Nanodiamond-based two-step sampling of multiply and singly phosphorylated peptides for MALDI-TOF mass spectrometry analysis

• Published in: Analyst (London) 2011-05, Vol.136 (9), p.1922-1927
• Main Authors: KAI JUNG SHIAU, HUNG, Shain-Un, LEE, Hsiao-Wen, WU, Chih-Che
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Analytical chemistry; Animals; Caseins - chemistry; Caseins - isolation & purification; Cattle; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Humans; Molecular Sequence Data; Nanodiamonds - chemistry; Other chromatographic methods; Peptides - chemistry; Phosphopeptides - analysis; Phosphorylation; Serum Albumin, Bovine - chemistry; Serum Albumin, Bovine - isolation & purification; Spectrometric and optical methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Titanium - chemistry; Trypsin - chemistry
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c0an01046d

Simultaneous detection of multiply and singly phosphorylated peptides using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is challenging because of suppression effects during ionization. In oder to overcome this problem, this study presents a new approach to improve the detection of phosphopeptides by stepwise enrichment using polyarginine-coated (PA-coated) and titanium dioxide-coated (TiO(2)-coated) nanodiamonds for fractionation of multiply and singly phosphorylated peptides prior to on-probe MALDI MS analysis. The feasibility of this approach was demonstrated using synthetic peptides containing different numbers of phosphate groups, tryptic digests of α-casein, β-casein, and complex protein mixtures. The high specificity of the approach is shown in its effective enrichment and fractionation of phosphopeptides from the digest of β-casein and bovine serum albumin at a molar ratio as low as 1 : 1000, which out-performs the commercial Fe(3+)-IMAC and TiO(2) isolation kits. It offers a simple and effective alternative for the fractionation and identification of multiply and singly phosphorylated peptides by MALDI MS and allows for deduction of more information from limited starting materials.