We report the soft laser extraction and production of highly charged peptide and protein ions for mass spectrometry directly from bulk liquid water at atmospheric pressure and room temperature, using picosecond infrared laser ablation. Stable ion signal from singly charged small molecules, as well as highly charged biomolecular ions, from aqueous solutions at low laser pulse fluence (∼0.3 J cm^–2) is demonstrated. Sampling via single picosecond laser pulses is shown to extract less than 27 pL of volume from the sample, producing highly charged peptide and protein ions for mass spectrometry detection. The ablation and ion generation is demonstrated to be soft in nature, producing natively folded proteins ions under sample conditions described for native mass spectrometry. The method provides laser-based sampling flexibility, precision and control with highly charged ion production directly from water at low and near neutral pH. This approach does not require an additional ionization device or high voltage applied directly to the sample.

中文翻译：

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柔和的皮秒红外激光从散装液态水中提取高电荷的蛋白质和多肽，用于质谱分析

我们报道了使用皮秒红外激光烧蚀直接从大容量液态水在常压和室温下进行的软激光提取以及用于质谱的高电荷肽和蛋白质离子的生产。来自低电荷激光脉冲通量（〜0.3 J cm ^–2）的水溶液中的单电荷小分子以及高电荷生物分子离子的稳定离子信号）进行了演示。通过单皮秒激光脉冲进行的采样显示从样品中提取的体积少于27 pL，从而产生了用于质谱检测的高电荷肽和蛋白质离子。已证明消融和离子产生本质上是软的，在描述用于天然质谱的样品条件下产生天然折叠的蛋白质离子。该方法提供了基于激光的采样灵活性，精度和控制能力，可直接从低pH值和接近中性pH的水中产生高电荷的离子。这种方法不需要额外的电离设备或直接将高压施加到样品上。