Characterization of 6‐bromoferulic acid as a novel common‐use matrix for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Abstract

Rationale Ferulic acid (FA) is a standard matrix used for analyzing proteins. In this study, the ability of a halogenated FA to serve as an effective MALDI matrix was investigated. Various halogenated FAs were synthesized, and the characteristics and performance of each were compared with those of the standard matrices α‐cyano‐4‐hydroxycinnamic acid (CHCA) and 2,5‐dihydrobenzoic acid (DHBA). Methods The abilities of 6‐bromoferulic acid (6‐BFA), ferulic acid (FA), and eight other halogenated FA derivatives to ionize eight synthetic peptides were examined. Absorption measurements, MM2 structure optimizations, and proton affinity (PA) calculations were also performed for 6‐BFA and FA. The suitabilities of these compounds as matrices for matrix‐assisted laser desorption/ionization (MALDI) for lipids, sugar chains, polymers, cyanocobalamin, synthetic peptides, and tryptic peptides originating from two types of serum proteins were also tested. Results The 6‐position of FA was found to be the best site for introducing a bromine because the generated compound allowed facile detection of cyanocobalamin and several peptides. 6‐BFA exhibited good sensitivity for large peptides (3–5 kDa) and peptides containing acidic amino acids or proline. 6‐BFA was also shown to be a suitable matrix for tandem mass spectrometry (MS/MS) analysis when using MALDI time‐of‐flight (TOF) mass spectrometry (MS) with a quadrupole ion trap (QIT) system. Conclusions The properties of 6‐BFA as a MALDI matrix differed from those of DHBA and CHCA. 6‐BFA appears to be a useful matrix for de novo sequencing using MALDI‐QIT‐TOF‐MS.

Analysis of carbohydrates and glycoconjugates by matrix‐assisted laser desorption/ionization mass spectrometry: An update for 2019–2020

“…[M + alkali metal] + ions were formed with carbohydrates and, using fructose, the authors found that the peak intensity decreased with increasing atomic weight of the adduct (Li–Cs). Following the observation that introduction of chlorine into the 4‐position of CHCA improved its performance, Kato et al (2020) have investigated the effect of adding halogens to the matrix ferulic acid, sometimes used for proteins. 6‐Bromoferulic acid ( 14 ), although exhibiting improved sensitivity for acidic proteins, was found not to produce signals from carbohydrates either in positive or negative ion modes.…”