Specific enrichment of phosphopeptides by using magnetic nanocomposites of type Fe 3 O 4 @graphene oxide and Fe 3 O 4 @C
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ORIGINAL PAPER
Specific enrichment of phosphopeptides by using magnetic nanocomposites of type Fe3O4@graphene oxide and Fe3O4@C coated with self-assembled oligopeptides Nan Li 1 & Li Zhang 1 & Hailan Shi 1 & Jianru Li 1 & Jing Zhang 1 & Zhiqi Zhang 1 & Fuquan Dang 1 Received: 19 August 2019 / Accepted: 26 December 2019 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Iron(III-immobilized magnetic nano-composites (MNCs) were first fabricated using one-step aqueous self-assembly of oligopeptides (Glu-Pro-Ala-Lys-Ala-Lys-Ala-Lys; EPAK-VI) for the highly selective capture of phosphopeptides from complex biological samples. Under physiological conditions, EPAK-VI can readily self-organize into a robust and complete coating layer mainly composed of β-sheets and β-turns on the surface of Fe3O4@GO and Fe3O4@C MNCs. Tailored by the cyclic structure of proline, the Glu-Pro motifs of EPAK-VI are vertically erected on the surface and thus serve as an effective linker to chelate Fe3+ through carboxyl (COO-) group in the glutamic acid (E) residues. The ionic hydrogen bonds between the ε-amino groups and the surface negative charges coupled with intermolecular hydrogen bonds render the EPAK-VI coating on the MNCs insusceptible to repeated extreme washing conditions. The Fe3+-EPAK-VI coated MNCs exhibit high enrichment efficiency for β-casein tryptic digest (0.05 fmol μL−1), excellent selectivity from mixed digests (β-casein/bovine serum albumin, mass ratio 1:500), and high recovery rate (over 80%). Keywords Nanocomposite . Self-assembly . Oligopeptide . Enrichment . Phosphopeptide
Introduction Protein phosphorylation plays crucial roles in cell signalling, cell proliferation and differentiation, cell apoptosis, protein trafficking, epigenetic control, and metabolic pathways [1–4]. Mass spectrometry (MS)-based techniques are crucial for the identification of phosphorylation sites and quantification of their dynamic changes owing to the ultrahigh sensitivity, wide dynamic range, and superior analytical speed [5–9]. However, the low abundance and ionization efficiencies of phosphopeptides/proteins, low dynamic stoichiometry, and
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-019-4096-z) contains supplementary material, which is available to authorized users. * Fuquan Dang [email protected] 1
Key Laboratory of Analytical Chemistry for Life Science of the Shaanxi Province School of Chemistry and Chemical Engineering, Shaanxi Normal University, 620 West Chang’an Street, Xi′an 710119, China
signal suppression of counterparts in the presence of interference proteins and nonphosphopeptides hinder the comprehensive identification and recognition of phosphorylated sites in MS analysis [10–14]. Therefore, it is required to design and fabricate functional antifouling materials for sample pretreatment and selective enrichment from complex mixtures prior to the MS analysis. Numerous strategies, such as ion-exchange chromatography [15], immune affinity capture [4]
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