gradually become a significant tool for characterizing peptides. Here, we analyzed angiotensin II using ultra-fast liquid chromatography (UFLC) coupled with matrix-assisted laser desoprtion/ionization time-of-flight mass spectrometry (MALDI-ToF MS). First, we applied UFLC in isolating and collecting the angiotensin II, and then Axima-Resonance (MALDI-QIT-ToF MS⁵) was adopted, which enables collision-induced dissociation–MS⁵ analysis for fine structural characterization of angiotensin II. Resultant MS, MS², MS³ and MS⁴ spectra of interested [M+H]⁺ ions selected as precursor ions yielded detailed information about the sites of fragmentation as well as the amino acid sequence for angiotensin II; meanwhile, the average deviation between theoretical mass and actually measured mass from MS to MS⁵ spectra was only 0.32 Da. It indicated that Axima-Resonance was capable of analysing the peptide sequence accurately and providing the corresponding fragmentation information thoroughly, thus suggesting a potential strategy involving UFLC assay coupled with MALDI-QIT-ToF MS⁵ analysis for high-throughput proteomics studies in the future.