Chen Wei-Yu, Chen Yu-Chie
Department of Applied Chemistry, National Chiao Tung University, Hsinchu 300, Taiwan.
Anal Chem. 2007 Nov 1;79(21):8061-6. doi: 10.1021/ac0709450. Epub 2007 Sep 29.
The presence of alkali cation adductions of oligonucleotides commonly deteriorates matrix-assisted laser desorption/ionization (MALDI) mass spectra. Thus, desalting is required for oligonucleotide samples prior to MALDI MS analysis in order to prevent the mass spectra from developing poor quality. In this paper, we demonstrate a new approach to extract traces of oligonucleotides from aqueous solutions containing high concentrations of salts using microwave-assisted extraction. The C18-presenting magnetite beads, capable of absorbing microwave irradiation, are used as affinity probes for oligonucleotides with the addition of triethylammonium acetate as the counterions. This new microwave-assisted extraction approach using magnetite beads as the trapping agents and as microwave-absorbers has been demonstrated to be very effective in the selective binding of oligonucleotides from aqueous solutions. The extraction of oligonucleotides from solutions onto the C18-presenting magnetite beads takes only 30 s to enrich oligonucleotides in sufficient quantities for MALDI MS analysis. After using this desalting approach, alkali cation adductions of oligonucleotides are dramatically reduced in the MALDI mass spectra. The presence of saturated NaCl (approximately 6 M) in the oligonucleotide sample is tolerated without degrading the mass spectra. The detection limit for d(A)6 is approximately 2.8 fmol.
寡核苷酸的碱金属阳离子加合物的存在通常会使基质辅助激光解吸/电离（MALDI）质谱图质量下降。因此，在进行MALDI MS分析之前，寡核苷酸样品需要脱盐，以防止质谱图质量变差。在本文中，我们展示了一种新方法，即利用微波辅助萃取从含有高浓度盐的水溶液中提取痕量寡核苷酸。带有C18的磁铁矿珠能够吸收微波辐射，在添加乙酸三乙铵作为抗衡离子的情况下，用作寡核苷酸的亲和探针。这种以磁铁矿珠作为捕获剂和微波吸收剂的新型微波辅助萃取方法，已被证明在从水溶液中选择性结合寡核苷酸方面非常有效。将寡核苷酸从溶液中萃取到带有C18的磁铁矿珠上仅需30秒，就能富集足够量的寡核苷酸用于MALDI MS分析。使用这种脱盐方法后，寡核苷酸的碱金属阳离子加合物在MALDI质谱图中显著减少。寡核苷酸样品中存在饱和NaCl（约6 M）时，质谱图质量不受影响。d(A)6的检测限约为2.8 fmol。
