Using Surface-Assisted Laser Desorption/Ionization Mass Spectrometry to Detect Proteins and Protein–Protein Complexes

Abstract

In this study, we combined surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) with HgTe nanostructures as matrix for the detection of several proteins (α1-antitrypsin, trypsin, IgG, protein G) and their complexes. We investigated the effects of several parameters (the concentration and nature of surfactants and metal ions, the pH, and concentration of the analytes in the sample matrixes) on the sensitivity of the detection of these proteins and their complexes. The presence of stabilizing Brij 76 surfactant and Zn(II) ions allowed the detection of weak protein complexes, such as α1-antitrypsin-trypsin and IgG-protein G complexes, at the picomole level. We observed multiply charged states at m/z 72,160 ([α1-antitrypsin + trypsin + H](+)) and 86,585 ([IgG + protein G + 2H](2+)) for the α1-antitrypsin-trypsin and IgG-protein G complexes, respectively. To the best of our knowledge, detection of weak protein complexes and determination of their stoichiometry have not been demonstrated previously when a combination of SALDI-MS and nanostructures were used. This simple and reproducible SALDI-MS approach using HgTe nanostructures holds great potential for the detection of other proteins and their complexes.

Commercial Silicon-on-Insulator (SOI) Wafers as a Versatile Substrate for Laser Desorption/Ionization Mass Spectrometry

“…However, while the presence of citric acid was particularly useful for peptides with large masses (93000 Da), the LDI efficiency was slightly degraded for peptides with smaller masses (G2000 Da) (Figure 2b). The addition of ammonium hydrogen citrate (dibasic) [6] and other acids such as trifluoroacetic acid and acetic acid did not result in any noticeable improvement in the LDI performance.…”

“…Various additives that have been reported to improve the LDI efficiency, including citric acid [14] and citrates [6], were tested. In particular, the addition of citric acid was found to enhance the performance of LDI on SOI wafers.…”

“…Various nanostructured surfaces have been successfully demonstrated for LDI of thermally labile molecules, with examples that include nanostructured Si surfaces (DIOS: desorption/ionization on porous Si) [2,3], titania nanotube arrays [4], nanostructured gold thin films [5], HgTe nanostructures [6], and many more. In previous studies, the use of the surface nanostructures featured a common strategy in the creation of efficient LDI on the surfaces, although the role of the nanostructures involved in the LDI process has not yet been fully understood.…”

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

“…A nanostructure initiator development study involving instant release of the trapped initiator molecules (e.g., 14 kDa poly(3,3,3-trifluoropropylmethylsiloxanes) from silicon pores expanded the protein mass detection range to 30 kDa [60]. It is possible that the success of these approaches lies in more abundant matrix plumes due to the relatively low NP surface melting temperature (HgTe NP, 873K, compared with Au 1337K) or due to release of neutral molecules trapped in nanostructure [60,61]. Figure 5a demonstrates that the NPCA-NaOH matrix effectively desorbs/ionizes high molecular mass polymers such as 25 and 80 kDa PDMS.…”

Tea Identification through Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

“…Several nanomaterials, including Au [9][10][11], Ag [12], carbon nanotubes [13], SiO 2 [14], TiO 2 [15], HgTe nanostructures [16][17][18], and Fe 3 O 4 [19], have been employed in SALDI-MS. These NPs absorb energy from laser irradiation and then transfer it to the analytes to induce desorption and ionization.…”