title: Alkylated dihydroxybenzoic acid as a MALDI matrix additive for hydrophobic peptide analysis.
abstract: Hydrophobic peptides are generally difficult to detect using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) because the majority of MALDI matrixes are hydrophilic and therefore have a low affinity for hydrophobic peptides. Here, we report on a novel matrix additive, o-alkylated dihydroxybenzoic acid (ADHB), which is a 2,5-dihydroxybenzoic acid (DHB) derivative incorporating a hydrophobic alkyl chain on a hydroxyl group to improve its affinity for hydrophobic peptides, thereby improving MALDI-MS sensitivity. The addition of ADHB to the conventional matrix α-cyano-4-hydroxycinnamic acid (CHCA) improved the sensitivity of hydrophobic peptides 10- to 100-fold. The sequence coverage of phosphorylase b digest was increased using ADHB. MS imaging indicated that hydrophobic peptides were enriched in the rim of a matrix/analyte dried spot when ADHB was used. In conclusion, the addition of ADHB to the standard matrix led to improved sensitivity of hydrophobic peptides by MALDI-MS.
authors.affiliation: Koichi Tanaka Laboratory of Advanced Science and Technology, Shimadzu Corporation, 1, Nishinokyo-Kuwabaracho, Nakagyo-ku, Kyoto 604-8511, Japan. yukof@shimadzu.co.jp
authors.forename: Yuko
authors.initials: Y
authors.lastname: Fukuyama
authors.forename: Ritsuko
authors.initials: R
authors.lastname: Tanimura
authors.forename: Kazuki
authors.initials: K
authors.lastname: Maeda
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.forename: Shin-Ichirou
authors.initials: S
authors.lastname: Kawabata
authors.forename: Shinichi
authors.initials: S
authors.lastname: Iwamoto
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Izumi
authors.forename: Koichi
authors.initials: K
authors.lastname: Tanaka
mesh_terms: D000478:Alkylation; D000818:Animals; D003373:Coumaric Acids / Q000737:chemistry; D005841:Gentisates / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000737:chemistry*; D010763:Phosphorylase b / Q000737:chemistry; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D003373:Coumaric Acids; D005841:Gentisates; D010455:Peptides; C007175:alpha-cyano-4-hydroxycinnamate; D010763:Phosphorylase b; C010925:2,5-dihydroxybenzoic acid