Goodlett D R, Camp D G, Hardin C C, Corregan M, Smith R D
Chemical Sciences Department, Pacific Northwest Laboratories, Richland, Washington 99352.
Biol Mass Spectrom. 1993 Mar;22(3):181-3. doi: 10.1002/bms.1200220307.
In 10 mM sodium phosphate, pH 7.6, containing 0.1 mM ethylenediaminetetraacetic acid, ions correspondings to the non-calent, four-stranded oligonucleotide, d(CGCG4GCG)4, were detected by negative ion electrospray ionization (ESI) mass spectrometry at a low nozzle-skimmer (delta NS) bias (-150 V), but not at a higher delta NS bias (> -250 V). In contrast, when the sample was desalted and analyzed by ESI mass spectrometry at a low delta NS bias only ions for the single-stranded d(CGCG4GCG) species were observed. These data agree with spectroscopic evidence which showed that oligonucleotides with the sequence motif 5'd(CGCGnGCG)3', where n = 2-5, formed stable four-stranded complexes in the presence of monatomic cations, like K+, Ca2+, Na+ and Li+, but not in their absence.
在含有0.1 mM乙二胺四乙酸的10 mM磷酸钠（pH 7.6）中，通过负离子电喷雾电离（ESI）质谱在低喷嘴 - 分离器（delta NS）偏压（-150 V）下检测到了与非共价四链寡核苷酸d(CGCG4GCG)4对应的离子，但在较高的delta NS偏压（> -250 V）下未检测到。相反，当样品脱盐并在低delta NS偏压下通过ESI质谱分析时，仅观察到单链d(CGCG4GCG)物种的离子。这些数据与光谱证据一致，光谱证据表明，具有5'd(CGCGnGCG)3'序列基序的寡核苷酸（其中n = 2 - 5）在存在单原子阳离子（如K +、Ca2 +、Na +和Li +）时形成稳定的四链复合物，而在不存在这些阳离子时则不形成。
