Nanodiamond MALDI support for enhancing the credibility of identifying proteins

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a standard analytical tool for protein identification and peptide sequencing. High sensitivity and resolution are two critical parameters for recording good peptide mass fingerprinting (PMF) of low abundance proteins. Here, we report a novel nanodiamond (ND) (normal size 3-10 nm) support for MALDI-MS target, over which α-cyano-4-hydrocinnamic acid (CCA) crystallizes evenly. Good reproducibility of relative peak intensity (R.S.D. less than 11.8%) among sample spot (from ring to center) is achieved on ND support. Therefore, the search for “hot spots” during the analysis is not necessary, which is supporting for the automatic acquisition of data. Due to high absorbability of energy from the laser, the ND support improves ionization efficiency of samples. In general, the sensitivity of MS obtained on ND support can be enhanced three to four times compared to the conventional MALDI sample preparation technique. Sensitivity obtained on ND support ranges from 62.5 amol of Arg-vasopressin standard peptide to 1.0 fmol of myoglobin tryptic peptide mixture. Reduced spot size and increased sensitivity in MALDI-MS are also accomplished by ND support. With spot size reduced, the signal intensity of cytochrome c (Cyt c) tryptic peptide obtained on ND support is at least seven times greater than it acquired on stainless steel. And ND support has been found better tolerance for salt (up to 500 mM NaCl) to MALDI-MS analysis. All these properties make ND support a valuable tool for MALDI-MS identification of proteins.