Nanomaterial-based surface-assisted laser desorption/ionization mass spectrometry of peptides and proteins

Abstract

We have investigated six nanomaterials for their applicability as surfaces for the analyses of peptides and proteins using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Gold nanoparticles (NPs) were useful nanomaterials for small analytes (e.g., glutathione); Pt nanosponges and Fe 3 O 4 NPs were efficient nanomaterials for proteins, with an upper detectable mass limit of ca. 25 kDa. Nanomaterials have several advantages over organic matrices, including lower limits of detection for small analytes and lower batch-to-batch variations (fewer problems associated with "sweet spots"), when used in laser desorption/ionization mass spectrometry. (J Am Soc Mass Spectrom 2010, 21, 1204 -1207) © 2010 American Society for Mass Spectrometry S urface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) was developed recently using nanomaterials rather than organic compounds as matrices, for the determination of analytes of interest. For example, laser desorption/ionization (LDI) of intact proteins and protein aggregates in the presence of glycerol has been demonstrated using cobalt particles (ca. 30 nm) [1]. Similar to the role played by organic matrices, the particles absorb energy from the laser irradiation and transfer it efficiently to the analytes, thereby inducing desorption and ionization. Mixtures of graphite particles (2-150 m) and glycerol have been employed in the analysis of proteins and peptides [2,3]. Several other nanomaterials, including carbon nanotubes, nanodiamonds, and various nanoparticles (NPs, namely SiO 2 , ZnS, TiO 2 , Fe 3 O 4 , Fe 3 O 4 /TiO 2 , and Au) are also useful-without the addition of glycerol-for SALDI-MS [4 -12]. Because of their unique chemical and physical properties, NPs can also act as selective probes and/or efficient ionization nanomaterials. For example, Au and TiO 2 NPs are suitable for the concentration and ionization of aminothiols and catechins, respectively, in SALDI-MS [8,11]. One other advantage of using NPs is that fewer "sweet spots" are formed, thereby maximizing reproducibility. Although NPs have been used successfully for the determination of a range of analytes (from small analytes to proteins), a review of the literature reveals that the various NPs provide quite different results in terms of sensitivity, reproducibility, and mass range. Thus, our aim in this study was to evaluate the performance of several types of NPs for the analysis of peptides and proteins. ExperimentalSix nanomaterials-Au NPs, TiO 2 NPs, Se NPs, CdTe quantum dots (QDs), Fe 3 O 4 NPs, and Pt nanosponges (NSPs)-were tested for the SALDI-MS-based analyses of peptides and proteins; they were prepared in aqueous solutions and characterized according to procedures described in the literature [8,11,[13][14][15][16]. A twolayer preparation method was applied to deposit the nanomaterials and samples onto the metal plates used in SALDI-MS. First, one of the nanomaterial solutions (1 L) was deposited into one of the wells of the MS plate and dried under ambient cond...

Citric Acid Capped Iron Oxide Nanoparticles as an Effective MALDI Matrix for Polymers

“…The lack of matrix molecules/ ions in matrix plume results in clean spectral background in low mass spectral region; however, this fails to carry macromolecules into the gas phase. The upper detected mass limits using various NP matrices are generally below 26 kDa for protein samples and 7 kDa for polymers [34,58]. A HgTe NP matrix was reported to increase the upper mass limit for proteins to 150 kDa [59].…”

“…High molecular mass analysis with NP matrices has been particularly problematic [40,58]. The possible cause is that NPs are heavy and surface bound, and thus do not form an abundant matrix plume like organic matrices.…”

Analysis of Biomolecules through Surface‐Assisted Laser, Desorption/Ionization Mass Spectrometry Employing Nanomaterials

“…Chiang et al studied six different nanomaterials (Au NPs, Fe 3 O 4 NPs, TiO 2 NPs, Se NPs, CdTe quantum dots and Pt nanosponges) for their applicability in the analyses of small analytes, peptides and proteins. 42 Au NPs were reported as the most suitable substrate for small analytes; for larger molecules, the Fe 2 O 3 and Pt nanosponges were demonstrated as the most efficient substrate allowing the detection of molecules up to 25 kDa. To increase the specificity toward an analyte, NP surface modification or conjugation with recognition biomolecules, such as aptamers, can be employed.…”

Nanomaterial-Assisted Laser Desorption Ionization for Mass Spectrometry-Based Biomedical Analysis

“…[50]. Shenar et al compared peptide LDI efficiency on supports of pencil lead, porous silica gel, DIOS-chip and NALDI ™ target, and showed that chromashowed that chromaed that chromatography porous silica gel was more attractive than existing reference supports for sensitive peptide detection [51].…”