3‐Mercaptopropionic acid modified ZnSe quantum dots as the matrix for direct surface‐assisted laser desorption/ionization mass spectrometric analysis of peptides/proteins from sodium salt solution

Abstract

This study describes a strategy of using zinc selenium quantum dots (ZnSe QDs) modified with 3-mercaptopropionic acid (3-MPA) as the matrix for direct analysis of peptides and proteins from sodium salt solution in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). The enhancement of detection sensitivity for these biomolecules was due to the adsorption of positively charged peptides or proteins onto the surfaces of negatively charged ZnSe-3MPA QDs via electrostatic interactions resulting in an increase in ionization efficiency for sodium adduct ions ([M+Na] + ). The applicability of the current approach was demonstrated for a variety of peptides, including leucine-enkephalin, methione-enkephalin, HW6, substance P and angiotensin II, and proteins (cytochrome c, myoglobin and lysozyme). Signal intensities of these peptides or proteins can be enhanced by 25-95 times compared with those obtained by LDI-MS in the absence of ZnSe-3MPA QDs. Applying ZnSe-3MPA QDs to serve as the matrix in SALDI-MS is a simple and effective approach for direct analysis of peptide and protein molecules from sodium salt solution without any pretreatment as the peptides and proteins can be successfully detected as sodium adduct ions ([M+Na] + ).

Nanoparticles for Mass Spectrometry Applications

“…The use of quantum dots (QDs) for SALDI applications has thus far not been widely explored. Among the few existing reports, one describes the use of 3-mercaptopropionic acid (3-MPA)-modified zinc selenide QDs (ZnSe) for SALDI-MS analysis of peptides and proteins from a sodium salt solution [68]. The analytes adsorb to the surface of 3-MPA-modified QDs, resulting in improved ionization, and most peptides and proteins are detected as sodium adduct ions with mass signal intensities enhanced 25-to 95-fold.…”

Nanomaterial-based miniaturized extraction and preconcentration techniques coupled to matrix-assisted laser desorption/ionization mass spectrometry for assaying biomolecules

“…To support this, our group utilized a wide variety of functionalized semiconductor NPs, including ZnS [83,84], Mn 2+ -doped ZnS [85], CdS [86,87], CdSe [88], Cd 2+ -doped CNTs, CdS [89], and ZnSe [90,91], as affinity and concentrating probes for the analysis of peptides and proteins by MALDI-MS. The unique physico-chemical properties of NPs can be controlled and effective trapping or affinity agents made by modifying the surfaces of NPs with suitable organic ligands.…”

“…Similarly, MPA-capped ZnSe-QDs were used as matrix and affinity probes for direct analysis of peptides and proteins in SALDI-MS [90]. The signal enhancement was due to the adsorption of positively-charged peptides or proteins onto the surfaces of negativelycharged ZnSe-QDs via electrostatic interactions, so enhancing the ionization efficiency of target analytes with improved signal intensities.…”

Semiconductor Nanomaterials-Based Fluorescence Spectroscopic and Matrix-Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometric Approaches to Proteome Analysis

“…Therefore, Wu’s group introduced various functionalized semiconductor nanomaterials and used as matrices, affinity probes and heat absorbing probes for the analysis of peptides, proteins and bacteria by LDI- and MALDI-MS [96,97,98,99,100,101,102,103,104,105]. Briefly, the ZnS NPs were functionalized with five different functional groups (MPA, sodium citrate, cysteamine, and 2-mercaptoethane sulfonate) and used as affinity probes for the analysis of proteins by MALDI-MS [96].…”

“…Furthermore, MPA capped ZnSe QDs were used as the matrix and affinity probes for direct analysis of peptides and proteins from sodium salt solution in SALDI-MS [104,105]. The signal enhancement was owing to the electrostatic interaction between QDs and biomolecules, which facilitate the adsorbtion proteins onto the surfaces of ZnSe QDs.…”