Ultrafast analysis of peptides by laser diode thermal desorption–triple quadrupole mass spectrometry

Abstract

Rationale:The COVID-19 pandemic demonstrated the importance of highthroughput analysis for public health. Given the importance of surface viral proteins for interactions with healthy tissue, they are targets of interest for mass spectrometry-based analysis. For that reason, the possibility of detecting and quantifying peptides using a high-throughput technique, laser diode thermal desorption-triple quadrupole mass spectrometry (LDTD-QqQMS), was explored.Methods: Two peptides used as models for small peptides (leu-enkephalin and endomorphin-2) and four tryptic peptides (GVYYPDK, NIDGYFK, IADYNYK, and QIAPGQTGK) specific to the SARS-CoV-2 Spike protein were employed. Target peptides were analyzed individually in the positive mode by LDTD-QqQMS. Peptides were quantified by internal calibration using selected reaction monitoring transitions in pure solvents and in samples spiked with 20 μg mL À1 of a bovine serum albumin tryptic digest to represent real analysis conditions.Results: Low-energy fragment ions (b and y ions) as well as high-energy fragment ions (c and x ions) and some of their corresponding water or ammonia losses were detected in the full mass spectra. Only for the smallest peptides, leu-enkephalin and endomorphin-2, were [M + H] + ions observed. Product ion spectra confirmed that, with the experimental conditions used in the present study, LDTD transfers a considerable amount of energy to the target peptides. Quantitative analysis showed that it was possible to quantify peptides using LDTD-QqQMS with acceptable calibration curve linearity (R 2 > 0.99), precision (RSD < 18.2%), and trueness (bias < 8.3%).Conclusions: This study demonstrated for the first time that linear peptides can be qualitatively and quantitatively analyzed using LDTD-QqQMS. Limits of quantification and dynamic ranges are still inadequate for clinical applications, but other applications where higher levels of proteins must be detected could be possible with LDTD. Given the high-throughput capabilities of LDTD-QqQMS (>15 000 samples in less than 43 h), more studies are needed to improve the sensitivity for peptide analysis of this technique.

A comprehensive profiling of renin–angiotensin system in mouse and human plasma by a rapid quantitative analysis of 14 angiotensin peptides using ultrahigh‐performance liquid chromatography with tandem mass spectrometry

“…Mass spectrometry coupled with ultrahigh-performance liquid chromatography (UHPLC/MS) is an effective biological analysis tool, which is widely used in the identification and quantification of proteins and peptides. [29][30][31][32][33][34] Ang peptides are usually double-charged ions at physiological pH (similar to 7.4), which distinguishes their isotope pattern from those of most single-charged small molecules and chemical noise, thereby improving the sensitivity and detection limit. 25 In addition, the combination of high sensitivity and highthroughput sample processing and analytical steps make this method an ideal choice for this type of analysis.…”