Alkylated trihydroxyacetophenone as a MALDI matrix for hydrophobic peptides.
Hydrophobic peptides are difficult to detect in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), because of the hydrophilic properties of conventional matrices and the low affinity for hydrophobic peptides. Recently, we reported on alkylated dihydroxybenzoic acid (ADHB) as a matrix additive for hydrophobic peptides; however, the peptides were detected in the rim of the matrix-analyte dried spot. Here, we report on a novel matrix, alkylated trihydroxyacetophenone (ATHAP), which is a 2,4,6-trihydroxyacetophenone derivative incorporating a hydrophobic alkyl chain on the acetyl group and thus is expected to have an affinity for hydrophobic peptides. ATHAP increased the sensitivity of hydrophobic peptides 10-fold compared with α-cyano-4-hydroxycinnamic acid (CHCA), in which the detection of hydrophilic peptides was suppressed. The peptides were detected throughout the entire matrix-analyte dried spot using ATHAP, overcoming the difficulty of finding a "sweet spot" when using ADHB. In addition, ATHAP functioned alone as a matrix, unlike ADHB as an additive. In phosphorylase b digests analysis, hydrophobic peptides, which were not detected with CHCA for 1 pmol, were detected with this matrix, confirming that ATHAP led to increased sequence coverage and may extend the range of target analytes in MALDI-MS.
Koichi Tanaka Laboratory of Advanced Science and Technology, Shimadzu Corporation , 1, Nishinokyo-Kuwabaracho, Nakagyo-ku, Kyoto 604-8511, Japan.
Yuko
Y
Fukuyama
Chihiro
C
Nakajima
Keiko
K
Furuichi
Kenichi
K
Taniguchi
Shin-Ichirou
S
Kawabata
Shunsuke
S
Izumi
Koichi
K
Tanaka
D000098:Acetophenones / Q000737:chemistry*; D000478:Alkylation; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D010763:Phosphorylase b / Q000378:metabolism; D059748:Proteolysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
D000098:Acetophenones; D010455:Peptides; C107067:2,4,6-trihydroxyacetophenone; D010763:Phosphorylase b