title: Coumarins as new matrices for matrix-assisted laser-desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of hydrophobic compounds.
abstract: Hydrophobic compounds with hydroxyl, aldehyde or ketone groups are generally difficult to detect using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), because these compounds have low proton affinity and are poorly ionized by MALDI. Herein, coumarins have been used as new matrices for MALDI-MS analysis of a variety of hydrophobic compounds with low ionization efficiency, including steroids, coenzyme Q10, a cyclic lipopeptide and cholesterol oleate. Five coumarins, including coumarin, umbelliferone, esculetin, 7-hydroxycoumarin-3-carboxylic acid (HCA) and 6,7-dihydroxycoumarin-3-carboxylic acid (DCA), were compared with the conventional matrices of 2,5-dihydroxybenzoic acid (DHB) and α-cyano-4-hydroxycinnamic acid (CHCA). Coumarins with hydroxyl or carboxylic acid groups enabled detection. Taking DCA as an example, this matrix proved to be superior to DHB or CHCA in detection sensitivity, stability, spot-to-spot and sample-to-sample reproducibility, and accuracy. DCA increased the stability of the target compounds and decreased the loss of water. The [M+Na](+) peaks were observed for all target compounds by adding NaCl as an additive, and the [M-H2O+H](+) and [M+H](+) peaks decreased. DCA was selected for the identification of sterols in yeast cells, and thirteen sterols were detected by Fourier transform ion cyclotron resonance (FT ICR) mass spectrometry. This work demonstrates the potential of DCA as a new matrix for detection of hydrophobic molecules by MALDI-MS and provides an alternative tool for screening sterols in antifungal research.
authors.affiliation: Instrumental Analysis Center, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, PR China. Electronic address: hangwang@sjtu.edu.cn.
authors.forename: Hang
authors.initials: H
authors.lastname: Wang
authors.affiliation: Instrumental Analysis Center, Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, PR China.
authors.forename: Bona
authors.initials: B
authors.lastname: Dai
authors.affiliation: Key Laboratory of Kidney Disease Pathogenesis and Intervention of Hubei Province, College of Medicine, Hubei Polytechnic University, Huangshi, Hubei 435003, PR China.
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of Anesthesiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine (SJTU-SM), 197, Rui Jin Er Road, Shanghai 200025, PR China.
authors.forename: Han
authors.initials: H
authors.lastname: Lu
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
keywords: Coumarins; Hydrophobic compounds; Mass spectrometry; Matrix-assisted laser desorption/ionization; Yeast sterols