| Abstract
| - The alkali cation adductions of oligonucleotides dramatically degrade MALDI mass spectra and even affect thedetection limit. Desalting is generally involved in MALDIsample preparation. This work demonstrates the feasibility of using 3,4-diaminobenzoic acid (DABA) and 3,5-DABA as the MALDI matrix for oligonucleotide analysis.Furthermore, sodium ion adducts of oligonucleotideswere simultaneously reduced in the mass spectra whenDABA was used as the MALDI matrix and sol−gel material was used as the sample support. However, depositingthe sample on the sample support was very difficult, andthe lack of homogeneity of analytes/matrix distributionon the sample support also led the analyte signals to berevealed only in “sweet spots”. Alternatively, DABA wasdoped into sol−gel materials to generate homogeneousDABA/sol−gel hybrid film. The DABA/sol−gel hybrid filmwas used as the sample substrate to assist the desorption/ionization of analytes. The analyte signals were evenlyfound on the sample substrate. The sodium ion adductions of oligonucleotides were also effectively suppressed.The sample preparation used in this approach resemblesthat used in the authors' previous study, involving sol−gel-assisted laser desorption/ionization (SGALDI) massspectrometry (Lin, Y.-S.; Chen, Y.-C. Anal. Chem. 2002,74, 5793−5798.) The SGALDI approach was demonstrated to be effective in assisting the desorption/ionization of peptides and small proteins. Herein, the SGALDImaterial, DABA/sol−gel hybrid material, was successfullyapplied to oligonucleotide analysis, and good-quality massspectra were obtained without extra desalting. Additionally, the presence of 0.1% SDS in the oligonucleotidesample solution was tolerated without degrading the massspectra. The largest detectable molecular size for oligonucleotides was 72 mer. The detection limit for 24 merof oligonucleotide was 20 fmol.
|
