Cheng S W, Chan T W
Department of Chemistry, The Chinse University of Hong Kong.
Rapid Commun Mass Spectrom. 1996;10(8):907-10. doi: 10.1002/(SICI)1097-0231(19960610)10:8<907::AID-RCM576>3.0.CO;2-K.
Four ammonium salts, NH4F, NH4Cl, NH4Br and NH4I were tested as co-matrices for the matrix-assisted laser desorption/ionization (MALDI) analysis of a number of DNA homopolymers, including phosphorylated d(T)8, d(A)4, d(C)4 and non-phosphorylated d(G)4, using 2-amino-5-nitropyridine (ANP) matrix. In the present study, all the ammonium halides displayed significant enhancement effects on the signal intensities of the intact molecular ions of the DNA homopolymers. Among the halides used, NH4F was found to exhibit the greatest enhancement effects. By comparison with results obtained using the corresponding isomorphous potassium halides as co-matrices, it is postulated that both the cationic and anionic portions of the co-matrix molecule play important roles in the desorption/ionization of the oligonucleotides under typical MALDI conditions. It was also demonstrated that the ANP matrix exhibits a strong inhibitory effect on the formation of alkali-metal adducts in oligonucleotide analysis.
以2-氨基-5-硝基吡啶（ANP）为基质，测试了四种铵盐NH4F、NH4Cl、NH4Br和NH4I作为共基质用于多种DNA同聚物的基质辅助激光解吸/电离（MALDI）分析，这些DNA同聚物包括磷酸化的d(T)8、d(A)4、d(C)4以及未磷酸化的d(G)4。在本研究中，所有卤化铵对DNA同聚物完整分子离子的信号强度均表现出显著的增强作用。在所使用的卤化物中，发现NH4F表现出最大的增强效果。通过与使用相应同晶型卤化钾作为共基质所获得的结果进行比较，推测共基质分子的阳离子部分和阴离子部分在典型MALDI条件下对寡核苷酸的解吸/电离均起着重要作用。还证明了ANP基质在寡核苷酸分析中对碱金属加合物的形成具有强烈的抑制作用。
