Electrospray ionization (ESI) mass spectrometry (MS) has proven to be an extremely powerful technique for studying the stoichiometry and binding strength of peptide-metal complexes. We have found a significant new problem in the ESI-MS of zinc-peptide systems involving the deposition of zinc in the ESI emitter. This deposition of zinc during the experiment removes a significant amount of zinc ions from the solution, impacting the resulting mass spectral intensities used to quantify the amount of the zinc-bound species. Analysis of infused zinc-peptide samples with atomic absorption spectrometry and with a custom-built nanoflow ESI source confirms the alteration of the analyte solutions with positive or negative or no potential applied to the emitter. Ultimately, the location of the zinc deposition was determined to be the stainless steel emitter. The use of a custom-built nanoESI interface using glass emitters was found to mitigate the zinc deposition problem. The phenomenon of metal deposition warrants further investigation as it may not be limited to just zinc and may represent a significant obstacle in the ESI-MS analysis of all protein-metal systems.

电喷雾电离 (ESI) 质谱 (MS) 已被证明是研究肽-金属配合物的化学计量和结合强度的极其强大的技术。我们在锌肽系统的 ESI-MS 中发现了一个重要的新问题，涉及锌在 ESI 发射器中的沉积。实验期间锌的这种沉积从溶液中去除了大量的锌离子，影响了用于量化锌结合物质数量的所得质谱强度。使用原子吸收光谱法和定制的纳米流 ESI 源对注入的锌肽样品进行分析，证实了分析物溶液的变化，对发射器施加正电位或负电位或无电位。最终，锌沉积的位置被确定为不锈钢发射器。发现使用使用玻璃发射器的定制 nanoESI 接口可以缓解锌沉积问题。金属沉积现象值得进一步研究，因为它可能不仅限于锌，而且可能是所有蛋白质-金属系统的 ESI-MS 分析中的一个重大障碍。