Alkylated Trihydroxyacetophenone as a MALDI Matrix for Hydrophobic Peptides

Abstract

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.

Coumarins as new matrices for matrix-assisted laser-desorption/ionization Fourier transform ion cyclotron resonance mass spectrometric analysis of hydrophobic compounds

“…We have also developed a simple N-alkylpyridinium isotope quaternization (NAPIQ) method for improving the detection sensitivity for steroids and fatty alcohols by MALDI-MS analysis [20][21][22]. Furthermore, conventional MALDI matrices, including 2,5-dihydroxybenzoic acid (DHB) and a-cyano-4-hydroxycinnamic acid (CHCA), have hydrophilic properties and low affinity for hydrophobic compounds [23,24]. Fukuyama et al have developed alkylated trihydroxyacetophenone and alkylated DHB as MALDI matrices for analysis of hydrophobic peptides [23,24].…”

“…Furthermore, conventional MALDI matrices, including 2,5-dihydroxybenzoic acid (DHB) and a-cyano-4-hydroxycinnamic acid (CHCA), have hydrophilic properties and low affinity for hydrophobic compounds [23,24]. Fukuyama et al have developed alkylated trihydroxyacetophenone and alkylated DHB as MALDI matrices for analysis of hydrophobic peptides [23,24]. 6-Aza-2-thiothymine (ATT) and 4-phenyl-a-cyanocinnamic acid have been used for detecting oxidized phospholipids and lipids, respectively [25,26].…”

Analyses of functional polymer-modified nanoparticles for protein sensing by surface-assisted laser desorption/ionization mass spectrometry coupled with HgTe nanomatrices

“…Accordingly, polydispersity is relatively easier to interpret from the MALDI-MS spectra of polymers [8,9]. The use of organic matrices in MALDI-MS can, however, result in an inhomogeneous distribution of analyte crystals, leading to poor reproducibility [10,11]. In addition, polymers subjected to highpower UV-laser irradiation in MALDI-MS can undergo undesirable fragmentation [12][13][14].…”

Membrane-based detection of lead ions in seawater, urine and drinking straws through laser desorption/ionization

“…To improve the desorption and ionization efficiency of analytes, various organic matrices (e.g., 2,5-dihydroxybenzoic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, ␣-cyano-4-hydroxycinnamic acid, 3-hydroxypicolinic acid) can been employed in LDI-MS to allow the analyses of carbohydrates, nucleic acids, peptides, and proteins [21][22][23]. When performing analyses through matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), these matrices are usually mixed to excess to avoid fragmentation of the analytes under laser irradiation [24][25][26].…”

“…Such non-uniform matrix crystallization or matrix-analyte co-crystallization can lead to poor shot-to-shot and sample-to-sample reproducibilities. In addition, MALDI-MS is rarely applied to low-molecular-weight compounds (<800 Da) because strong background signals can arise from the matrix fragments in the low-mass range [21][22][23][24][25][26]. Moreover, the choice of matrix is usually based on an empirical approach; therefore, matrix selection and optimization of the sample preparation procedure are major issues affecting the success of the MALDI-MS technique.…”