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首页> 外文期刊>Journal of mass spectrometry: JMS >Ionic strength of electrospray droplets affects charging of DNA oligonucleotides
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Ionic strength of electrospray droplets affects charging of DNA oligonucleotides

机译：电喷雾液滴的离子强度会影响DNA寡核苷酸的充电

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摘要

The fundamental aspects of charging in electrospray ionization (ESI) are hotly debated. In the present study, ESI charging of DNA oligonucleotides was explored in both positive (ESI+) and negative (ESI-) polarity using mass spectrometry detection. Single-stranded 12-mer CCCCAATTCCCC in buffer solution (aqueous NH_4Ac, 100mM) produced similar charge state distribution (CSD) in either ESI+ or ESI-. Similarity of CSD in ESI+ and ESI- was also observed for the double-stranded 12-mer CGCGAATTCGCG. By adding typical low-vapor reagents (e.g. m-nitro benzyl alcohol, m-NBA; sulfolane) into the same buffer solution (<0.5% w/v), both CCCCAATTCCCC and CGCGAATTCGCG revealed strong supercharging (SC) effect in ESI-, while very little or no SC effect was observed in ESI+. With either sulfolane or m-NBA, the CGCGAATTCGCG duplex dissociated into single strands in ESI-. No SC was observed in both ESI+ and ESI- for thermally denatured CGCGAATTCGCG duplex in NH_4Ac buffer without the reagents. These findings are difficult to reconcile with the earlier model, which attributes SC in aqueous buffer solution to the conformational changes of analytes. Our observations suggest that the ionic strength of ESI droplets strongly affects the CSD of biopolymers such as DNA oligonucleotides and that SC effect is related to the depletion of ionic strength during the ESI process.
机译：电喷雾电离（ESI）中充电的基本方面引起了激烈的争论。在本研究中，使用质谱检测技术以正（ESI +）和负（ESI-）极性探索了DNA寡核苷酸的ESI充电。缓冲溶液（NH_4Ac，100mM水溶液）中的单链12聚体CCCCAATTCCCC在ESI +或ESI-中产生相似的电荷状态分布（CSD）。对于双链12聚体CGCGAATTCGCG，在ESI +和ESI-中也观察到CSD的相似性。通过在相同的缓冲溶液（<0.5％w / v）中添加典型的低蒸汽试剂（例如间硝基苄醇，m-NBA，环丁砜），CCCCAATTCCCC和CGCGAATTCGCG均显示出ESI-中的强增压（SC）效果，而在ESI +中几乎没有观察到SC效应。使用环丁砜或m-NBA，CGCGAATTCGCG双链体在ESI-中解​​离成单链。在没有试剂的NH_4Ac缓冲液中，热变性CGCGAATTCGCG双链体在ESI +和ESI-中均未观察到SC。这些发现很难与早期模型相吻合，后者将缓冲水溶液中的SC归因于分析物的构象变化。我们的观察结果表明，ESI小滴的离子强度强烈影响生物聚合物（如DNA寡核苷酸）的CSD，而SC效应与ESI过程中离子强度的消耗有关。

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